P.O. Box 2057
Lake
Placid, Florida 33862 USA Phone: 863-465-2571
FAX:
863-699-1927 Email: archbold@archbold-station.org
Archbold Biological
Station
P.O. Box 2057 Lake
Placid, Florida 33862 USA
Phone: 863-465-2571 FAX:
863-699-1927
Email: archbold@archbold-station.org
|
Current
Research at Archbold Biological Station, 11 - 12 January 2001 Symposium Organizers: Group Photo | Schedule | Contents | Abstracts Group Photo, 4th Archbold Symposium, 11 January 2001. photo by Tina Fleischer THURSDAY, JANUARY 11 Morning Session (Auditorium)
9:30 William E. Conner*, R. Boada, F. C. Schroeder, A. González, J. Meinwald, and T. EisnerChemical ecology of the scarlet-bodied wasp moth, Cosmosoma myrodora (Lepidoptera, Arctiidae) 10:00 BREAK (Dining Room) 10:30 William A. Watts* and E. C. GrimmFlorida sinkholes and the Lake Wales Ridge 11:00 Eric C. Grimm* and W. A. WattsLate-glacial flora and climate recorded at Lake Annie and Lake Tulane, Florida 11:30 Samuel D. Marshall*, K. Thornburg, and W. Hoeh Phylogenetic analyses of molecular and morphological traits indicate new species and new patterns of divergence for Florida’s Geolycosa wolf spidersLUNCH (Dining Room) Afternoon Session (Auditorium)
FRIDAY, JANUARY 12 Morning Session (Auditorium)
SEMINAR ABSTRACTS -- LISTED IN CHRONOLOGICAL ORDER THURSDAY, JANUARY 11 Morning Session "Episodic reproduction in two fire-prone palms, Serenoa repens and Sabal etonia." Warren G. Abrahamson, Bucknell University, Lewisburg PA 17837, and Archbold Biological Station This long-term study examined how fire events affected the flowering of two native palms in a fire-prone environment. By examining how flowering varied across vegetative associations, I determined whether plant size or mass influenced flowering, whether canopy openness or increased soil fertility following fire enhanced flowering, and whether potential flowering stimuli interact. Individuals of the widespread Serenoa repens and narrow endemic Sabal etonia were monitored (for a total of 9,900 plant-yr records) for growth performance and reproduction in flatwoods, scrubby flatwoods, sand-pine scrub, and sandhill that were affected by single or multiple fires. In addition, clipping, fertilizing, and clipping and fertilizing experiments were conducted in three vegetative associations to simulate the effects of fire in order to ascertain which stimuli and their interactions encourage flowering episodes. Both species exhibited marked resiliency to fire, rapidly resprouting from extensive underground stores. The frequencies of leaf production and flowering increased dramatically following fire in all vegetative associations compared to preburn periods, but especially in long-unburned (> 60 yr) associations with substantial preburn overstory canopies. Strong episodic flowering responses were triggered after each of three repeated burns conducted during an 8-yr period at a previously long-unburned sandhill. Size, and hence estimated mass, were significant predictors of whether a palm would flower and if so, how much it flowered. The loss of a palm’s crown by fire, or by clipping, stimulated flowering but this effect was mediated by light availability. Palms under more complete overstory canopies flowered less than those in light gaps or at open-canopied stands. Fertilization of palms, intended to simulate greater post-fire nutrient availabilities, did not stimulate flowering. Logistic regression models were developed for each palm species to estimate the probability of flowering in each vegetative association. These models accurately predicted flowering and non-flowering individuals. However, probability of flowering models that were generalized across vegetative associations for each species were less accurate than the association-specific models which suggests the specific nature of flowering responses. These long-lived palms are well adapted to fire but are highly vulnerable to human-caused disturbance because of their very limited ability to recolonize former habitats. "Chemical ecology of the scarlet-bodied wasp moth, Cosmosoma myrodora (Lepidoptera, Arctiidae)." William E. Conner*, Ruth Boada*, Frank C. Schroeder†, Andrés González‡, Jerrold Meinwald†, and Thomas Eisner‡§ *Dept. of Biology, Wake Forest University, P.O. Box 7325, Winston- Salem, NC 27109, †Dept. of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, and ‡ Dept. of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853 Males of the moth, Cosmosoma myrodora (Arctiidae), acquire pyrrolizidine alkaloid by feeding on the excrescent fluids of certain plants (for instance, Eupatorium capillifolium). They incorporate the alkaloid systemically, and as a result are protected against spiders. The males have a pair of abdominal pouches, densely packed with fine cuticular filaments, which in alkaloid-fed males are alkaloid-laden. The males discharge the filaments in bursts upon the female during courtship, embellishing her with alkaloid as a result. The topical investiture protects the female against spiders. Alkaloid-free filaments, from alkaloid-deprived males, convey no such protection. The males also transmit alkaloid to the female by seminal infusion. The systemic alkaloid thus received, which itself may contribute to the female's defense against spiders, is bestowed in part by the female upon the eggs. While paternal contribution to egg defense had previously been demonstrated for several arctiid moths, protective nuptial festooning of a female by its mate, such as is practiced by C. myrodora, appears to be without parallel among insects. "Florida sinkholes and the Lake Wales Ridge." W.A. Watts, Trinity College, Dublin 2, Ireland, and E.C. Grimm, Research and Collections Center, Illinois State Museum, Springfield, IL 60703 The Florida Peninsula has numerous sinkhole lakes caused by solution of the underlying limestone. Lake Annie on the Archbold Station and Lake Tulane in Avon Park are good examples from the Lake Wales Ridge. Sinkhole lakes vary greatly in size and morphology, from nearly circular in shape to very irregular, recording coalescence of groups of small lakes. Lakes may contain thick sediments which contain fossil pollen and macrofossils from which past vegetation and climate histories can be reconstructed. Water levels in the lakes appear to be correlated with changing sea-level. At the end of the Last Glaciation, the water table fell to about 18m. below the present level with the result that most modern lakes were dry basins which first began to approach modern water levels about 8,500 years ago. Deep lakes such as Annie and Tulane continued to sediment during the Last Glaciation and provide a record of the vegetation of that time. They record water level fluctuations and changes in vegetation cover which can be correlated with world-wide climatic events. Investigation of sinkholes increasingly reveals that they may be complex structures. In some cases the apparent base of a sinkhole has proved to seal further organic deposits of unknown age below. Further, the centre of sedimentation within the sinkhole may change within a basin so that the apparent modern deepest point does not indicate where the oldest sediments lie. Sinkholes may become extinct by filling up with sediment. Some such are of great age. At Peace Creek near Bartow, a deep sinkhole (60m.) proved to be of Pliocene age. It reveals a flora with much in common with the present. The swamp and aquatic flora is species-rich and very similar to today’s. Upland forest is also similar with the addition of some now regionally extinct genera such as Pterocarya in the walnut family. There is no evidence for the presence of significant tropical elements. Most distinctive is the much stronger development of dry prairie-like upland vegetation in the Holocene and Last Glaciation than in the Pliocene. Tentatively, the dry vegetation of sand hills and fossil dunes on the Lake Wales Ridge is, geologically, a relatively young development. "Late glacial flora and climate recorded at Lake Annie and Lake Tulane, Florida." Eric C. Grimm, Illinois State Museum, Research and Collections Center, 1011 East Ash Street, Springfield, IL 62703, grimm@museum.state.il.us, and William A. Watts, Dept. of Botany, Trinity College, Dublin 2, Ireland, wwatts@tcd.ie Pollen and macrofossil records from Lake Annie on the Archbold Biological Station and Lake Tulane in Avon Park, Florida provide history of vegetation and climate change for the last 60,000 years. A new 18-m core from Lake Annie provides a detailed record for the past 14,000 years. The Lake Tulane record shows rapid switches between pine forest and oak savanna during marine isotope stages 3 and 2. The pine phases correspond with the Heinrich (H) events in the north Atlantic, during which, massive surges of icebergs deposited distinctive ice-rafted debris into north Atlantic sediments. Temperatures were cold in the north Atlantic region, and conveyor belt, a major ocean current transporting water and heat to the north Atlantic, shut down. Macrofossil evidence from Lake Tulane indicates that water levels were lower during the oak-savanna phases. A quantitative analysis of the pollen data shows that vegetation during the Heinrich events was similar to the late Holocene, implying a warm, wet climate. Thus, the H events in Florida regions were wet and warm, rather than cool. Perhaps the shutdown of the conveyor belt, which normally transports heat away from the subtropics, resulted in climate warming in this region. The Lake Annie record shows a sudden increase in water depth at the beginning of the Younger Dryas (YD) about 12,800 years ago. The sediment changes from a shallow-water peat to a deeper water gyttja. Similar to the H events, the YD was a cold episode in the north Atlantic region. However, in southern Florida, pine increased, and climate was wet and warm. Thus, the YD was similar to the H events. The vegetation of the early Holocene, an open pine-oak savanna, was different from Pleistocene and late Holocene vegetation. About 6000 years ago, pine increased and the modern vegetation of the Archbold region developed. "Phylogenetic analyses of molecular and morphological traits indicate new species and new patterns of divergence for Florida's Geolycosa wolf spiders." S. D. Marshall*, K. Thornburg†, and W. Hoeh†. *J. H. Barrow Field Station, Hiram College, Hiram, OH 44234, †Dept. of Biological Sciences, Kent State University, Kent, OH 44242 Currently, 15 species of Geolycosa have been described based on a limited number of morphological characteristics. The state of Florida has nine Geolycosa sp., seven living in scrubs and sandhills across the state. The goals of this project are to (1) estimate the evolutionary relationships among Floridian Geolycosa populations and species using comparisons of cytochrome c oxidase subunit I (COI) DNA sequences and morphological traits, and (2) use the hypothesized relationships to infer the historical patterns of the evolutionary diversification of Geolycosa across the state. Geolycosa individuals from a total of 33 Florida scrub sites were collected and identified based on morphological characteristics. Total DNAs from 74 individuals representing the species G. escambiensis, G. micanopy, G. patellonigra, G. x. xera, G. x. archboldi, G. hubbelli, G. ornatipes, G. wrighti, G. missouriensis, G. rafaelana, G. turricola, and G. pikei were extracted and a portion (ca. 710 base pairs) of the COI gene amplified using the polymerase chain reaction. To date, the COI fragments from 38 individuals representing 11 species of Geolycosa have been cycle sequenced. Preliminary phylogenetic analyses of the COI sequences and morphological traits suggest that (1) Floridian Geolycosa are not a monophyletic assemblage, (2) G. xera, G. escambiensis, G. hubbelli, G. patellonigra, and G. micanopy are not valid species in a phylogenetic sense, and (3) the two distinct ecotypes of Geolycosa have evolved repeatedly across the state. We also found that the patterns of phylogeographic divergence different from those previously proposed. Earlier models for the patterns of diversification of Floridian Geolycosa proposed that scrub Geolycosa are the descendants of Atlantic coastal species, which diverged on the interglacial islands that comprised the ancient Florida peninsula in a north-south pattern. We found evidence that the Geolycosa of the entire eastern USA are derived from ancestors in the western Panhandle, and that the pattern of divergence within Florida occurred from west to east. Afternoon Session "Behavioral ecology of Blue Jays in citrus groves: do Blue Jays depend on acorns from nearby woods?" Curtis S. Adkisson, Dept. of Biology, Virginia Tech, Blacksburg, VA 24060 Blue Jays (Cyanocitta cristata) inhabit the eastern deciduous forest of North America, where they cache large numbers of acorns, beechnuts, and chestnuts during September and October for use during the following winter and early spring. Earlier studies showed that as many as 3000 nuts may be cached by each jay in its primary home range. Not all nuts are consumed, and many germinate in microhabitats highly favorable to seedlings of Fagaceae. Near Archbold Biological Station most of the native scrub habitat has been replaced by citrus groves and other uses, but Blue Jays appear to thrive in most of the altered habitats. They seem scarce in citrus groves except in those within 0.5-1.0 km of a sizeable patch of oak woods or native scrub. More than 300 caching trips/hour into the groves south of Archbold Road in some years. Some jays fly considerably more than 1 km with nuts in the beak and throat, continuing across U. S. 27 an unknown distance into groves east of the highway. Since 1996, I have banded over 200 Blue Jays in the Reynolds and Keck groves south of Archbold Road in an effort to determine how many jays might be using grove habitat as their primary activity space. Some of these jays were fitted with transmitters in 1997, 1999, and 2000, in order to learn how many caching trips individuals make during a season (and therefore how many nuts might be cached), how much time they spend in grove and other nearby habitats, where they roost nightly, and where they spend most their time when not caching. These efforts have allowed me to revise upward the estimate of number nuts cached to as many as 5000/bird. I have also learned that the jays roost at night and spend the winter generally in the same immediate areas where they cache nuts. I suspect that they also nest in the restricted area defined by their caching activities. Blue Jays in these groves, therefore, appear to depend heavily on acorns (and perhaps also arthropods) obtained in the oak-pine habitats to the north and west of the grove, even though most of their time is spent in the grove. "Ecology meets psychology: what Florida Scrub-Jays understand about food objects." Jack P. Hailman, University of Wisconsin, Madison, WI, and Archbold Biological Station Two experiments explored what Florida Scrub-Jays (Aphelocoma coerulescens) understand about objects. (1) The first was adapted from a procedure devised by the famous Swiss developmental psychologist Jean Piaget to see at what age his own children came to understand that objects have a physical existence apart from the perception of them. I buried half a raw, shelled peanut in the sand in plain view of a family of jays to see if any bird would fly to the site and dig up the food, thus showing that the bird understood the object existed even when out of sight. In 9 of 10 families tested a jay dug up the buried peanut within the trial interval. (2) The second experiment tested for a considerably more difficult cognitive skill. A hand-tame jay was allowed to extract the nut from half a peanut, and while the bird was still on my hand, I turned the empty shell upside down. A few individuals clearly understood this was the same now-empty object, and on the very first trial either continued to wait on my hand or else flew off with the extracted nut. Most jays, however, pecked at the empty shell or tried to pull it out of my hand, giving up only when discovering the shell was empty. Almost all these jays learned, some in a few trials repeating the procedure and others taking dozens of trials, and thus ceased trying to open the empty shell. This apparent understanding of the constancy of the object when rotated was never forgotten, even when a jay was tested a year or two years later. Nevertheless, one individual definitely never learned the object constancy, and another was making no progress when it disappeared. The results of these two experiments show that most Florida Scrub-Jays have good cognitive abilities concerning objects, apparently matched only by parrots and other corvids among birds, and perhaps only by primates among mammals."Hormones and behavior in the cooperatively breeding Florida Scrub-Jay." Stephan J. Schoech, Dept. of Biology, University of Memphis, Memphis, TN 38152 Because multiple endocrine axes are known to mediate most aspects of an animal’s life, an examination of endocrine physiology can yield insight into the mechanisms that underlie behaviors. Although Florida Scrub-Jays are intriguing to a behavioral endocrinologist for a number of reasons, I will focus on just a couple of compelling issues. First, virtually all jays in the population delay reproduction for at least a year, and some individuals do not breed for several years. This poses the question: Are non-breeders physiologically capable of reproducing? To address this question I compared levels of reproductive hormones (i. e., hormones of the hypothalamo- pituitary- gonadal {HPG} axis, such as testosterone and estradiol) in breeders and non-breeding helpers across several breeding seasons. Although hormone titres are generally lower in non-breeders, their endocrine profiles are very similar to those of breeders. Another endocrine axis, that has been postulated to play a role in the reproductive inactivity of non-breeders, is the hypothalamo-pituitary-adrenal (HPA) axis that produces and secretes the avian stress hormone, corticosterone. If non-breeders as subordinates are socially stressed due to their status, they might have elevated titres of corticosterone which, in addition to its metabolic function, can negatively affect an animal’s reproductive behavior. However, the seasonal corticosterone profiles of non-breeders do not differ from those of breeders. It is, therefore, unlikely that non-breeders’ reproductive inactivity is mediated through the actions of corticosterone. Second, even though non-breeders don’t participate in nest building or incubating eggs, shortly after young are hatched they assist the breeding pair in provisioning the nestlings. Because the protein hormone prolactin mediates numerous parental behaviors across taxa, I compared prolactin levels in non-breeding helpers and breeders. Although absolute levels are lower in non-breeders than in breeders, peak titres in both groups are found when nestlings are present. Additionally, levels of prolactin in non-breeders varied with the amount of alloparental care that was expressed: helpers that delivered little or no food had lower prolactin levels than those that provisioned nestlings at a higher rate. These data are consistent with the hypothesis that helping behavior in Florida Scrub-Jays is mediated via the actions of prolactin."Composition and abundance of wading bird prey in drainage ditch wetlands at MAERC." D. H. Anderson, South Florida Water Management District, West Palm Beach, FL, M. Baber, Florida International University, Miami, FL, M. McMillian, Archbold Biological Station, and G. Aborn, Archbold Biological Station During the last century, drainage ditch networks have replaced many large wetlands on the south Florida landscape, and these networks serve some of the functions of the historic wetlands such as supporting a food web that includes wading birds. At MAERC, a long-term study (1989-2000) recorded 15 species of wading birds using drainage ditches, and most of these species typically feed on small fish, amphibians and large invertebrates. We quantified the prey available to wading birds in these ditches with monthly throw trap (area = 0.25 m2) samples for one year. Total prey density did not show a strong seasonal pattern and averaged 56 individudals/m2 for the year. Most taxa were rare, and only six accounted for at least 5% of mean annual abundance. Thirty-six percent of annual density was accounted for by mosquito fish (Gambusia holbrooki), 23% by the least killifish (Heterandria formosa), 10% by tadpoles of the southern leopard frog (Rana utricularia), 6% by dragonfly naiads (Libellulidae), and 5% each by the Everglades crayfish (Procambarus alleni) and grass shrimp (Palaemonetes paludosa). We also collected two exotic species of fish the black acara (Cichlosoma bimaculatum) and the walking catfish (Clarias batrachus), which accounted for 0.3% and 0.2% of annual density. These preliminary results indicate that the prey community available to wading birds in drainage ditches is similar to that in more natural wetlands. "Reversal of pollination mutualism between yuccas and yucca moths: testing an Out of Florida hypothesis." Olle Pellmyr, Kari A. Segraves and David M. Althoff, Dept. of Biology, Vanderbilt University, VU Stn B Box 351812, Nashville TN 37212 Mutually beneficial relationships between species, such as plant-pollinator and plant-seed disperser interaction, are very common in all communities, and considered important both for ecological dynamics and for diversification and speciation. Such mutualisms often attract parasites that exploit the resources needed for maintenance of the mutualism. The origin of such parasites and their impact on the stability is relatively poorly understood. In a few cases, the parasitic species have indeed evolved from the mutualists. For example, obligate mutualisms such as those involving seed-eating pollinators have on a few occasions given rise to non-mutualist species. These systems are relatively simple and provide models for identifying factors that facilitate the evolutionarily stable reversal of a mutualistic interaction.Yuccas and yucca moths are one of the classical examples of obligate mutualism based on seed-parasitic pollinators. The moths serve as the exclusive pollinators of yuccas, and in return their larvae eat some of the developing seeds. In recent years, we have discovered that non-pollinating cheater yucca moths exist. One of the two documented cheater yucca moth species appear to have evolved quite recently from a pollinating ancestor endemic to a Pleistocene refugium in Florida. Based on systematic, ecological, behavioral, and phylogenetic data, we can now reconstruct in some detail the history of diversification of the yucca moths over the past ~40 million years. The resulting scenario gives rise to specific predictions about the ecological circumstances in which cheating can arise without driving the obligate mutual relationship to extinction, and it makes specific predictions about the Florida pollinator and how it interacts with its yucca host. We will first present the emerging scenario from available data, and then discuss how three specific predictions about moth phylogeography, moth phenology, and moth behavior and performance on yucca hosts will be tested (largely at Archbold) to test this scenario. FRIDAY, JANUARY 12 Morning Session "Biological soil crusts and their interactions with vascular plants in a xeric Florida shrubland." Christine V. Hawkes, University of California at Berkeley, Dept. ESPM, 151 Hilgard Hall, Berkeley, CA 94720 Biological soil crusts, consisting of algae, cyanobacteria, lichens, mosses, fungi, and bacteria, can aggregate soil particles and alter soil nutrients and moisture. They may also affect vascular plants, with consequences for population distributions and community composition. I studied soil crusts and their interactions with four endangered herbs in rosemary scrubs at Archbold. Observations along a chronosequence of disturbance by fire and experiments manipulating crusts were used to understand the distribution of crusts, the effects of crusts on seed germination, and the role of crusts in nitrogen cycling. Microalgae, cyanobacteria, diatoms, and chlorophyll a in crusts were heterogeneous in both space and time, and were generally most abundant 10-15 years postfire and away from shrubs. Crusts affected germination of three species, Eryngium cuneifolium (Apiaceae), Hypericum cumulicola (Hypericaceae), and Paronychia chartacea (Caryophyllaceae), but the effect was variable and lower in magnitude than other factors. More germination occurred in recently burned sites and away from shrubs. Germination of a fourth species, Polygonella basiramia (Polygonaceae), was unaffected by crusts or by site factors. Overall rates of germination were low, however, and may have been driven by rainfall. Delta15N natural abundances suggested that arbuscular mycorrhizal plants obtain nitrogen primarily from crusts whereas non-mycorrhizal herbs use nitrogen from deeper soils or precipitation. Addition of 15N as a tracer indicated that crusts have more than one function in scrub nitrogen dynamics: they fix nitrogen, compete with plants for nitrogen in rainfall, and retain leachable nitrogen in the system that becomes available to plants at a later time. Soil crusts are clearly an important component of the scrub ecosystem and may be in part responsible for the landscape we observe. "The genetic architecture of lichen symbioses in Florida scrub: population, metapopulation or community-level interactions?" Rebecca Yahr, Duke University Dept. of Biology, Box 90338, Durham, NC 27708, and P.T. DePriest, Smithsonian Institution, National Museum of Natural History, Washington, DC 20560 Species are sifted through stochastic and historic (evolutionary) screens of variable scale over evolutionary time to the produce patterns of distribution we observe today. The retrospective view offered by phylogenetic tools can offer insights into historical processes like evolution of life-history traits, biogeographic patterns, and coevolution. The lichen community of Florida's rosemary scrub is a consistent assemblage dominated by 6-7 terrestrial Cladonia species common to most or all scrub patches, although their algal symbionts are unknown. Dynamics of these communities may be dependant upon dispersability and reproductive mode of symbionts, by specificity among interacting partners, and by spatial structure of communities. We will present a preliminary view of these three factors in determining the dynamics and structure of Florida scrub lichen communities based on collections from north and central Florida scrub populations. "Nematode communities in Florida pastures." Robert McSorley, Dept. of Entomology and Nematology, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611-0620 Since nematodes are important constituents of most terrestrial and aquatic communities, they may be useful as bioindicators of disturbances and nontarget effects in many systems. Florida pastures, like most habitats, contain a wide variety of nematodes. The more than 50 genera found in soils of pastures in south-central Florida include bacterivores, fungivores, and herbivores, and to a lesser extent, omnivores and predators. The plant species present has a major effect on nematode community structure, as illustrated by differences from adjacent pasture and citrus sites. Within pasture sites, population densities of many nematode genera showed seasonal trends that were correlated with rainfall. In a short-term grazing experiment involving several different cattle densities. Monhystera, a bacterivore, was most consistently affected by cattle density. However, most nematode genera were unaffected by grazing, instead showing strong seasonal trends in population levels, with greater abundance in autumn than in spring, possibly due to increased rainfall and root production following the growing season. Additional research is needed to evaluate the relative importance of factors influencing nematode community structure."Disease factors in Hypericum edisonianum (Edison's St. John's Wort)." G. A. van de Kerckhove, University of Florida, Gainesville, FL 32611 Hypericum edisonianum, Edison's St. John's Wort, is an endemic, endangered shrub found growing in discrete populations in seasonal ponds in only four counties in Florida. Entire populations of this clonal plant have been observed to decline in a number of ponds throughout the Archbold property without there being any known disease etiology. The first objective of this study was to determine if in fact disease was present in H. edisonianum populations. Sphaeropsis tumefaciens (Sphaeropsis knot), an opportunistic fungal pathogen once common in citrus, has been newly recorded as infecting a number of H. edisonianum stands. The second objective was then to determine the vulnerability of H. edisonianum to both disease and severe environmental conditions. Although a great deal of genetic variability was discovered for this clonal species using AFLP (Amplified Frament Length Polymorphism) analysis, the plant is still subject to broad host-range pathogens. Drought and soil nutrient conditions appear to have synergistic affects with S. tumefaciens infection, which led to 85% mortality in one study pond in July 2000."Comparison of ecophysiology and genetics in a rare and a widespread species of Hypericum." K.P. Hogan*, K. Kettenring†, and G. van de Kerckhove*. *University of Florida, Gainesville, FL, †University of Minnesota, St. Paul, MN The physiology of plants is adapted to the conditions of the physical environment in which the plants grow. While this is obvious enough, it is unclear to what extent adaptations to environmental factors impose limits on the distributions of species, whether on geographical or local scales. Hypothetically, we can expect that plants with more limited distributions might be limited by a lack of genetic variation underlying the physiological responses to environmental factors. Thus in our comparative study of the local endemic Hypericum edisonianum and the more widespread Hypericum reductum, our working hypothesis is that H. edisonianum will show less genetic variation and a narrower range of physiological tolerances along environmental gradients. The high degree of environmental variation over very short distances at Archbold Biological Station make this an ideal site for the study of ecophysiological adaptations and their genetic basis. Our preliminary results are contrary to expectation, in that the widespread H. reductum shows more narrow ecophysiological tolerances than the local endemic H. edisonianum. Genetic analyses are still in progress, and show that H. edisonianum populations comprise much more genetic variation than we expected. A long-term objective of this research is to address the conflicting evolutionary forces of selection for local adaptation and ecotypic differentiation on one hand, vs. the maintenance of species integrity due to the homogenizing effect of gene flow through seed or pollen dispersal on the other. POSTER ABSTRACTS -- LISTED IN ALPHABETICAL ORDER BY FIRST AUTHOR "Patterns of acorn production for five oak species in xeric Florida uplands." Warren G. Abrahamson, Bucknell University, Lewisburg, PA 17837, and James N. Layne, Archbold Biological Station The number of fruits produced by a population of woody plants can vary markedly from year-to-year. Unfortunately, knowledge of the patterns and causes of crop-size variation is limited and most studies examine only single species in single mesic associations. We conducted counts of acorns annually 1969-1996 (except 1991) on two white oak species (Quercus chapmanii, Q. geminata) and three red oak species (Q. inopina, Q. laevis, Q. myrtifolia) across xeric sandhill, sand pine scrub, and scrubby flatwoods associations in south-central Florida. Although white oak species exhibited more frequent peaks in acorn production than red oaks, there was no correlation of production levels for species within an oak section or with temperature or precipitation. Consequently, acorns were produced with reasonable abundance every year by at least one species. Oaks in sand pine scrub with a well-developed pine canopy produced fewer acorns than similar-sized oaks of the same species in the more open sandhill and scrubby flatwoods. Following a prescribed sandhill burn, re-sprouted white oaks produced acorns more quickly than red oaks. White oaks produced acorns during the first year following fire whereas red oaks required 3 or 4 yr. to produce acorns. The percentage of bearing individuals and the mean number of acorns/bearing individual increased with increasing plant size for all species across associations. However, in some species in some or all associations, acorn production declined in the largest size class (>3m). "Influence of cattle ranching on nutrient loads and organic matter storage in wetland sediments." Patrick J. Bohlen, Archbold Biological Station, Don Graetz, University of Florida, Gainesville, FL, and Al Steinman, South Florida Water Management District, West Palm Beach, FL Many wetland ecosystems are exposed to grazing livestock but few studies have addressed interactions between cattle ranching and nutrient dynamics in wetlands. We are examining the influence of cattle ranching on nitrogen and phosphorus cycling, productivity, and organic matter storage and quality in seasonal wetlands of subtropical rangelands of south-central Florida. The experiment involves large-scale pastures with replicates of four different cattle stocking densities (control, low medium and high) in two different land use types: improved pasture and semi-native range. Phosphorus concentrations in wetland sediments were greater in improved pastures than semi-native pastures. Wetland sediment N:P ratios and C:P ratios were lower in the semi-native areas and fell within the range of values for the Everglades Water Conservation Area’s nutrient impacted and reference sites, suggesting a broad regional relevance for those values. Carbon storage was greater and C mineralization rates lower in sediments from wetlands semi-native pastures than in those from improved pastures. These results indicate that land use changes associated with beef cattle ranching alter nutrient concentrations and the quality of organic matter in wetland sediments and may alter the capacity of these systems to act as sinks for nutrients and organic matter. "Factors influencing variation in fledgling productivity in Red-cockaded Woodpeckers (Picoides borealis)." Reed Bowman*, David L. Leonard†, Diana Swan‡, and Donelle Schwalm*. *Archbold Biological Station, †Dept. of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, and ‡Florida Fish and Wildlife Conservation Commission, Gainesville, FL Demographic variation both within and between populations has important implications for the long-term persistence of populations and species. This is especially true for endangered species with populations demographically isolated from one another by habitat loss. We studied the demography of a relatively small, isolated Red-cockaded Woodpecker population for the last seven years at Avon Park Air Force Range. Here, nest success and fledgling productivity are lower than reported for any other RCW population. In this cooperative breeding species, experience and the presence of helpers influence fecundity, but the proportion of groups with experienced breeders and/or helpers is similar to other populations. Although nest success is low, nest predation rates (loss of entire nest contents) is not higher than in other populations. Hatching failure (defined as eggs that survive the incubation period but fail to hatch) rates are very high in this population; nearly 40% of all eggs laid fail to hatch. The cause of high hatching failure rates in this population are not known. The average age and dbh of cavity trees in this population is small, suggesting that cavity size may limit the ability of birds to effectively incubate their eggs. However, the proportion of whole clutch hatch failure did not increase with clutch size nor was hatch failure associated with the dbh of the cavity tree. In some species, hatching failure rates increase with the amount of social interactions among individuals. In our population, the age of first reproduction is high because adult survival is high. Many non-breeding males become floaters, which may increase the rate of social interactions. Hatching failure also may be a manifestation of inbreeding depression; however Fst values for RCW populations in peninsular Florida, including APAFR, are lower than elsewhere, suggesting more rather than less movement among populations. "Bottom-up effects on urban Florida Scrub-Jays: is too little or too much food a bad thing?" Reed Bowman*, Glen E. Woolfenden*, Matt Shawkey*,†, and Sonja LeClair*. *Archbold Biological Station, †Dept. of Biology, University of South Florida, Tampa, FL 33620 An active area of theoretical and empirical interest in ecology is the relative importance of top-down (predators and parasites) versus bottom-up (food or productivity) influences on the regulation of populations. Because the principle determinant of avian reproductive success is the rate of nest failure, most research has focused on the effects of nest predation or brood parasites such as the Brown-headed Cowbird. The process of urbanization, which dramatically alters community structure and composition, is likely to have profound effects on the natural foods available to species affected by urbanization. However, anthropogenic sources of food may be exploited by these same species. We have studied the demography and ecology of Florida Scrub-Jays (Aphelocoma coerulescens) in natural and suburban environments for over 10 years. Nest success and rates of nest predation do not differ between our scrub-jay populations; however, arthropods are less abundant in suburban scrubs than in natural scrubs. As a result, suburban Florida Scrub-Jays make fewer trips and deliver less food to nestlings. As a consequence, within-brood size asymmetries are greater, brood reduction is higher, and fledgling production lower than in the jay population at Archbold. Experimental provisioning of protein to nestlings decreases brood reduction and increases post-fledging survival, suggesting that diet may be limiting productivity. However, Florida Scrub-Jays readily use anthropogenic sources of food, such as bird feeders, peanuts, and pet foods. Access to supplemental food results in earlier laying dates and decreased between-year variation in laying date. Although earlier breeders usually fare better than birds breeding late in the season, suburban scrub-jays did poorest relative to scrub-jays in natural habitats, when the difference in laying date was greatest. Scrub-jays in natural scrub may vary laying date to coincide with seasonal resources. If Florida Scrub-Jays use supplemental food as a cue to initiate breeding, but nest before seasonal resources are available, then supplemental food, rather than mitigating the loss of natural food, may further reduce its availability. Our results suggest that bottom-up rather than top-down influences are important in regulating suburban populations of Florida Scrub-Jays. "Mass loss in breeding Florida Scrub-Jays." Kimberly Boots Brand, Dept. of Biology, University of South Florida, Tampa, FL 33620 Loss of body mass in breeding birds has been explained by four not mutually exclusive hypotheses: reproductive stress, flight adaptation, energy-reserve mobilization, and gonadal regression. In 1999 and 2000, Florida Scrub-Jay breeders were trained to land on an electronic balance and were measured repeatedly during all stages of the breeding cycle, from prelaying to fledgling independence. During early incubation, females were significantly heavier than they had been during prenesting. Mass loss in female breeders occurred during incubation and the nestling stages and was mostly complete by fledging, before peak effort for females as determined by food delivery rate and foraging rate. Mass loss before peak effort suggests support for either the flight adaptation or energy-reserve mobilization hypotheses. Also consistent with these two hypotheses, females returned to their prenesting mass, and females whose nests failed during the nestling stages exhibited the same pattern of mass loss as females whose nests succeeded. Thus, mass loss in female Scrub-Jays appears to be a regular part of the breeding cycle, not the result of reproductive stress. The pattern of mass loss for male breeders was similar to that of female breeders, though the extent of mass loss was much less. For males, peak effort begins earlier in the breeding cycle, during the nestling and early fledgling stages when males forage at the greatest rate and feed young at a significantly greater rate than do females. Because mass loss coincides with peak effort, it is likely that mass loss in male breeders is best explained by reproductive stress. Also consistent with reproductive stress, male breeders whose nests failed during the nestling stage rapidly gained mass. "Vegetation structure and post-fledging survival of Florida Scrub-Jays in suburban and natural habitats." Michelle L. Dent and Reed Bowman, Archbold Biological Station Over 30% of all Florida Scrub-Jays live in a suburban matrix and these populations appear to be declining. Annual recruitment is lower in these suburban populations for which higher than average post-fledging mortality has been implicated. We compared the post-fledging survival of young scrub-jays and the characteristics of habitats used during the post-fledging period in both suburban and natural scrub. During 1998, we monitored fledgling scrub-jays every 2-6 days to determine temporal patterns of post-fledging survival and vegetation use. Post–fledging survival to nutritional independence (~85 days post-hatch) differed between sites (72.7% natural scrub vs. 51.6% suburban scrub). At both sites most mortality occurred within 22 days post-fledging (83.3% of all deaths, natural scrub; 71% of all deaths, suburban scrub); however, the overall mortality rate during this period was higher in the suburbs than in the natural scrub (34.4% vs. 22.7%). From then until independence, mortality rates decreased. At both sites, fledglings predominately used native habitats; however, the characteristics of these habitats and their use differed. In the suburban habitat, smaller territory size limited fledgling movement away from the nest. In both habitats, scrub oaks predominated, but the composition of oak species differed. Suburban scrub was more open than natural scrub (mean distance to nearest cover was 1.2 m vs. 0.3m). Although the combined shrub and tree density was lower in the suburbs (0.11 stems/m vs. 0.25 stems/m), the combined shrub and tree height was taller (mean height was 1.67 m vs. 1.04 m). At both sites, fledglings depart the immediate vicinity of the nest, but in the suburbs fledglings must cross more and larger areas with little or no cover, potentially exposing them to a variety of hazards (humans and vehicles) and predators (i.e. cats, raccoons, snakes, avian predators). "Discovering Florida Scrub; a guide to exploring science in a native ecosystem." Nancy Deyrup, Archbold Biological Station This new curriculum for 3-5th grades was developed by Nancy Deyrup and Charlotte Wilson of the Archbold Biological Station with funding from a grant from the Florida Fish and Wildlife Conservation Commission’s Advisory Council on Environmental Education. The goal of this curriculum is to give teachers and students a deeper understanding of science and the practice of science, and a greater appreciation for the Florida scrub, a critically endangered ecosystem. Discovering Florida Scrub provides teachers with background information, objectives, Sunshine State Standards, glossary, and student evaluation questions for the indoor and outside the classroom hands-on, inquiry-based student activities. The four units feature plants and animals easily found in the Florida scrub habitat. However, it is important to remember that the concepts behind these activities apply to other Florida ecosystems. Unit One investigates sand, exploring the physical properties of sand and the animal signs found there. Unit Two features sand dwelling animals, particularly ant lions, scrub burrowing wolf spiders, and ants. Unit Three reveals life in the leaf litter layer by looking at mushrooms, decomposers, and microhabitats. Unit Four focuses on plant-animal interactions. "Responses of functional groups to pulsed resources." Dave Evans*, John Dighton†, James Carrel‡, Eric S. Menges‡§, Patrick J. Bohlen‡§, and Hilary M. Swain‡§. *University of Arkansas, Fayetteville, AR, †Rutgers University, New Brunswick, NJ, ‡University of Missouri, Columbia, MO, and ‡§Archbold Biological Station Critical resources in ecological systems are often episodically available in pulses of varying magnitude and duration. Because of complex interactions and feedbacks, it is difficult to understand responses to pulsed resources in one part of the system in isolation. In this proposal, we consider a linked sequence of processes in key functional groups: (1) pulses of plant available nutrients (chiefly N, P, K) are created by rainfall events, seasonal precipitation and fire; (2) key ecosystem components, such as soil crusts and decomposers, will release and modify nutrients, creating secondary pulses and spatial heterogeneity; (3) water and nutrients are taken up by different functional groups of shrubs and herbs associated with their specific mycorrhizal symbionts. We expect differentially quick responses among functional groups to pulses of various frequencies and durations. We outline here our proposal to test predictions concerning the nature and magnitude of pulses of plant available nutrients in the FL scrub ecosystem, in response to (1) rainfall events (2) seasonal precipitation and (3) fire in (a) soil crusts (b) decomposers and (c) soils, and the subsequent differential uptake of these plant available nutrients by mycorrhizal symbionts/roots of 3 functional groups of shrubs and herbs (resprouting shrubs, resprouting herbs, and reseeding herbs). This proposal is under development to be sent to potential funding agencies and we welcome feedback and comments. "Reactions of Florida Scrub-Jays (Aphelocoma coerulescens) to eggs and shams added to their nests." Tina L. Fleischer, Archbold Biological Station, and Dept. of Biology, University of South Florida, Tampa, FL 33620 Avian brood parasites, such as the Brown-headed Cowbird (Molothrus ater), Shiny Cowbird (M. bonariensis), and Bronzed Cowbird (M. aeneus), lay their eggs in the nests of a large number of other species. Some of these species reject cowbird eggs, many accept them, and accepters experience decreased reproductive success. Since the time of European settlement of North America, Florida Scrub-Jays (FSJs) have not lived where brood parasites breed. However, in the last few decades Brown-headed Cowbirds and, to a lesser extent Shiny Cowbirds, have invaded the range of the FSJ in central Florida. At present, no evidence exists for parasitism of FSJs by cowbirds. However, if FSJs were to raise cowbirds, yet another threat would be added to the problems facing this rapidly declining endangered species. This study tests the reactions of the FSJ to experimental introductions of cowbird eggs, the eggs of a few other species, the eggs of conspecifics, and shams. Among the questions I sought to answer were: 1) Do FSJs reject cowbird eggs? 2) If they do reject eggs, can they discriminate between their own eggs and the eggs of conspecifics? Most shams (17 of 23; 73.9%) were rejected, including all 6 FSJ shams. Most cowbird eggs (14 of 20; 70.0%) and other non-scrub-jay eggs (21 of 24; 87.5%) added to nests were rejected. Shams and non-scrub-jay eggs were rejected most often within 1 day of addition. Some of the FSJ eggs (6 of 30; 20.0%) were rejected. No FSJ rejected its own egg by mistake. FSJ eggs were rejected from the day of addition up to 15 days after addition. Ejection of cowbird eggs by FSJs suggests that cowbirds pose little threat to their persistence. Some fossil evidence suggests that ancestral FSJs may have been sympatric with Brown-headed Cowbirds during the Pleistocene and evolved the ability to reject in response to brood parasitism. "It’s a spider-eat-spider world: does the risk of predation shape Archbold’s wolf spider community?" M.A. Hodge, Department of Biology, The College of Wooster, Wooster, OH 44691 Intraguild predation (IGP) refers to predatory interactions between different species which use similar resources. Because most spiders are generalist predators on arthropods, different species may interact as both competitors and predators, making them model organisms for the investigation of intraguild predation. The goal of this study was to examine the potential for IGP interactions between two species of Hogna sympatric in scrub habitats at Archbold Biological Station: H. osceola (the larger species) and H. ceratiola. These two species represent over 80% of the nocturnal wolf spider fauna. Since hunger is a factor affecting the liklihood of IGP, a measure of food limitation was obtained for each species. Laboratory measures found that spiders are not near satiation, and only 8-10% of spiders collected on a given evening had prey, indicating that food is available in a limited supply. Spiders are capturing prey that are smaller than themselves, even when these prey are other spiders. Between 8% (H. ceratiola) and 21% (H. osceola) of the diet of each species consists of other spiders. Between 50% (H. ceratiola) and 100% (H. osceola) of the spider prey taken represented cannibalism or IGP on the other species. Discriminant analysis of habitat use by the two species found that H. osceola tends to forage in vegetation, whereas H. ceratiola tends to forage on open sand. The two species overlap, however, in their use of leaf litter. Since leaf litter was found to have more insect prey than open sand, I designed field enclosure experiments to examine the role of interspecific interaction on ground substrate preference by the two species. When alone in enclosures, H. osceola preferred leaf litter and H. ceratiola showed no distinct preference for either substrate. When both species shared the enclosure, H. osceola retained their preference for leaf litter while L. ceratiola exhibited a distinct preference for sand. In addition, H. ceratiola gained significantly less weight when with H. osceola than they did when in enclosures by themselves, indicating a potential interference effect of H. osceola. These results suggest that habitat use by H. ceratiola may be mediated by IGP interactions with H. osceola. "Controls on nutrient runoff from cattle ranches in the Lake Okeechobee Basin." Greg Huey*, Lourdes Rojas*, Patrick Bohlen*, John Capece†, Ed Rawlinson†, and Ken Campbell‡. *Archbold Biological Station, †Southern DataStream, LaBelle, FL, and ‡University of Florida, Gainesville, FL In 1994, Archbold Biological Station initiated a long-term project with the University of Florida, South Florida Water Management District, and the Florida Cattlemen’s Association to demonstrate the influence of different beef cattle management practices on water quality in south Florida. A major goal of the project is to aid in developing Best Management Practices (BMPs) that will help reduce phosphorous loads in surface runoff into Lake Okeechobee while maintaining the economic viability of Florida cattle ranches. The experiment consists of 16 field-scale plots that are separately fenced, ditched and instrumented so that all surface water runoff can be quantified, sampled and analyzed. The 16 plots include 8 semi-native pastures which are grazed November-April and 8 improved pastures which are grazed May-October. The initial experiment examines the effect of four different cattle stocking densities on water quality. Stocking rates are 0, 1.4, 2.5, and 3.3 acres/cow-calf unit on improved pastures and 0, 2.3, 4.0, and 5.3 acres/cow-calf unit on semi-native range. The cattle stocking rate treatments were started in autumn 1998. The improved pastures show much greater total phosphorous concentrations and loads as compared to the semi-native pastures, possibly due to prior land use. Total P loads in 1998 and 1998 were 0.11 and 0.15 kg/ha in semi-native pastures and 0.73 and 0.82 in improved pastures. Ammonia concentrations were greater in runoff from improved pasture than from semi-native pastures in both years. In 1999 loads of ammonia and total Kjeldahl nitrogen were greater from improved pasture than from semi-native range. Cattle stocking density has not yet had any significant effect on nutrient concentration or loads in surface runoff. "Endangered, Threatened, or Rare Species of the Lake Wales Ridge, Central Florida: A Web reference for regional biota http://www.archbold-station.org/fai/species4.html." Fred E. Lohrer and Hilary M. Swain, Archbold Biological Station The Lake Wales Ridge is Florida’s oldest terrestrial land form and it harbors many endemic plants and animals. Much attention is focused on this regional biota because of conservation issues, yet this biota is often poorly represented in major field guides. This Web reference-page is a gateway to Internet information, especially images, for those unfamiliar with this biota (including regional land managers and government personnel, students, the general public, and even many biologists). This is an evolving document and we are eager to modify and improve this Web reference based on user comments. We hope this Web reference will encourage others to develop similar products for other regions of critical conservation-education focus. "Gapology in Florida scrub: integrating spatial and demographic approaches." Satya K. Maliakal*,†, Martina Petru*,‡, Owen D. Boyle*,‡§, and Eric S. Menges*. *Archbold Biological Station, †Louisiana State University, Baton Rouge, LA, ‡University of South Bohemia, Czech Republic, and ‡§University of Wisconsin, Madison, WI Gapology is our attempt to integrate spatially-explicit data on gaps with the demography of many scrub plants. We define gaps as openings among dominant shrubs (e.g. oaks, rosemary) that may have bare sand, lichens, herbs, or shrub stems less than 50 cm tall. Gaps are important microhabitats for myriad Florida scrub plants. We are locating and measuring thousands of gaps using GPS and ground measurements. In about five years, we will re-census these gaps, and derive estimates of gap demography such as "death" of small gaps, shrinkage in gap size, and coalescence and creation of gaps after fires. A number of demographic projects are utilizing this common gapology framework. Maliakal’s thesis is comparing the importance of gap size on the demography of two Florida scrub endemics primarily restricted to gaps in rosemary scrub (Polygonella basiramia and Lechea cernua) with the demography of two widespread, less specialized congeners. Petru is examining the effects of experimental aboveground vs. belowground gaps on seedling recruitment, in rosemary scrub and scrubby flatwoods, as part of her master’s research. Using both gap and habitat patch scales, Boyle will develop a spatially explicit metapopulation model for P. basiramia, including measuring subpopulation growth, extinction, and colonization rates, genetic structure, spatial structure, patterns of gene flow, dispersal, and habitat patch quality. Many plant lab projects will become spatially-explicit through gapology. For example, we will be examining source-sink dynamics in a population of Dicerandra christmanii, part of which is slated for an experimental burn. Fire-induced temporal and spatial shifts in genetic structure of Hypericum cumulicola will be tracked in a burn unit in which all xeric gaps have been mapped and measured. Our gapology approach will integrate spatial and demographic data, population and landscape scales, and independent research projects, increasing our understanding of the ecology of Florida scrub."Evaluating population viability with fire in Eryngium cuneifolium: deciphering a decade of demographic data." Eric S. Menges and Pedro F. Quintana-Ascencio, Archbold Biological Station We model demography of Eryngium cuneifolium, a Florida scrub endemic. Using 10 annual censuses (1990-1999) of 11 populations at Archbold Biological Station, we built 54 matrices representing different time-since-fire. Twelve fecundity and seed bank scenarios were evaluated based on available data. The stochastic simulation program DISTPROJ was used to obtain estimates of extinction probability under different regular fire intervals. The scenario with high seed bank survival (0.5) and low germination rates (0-0.4) was the best predictor of observed years of peak plant number (8) and aboveground disappearance (30-34). Time-since fire had major effects on demography. For example, survival of seedling cohorts recruiting shortly after fire was greater than for later cohorts. Finite rates of increase were > 1 only during the first decade postfire, and decreased with time-since-fire. Elasticities for survival increased with time-since-fire, while other elasticities decreased. Our results indicated that frequent fires with return intervals of 15 years or less are necessary for E. cuneifolium persistence. Since rosemary scrub may burn less often, local extinctions and metapopulation dynamics may be the norm for this species. Other rosemary scrub specialists (e.g. Hypericum cumulicola) thrive with less frequent fires. Therefore, we suggest that variation in fire regimes will allow co-existence and hedge against local extinctions. "Current demographic research in Archbold Biological Station's Plant Ecology Lab." Eric S. Menges*, Carl Weekley*, Pedro F. Quintana-Ascencio*, Alaä L. Wally*, Dorothy E. Mundell*, Christine V. Hawkes*,†, and Samara Hamzé*. *Archbold Biological Station, and †University of California at Berkeley, Berkeley, CA We are currently studying the demography of 22 plant species occurring in Florida scrub. These studies go back as far as 1988. We sample multiple sites (dozens in several cases) and hundreds or thousands of marked plants at annual, quarterly, or more frequent intervals. Population dynamics is a common theme, but more specialized topics include metapopulation dynamics, microhabitat specialization, seed biology, herbivory effects, pollination biology, genetics, and competition. Multiple studies allow comparisons of life histories and demographic properties, such as life span, mortality rates, and individual postfire responses. We are examining postfire demographic responses to assess the effects of alternative fire management strategies (e.g. fire return intervals, variation in fire intensity) on population persistence. A population viability analysis for Hypericum cumulicola has demonstrated that fires every 50 years or less are necessary to avoid local extinctions. Several other PVAs are underway. Seed dormancy and seedling dynamics are the focus of studies on the annual herb Warea carteri, where population increases postfire are consistent with increased germination in surface microsites without litter, typical shortly after fire. We are employing population modeling to assess the effects of seed harvests for ex situ conservation. More frequent, lighter harvests typically created lower extinction risks than less frequent, more-intensive harvests. A recent PhD thesis examined the effects of microbiotic soil crusts on seedling recruitment of scrub plants. Crust effects were variable and complex, and crusts have important effects on nitrogen dynamics in the oligotrophic scrub soils. "Effects of small-scale disturbances on the regeneration of Florida scrub plants." Martina Petru, University of South Bohemia, Czech Republic, and Archbold Biological Station Disturbances create opportunities for seedling recruitment and population expansion in many ecosystems. In Florida scrub, fire creates large gaps. However, small-scale disturbances such as animal trails, animal mounds, and sand movements have not been well studied. In this poster, I describe a series of interlocking experiments exploring seedling recruitment in artificial gaps of different types as well as in natural gaps of different sizes and types. For an experiment in rosemary scrub and scrubby flatwoods, I created artificial aboveground gaps by clipping vegetation, and artificial belowground gaps by removing all shrub roots and rhizomes. In both artificial and natural gaps, I am monitoring spontaneous recruitment and recruitment from sown seeds of six scrub species. I have also been recording abiotic conditions in gaps and watering some gaps during this drought period. In a lab experiment, the effects of rainfall of different frequencies on seed germination, seedling recruitment and survival is being tested. The effects of sand movements are examined in lab and field experiments on seeds and established plants, respectively. I calibrated sand movement levels for experiments from observations in scrub and along roads and trails. I am also examining small-scale disturbances created by animal trails for their effects on seedling recruitment. This network of experiments will elucidate the mechanisms by which gaps provide critical microhabitats for many endemic Florida scrub plants. "Developing methods for measuring fire intensity: insights from a mow and burn experiment."Alaä L. Wally, Carl Weekley, and Eric S. Menges, Archbold Biological Station Fire is essential to many ecosystems worldwide, but fire effects may vary greatly with small-scale variations in fire intensity. More intense fires are characterized by higher maximum temperatures and longer residence times. The various methods to estimate fire intensity are not always congruent. Dataloggers are capable of reliably collecting precise, detailed information on fire temperature and duration, but they can only be deployed in a limited area due to their expense and difficulty of installation. Pyrometers (metal tags with paints that melt at given temperatures) and calorimeters (aluminum cans with water that evaporates) are cheaper and more efficient but less precise. In June 1999, we deployed dataloggers, pyrometers, and calorimeters in several areas of a mow/burn experiment at Lake Apthorpe Scrub. A combination of pyrometer and calorimeter data explained a large proportion of variation in thermocouple temperature data taken from the same locations. Pyrometer data was weakly correlated with maximum temperature whereas calorimeter data best reflected the number of minutes >150oC. Calorimeters and pyrometers were largely congruent in fire intensity ranking of fuel types and treatments. Pyrometers revealed greater burn heterogeneity in unmown scrub vs. mown scrub. Both calorimeters and pyrometers recorded higher maximum temperatures in scrub plots than in mown plots. These results emphasize the utility of measuring fire intensity over larger spatial scales than dataloggers allow. We plan further testing of thermocouples, pyrometers and calorimeters at Archbold Biological Station, Lake Placid Scrub, and Gould Road Scrub to determine the consistency of these results. "Saving Florida Ziziphus: restoration ecology of a rare Lake Wales Ridge endemic." Carl W. Weekley1, Thomas L. Kubisiak2, Tammera M. Race3, and Eric S.Menges1. 1Archbold Biological Station, 2US Forest Service, 3Bok Tower Gardens Florida ziziphus (Ziziphus celata Judd & D. Hall [Rhamnaceae]) is one of the most imperiled plants in North America. It comprises only five populations, four of which are sterile and probably uniclonal. Only eleven genotypes of Florida ziziphus have been identified by allozyme electrophoresis. To develop a recovery strategy for Florida ziziphus, we are studying its reproductive biology and genetics. We conducted breeding system experiments to test for agamospermy (ability to set viable seed without pollination), self-compatibility, agamospermy (spontaneous selfing), and within- and between-genotype compatibility. We used the Random Amplified Polymorphic DNA (RAPDs) technique to reassess the genetic variability of Florida ziziphus and to identify potentially cross-compatible genotypes. Eleven multi-locus genotypes were identified by RAPDs, eight of which correspond to allozyme genotypes. Coefficients of similarity ranged from 96.6% for the most closely related genotypes to 20.7% for the most distantly related. We found that Florida ziziphus is an obligate outcrosser and that some genotypes are also cross-incompatible. Eleven of 38 crosses conducted to date (29%) have yielded fruit. However, determination of cross-compatibility is complicated by the presence of parthenocarpic (seedless) fruits and by high levels of seed abortion. Thus, only five crosses have resulted in germinants. Cross-incompatibility is most likely due to shared self-incompatibility (S) alleles among the few remaining genotypes of these fragmented populations. The identification and translocation of compatible mating types to create reproductively viable populations is essential for the recovery of Florida ziziphus. An experimental introduction to a protected site containing appropriate habitat is planned. |
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Deyrup, M., Fleischer, T, and E. Menges, January 2001,
revised 9 January 2001.
© Archbold Biological Station, 8 January 2001.
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