Members of the Plant Ecology Lab in spring 1997: L-R; Pedro
Quintana-Ascencio, Michael Kelrick, Kurt Reinhart, Rebecca Yahr, Christina Casado, Eric
Menges, Satya Maliakal, Graham Walker, Dorothy Mundell; photo by Nancy
Deyrup
- Published 9
peer-reviewed papers and book chapters in such journals as Conservation Biology,
Journal of Ecology, Ecological Applications, and American Journal of
Botany.
- Worked under 8 extramural
grants involving demography, genetics, fire management, and conservation of Florida
scrub plants.
- Awarded a 5-year grant from National Science Foundation to
continue data collection and population viability analyses on Florida scrub plants.
- Continued collection of long-term demographic data on
Florida scrub plants, now in the 11th year for 3 species.
- Facilitated many research projects, including 5 Ph.D.
projects from 5 universities.
A conceptual model for vegetation
dynamics in an upland Florida landscape. Arrows indicate hypothesized
transitions under various disturbance regimes: FF = frequent fires (1–10
yr), MF = moderately frequent fires (5–20 yr), IF = infrequent fires
(15–100 yr), NF = no fires within 100 yr, WF = winter fires, PR =
pine removal, F = fire reintroduction (Ecol. Appl. 8:935–946, 1998).
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Plant Ecology Research &
Plant Ecology: New Approaches and New Species
Project Director: Eric S. Menges
Research Assistants (Full Time): Christina M. Casado, Carl W. Weekley, Rebecca Yahr
Research Assistants (Part Time): Michael N. Gushee, Christine V. Hawkes, Richard J.
Lavoy, Dorothy E. Mundell, William R. Smith, Donald M. Stillwaugh Jr., Helen A. Violi,
Diane Willis
Graduate Intern: Pedro F. Quintana-Ascencio
Undergraduate Interns: Matthew S. Finer, Erica M. Goss, Phillip E. Higuera, Molly
E. Hunter, Satya K. Maliakal, Abigail L. McCarthy, Patrick J. McIntyre, Kurt O. Reinhart
Volunteers: Dorothy E. Mundell, Graham Walker; Partners for Plants
volunteers--Vickie Denton, Helen Goodhue, Frances Hufty, Sally Robinson, Mary Frances
Wagley, Robbie Wurts
Outside Collaborators: Dawn M. Berry, Florida Game and Fresh Water Fish Commission;
Rebecca W. Dolan, Butler University; Margaret E.K. Evans, University of Arizona; Daniel
Gagnon, University of Quebec at Montreal; Doria R. Gordon, The Nature Conservancy; Michael
L. Kelrick, Truman State University; Peter L. Marks, Cornell University; Pedro F.
Quintana-Ascencio, ECOSUR, Mexico; Tammera Race, Bok Tower Gardens; Richard B. Root,
Cornell University; Joan L. Walker, Clemson University; Rebecca Yahr, Duke University
Visiting Researchers: Christine V. Hawkes, University of Pennsylvania; Olle
Pellmyr, Vanderbilt University; Sonja Scheffer U.S. Department of Agriculture; Gayle vande
Kerckhove, University of Florida
[ Biennial Contents
| Biennial 95-96 | Research ]
Highlights of plant ecology research
during 1997-98 include the conclusion of several important projects (a major, integrative
rangewide study of genetic variation in seven Florida scrub endemic plant species; the
first population viability analysis for a scrub plant), integrative summaries (two reviews
of scrub ecology, a review of population viability analysis in plants), complementary
projects on the life history of several scrub plants, and the initiation of projects on
new species and new management strategies (see below).
Long-term funding was secured from the National Science Foundation to build, analyze,
model, and expand decade-long databases on the demography of scrub plants.
Genetic
Patterns in Scrub Plants. A multi-year study on the genetics, ecology, and preserve
design of seven Florida scrub endemic plants continued in 1997–98, with one of the
highlights being an 11-chapter report to The Nature Conservancy (see Doria Gordon, which helped fund the project. This study
combined detailed experiments on life history with a rangewide survey of genetic variation
(see maps, page 11 and page 29 [d] ). The species were found to be dependent upon
pollinators, but five of seven can produce seeds from within-plant pollinations. Gene flow
via pollinators varies but that due to seed dispersal is very limited. Isozyme (genetic)
variation is rather low, but varies widely across species. Within species, larger
populations in larger soil patches have more genetic variation for three species, but
results vary depending on the measure of genetic variation. Comparing species, long-lived
outcrossing species with stable demography and strong pollen flow had greater genetic
variation. Genetic data were used to identify populations that are especially significant
for conservation. The good news is that the proposed reserve system protects over 85% of
polymorphic alleles detected by the study.
Standing out among the seven species was Hypericum
cumulicola, which contains an extraordinary proportion of its limited genetic
variation among (rather than within) populations. Genetic differences among populations
also occur at smaller scales, such as within Archbold. Genetic patterns of transplants,
native plants, and their offspring were used as evidence for limited gene flow and
metapopulation dynamics in a collaborative paper published in 1998 in Journal of
Ecology by Pedre Quintana-Ascencio, Rebecca Dolan, and Eric
Menges.
[ Quintana-Ascencio, P.F., R.W. Dolan, and E.S. Menges. 1998. Hypericum
cumulicola demography in unoccupied and occupied Florida scrub
patches with different time-since-fire. J. Ecol. 86:640-651. ]
Population Viability Analyses and Long-Term Research.
Population viability analyses (PVA) project the future of populations based on demographic
and other data, and are often used to evaluate alternative management strategies for
endangered species. In 1997, Quintana-Ascencio completed the first PVA for a Florida scrub
plant, using a modeling approach that incorporated stochastic variation in demographic
parameters and the fire/recovery cycle of Florida scrub. Populations of Hypericum
cumulicola are viable when frequently-burned but can often persist as dormant seed
banks for several decades after aboveground populations have perished between fires.
Menges conducted a literature review of plant PVAs for talks in Sweden and Italy, finding
that plant PVAs differed in important ways from PVAs constructed for animals, and finding
disturbing limitations in the duration of studies and in the numbers of populations
considered. He has been invited to write a review of plant PVAs for Trends in Ecology
and Evolution. Menges and Dolan also published a PVA for a midwestern prairie plant in
Journal of Ecology, finding that fire management was the most important factor in
ensuring population viability for this species.
Further PVAs are planned for scrub species with long-term
demographic data, ranging from perennial shrubs to an annual herb. The long-term datasets
collected on a number of scrub species, up to 11 years in length from multiple populations
(see Table 1), provide a rich source of data on temporal variation in demography which is
key for PVAs. The National Science Foundation’s Program, Long-Term Research in
Environmental Biology, has awarded funding for 5 years, beginning in 1999, for additional
data collection, population viability modeling, and explicit spatial analyses, both at
within-patch and landscape scales.
Integration of Scrub Ecology. The Plant Ecology Lab has
been the home of myriad projects conducted by staff, visiting scientists, and graduate
students during the last decade. Integration of these data provides efficient
communication of results and can stimulate new projects. Two integrative reviews were
published in 1998. Menges and Christine Hawkes reviewed the interactive role of
fire and microhabitat on Florida scrub plants in an article published in Ecological
Applications. They emphasized changes that occur at landscape scales, local patches,
and microsites. Alterations in fire regimes cause complex feedbacks at both scales and can
then alter future fire effects (see fig., page 10). A more general review of scrub biology
by Menges includes summaries of demographic and metapopulation research on a variety of
Florida scrub organisms.
Complementary Approaches: Dicerandra frutescens.
Another type of integrative science occurs when different studies on the same organism
combine to provide additional insights. This is illustrated by various projects on the
endangered scrub mint, Dicerandra frutescens. The long-term demographic work
suggests that fire-suppression is a threat to this species, and more recent publications
on its microhabitat show that structural habitat changes occurring between fires cause a
decline. Genetic analyses reveal extremely narrow variation, perhaps due to periodic
population crashes. However, little genetic difference exists among various populations,
suggesting that gene flow has connected these patches in the past. Pollination studies
recently published by Menges and Mark Deyrup suggest that pollination doesn’t
limit fruit production, but it may affect the fitness of subsequent seedlings. Outbreeding
depression, studied by intern Abigail McCarthy, has the potential to reduce the
fitness of seedlings resulting from long-distance crosses. While gene flow by pollen may
be substantial, intern Matthew Finer
showed that seed dispersal is rare much beyond the parental canopy. Consequently, loss of
dormant seed banks due to fire suppression could be very important to population
persistence. Recent experimental fires in long-unburned populations, combined with a
3-year field seed bank experiment conducted in collaboration with Michael Kelrick
(Truman State Univ.), will help evaluate the longevity and resilience of dormant seed
banks in D. frutescens.
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Partners for Plants volunteers,
including Frances Hufty of Archbold Expeditions (seated in the
vehicle) assemble at Carter Creek Preserve, April 1998, with Rebecca
Yahr (standing left) and Eric Menges (far right) of the Plant Ecology
Lab; photo by Eric Menges.
Eric Menges and Daniel Gagnon install a
soil moisture probe, photo by Nancy Deyrup.
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Plant Ecology: New Approaches and New Species
[ Top ]
Conservation Biology. Crises in
conservation and management need prompt attention from researchers in conservation
biology. During 1997–98, the Plant Ecology Lab initiated new projects to gather
important data on two critical species and on some alternative management strategies. With
help from Partners for Plants volunteers (see photo, this page), we initiated studies of Crotalaria
avonensis at its largest remaining site, the Carter Creek Preserve, managed by the
Florida Game and Fresh Water Fish Commission (FGFWFC). Initial data suggest that this
plant can thrive in a variety of microsites, but that limited fecundity, irregular growth
patterns, and herbivory may be factors that could affect its demography. Ongoing research
on the extremely endangered shrub, Ziziphus
celata, now part of the Plant Lab program, has been conducted by Carl Weekley
with the collaboration of Tammera Race (Bok Tower Gardens). Recent breeding systems
experiments show that only certain crosses among particular genotypes and populations
result in fruit and seed production. Such information is of practical use in planned
introductions of this species to new protected sites on the Lake Wales Ridge.
Alternatives to Fire
Management. Although fire management is widely viewed as necessary for management of
Florida scrub and adjacent vegetation in the Florida landscape, it is often difficult to
apply for logistical and political reasons. However, the effects of additional or
alternative management practices are poorly known. The Plant Lab started two studies to
examine mechanical treatments and pre-treatments and their effect on scrub communities.
Both involve close collaboration with stage agencies. At Lake Wales Ridge State Forest, we
are examining sand pine scrub response to logging and fire in cooperation with two state
agencies. Extensive before-treatment sampling has been concluded and treatments are slated
for 1999. Similarly, 1999 treatments following extensive before-treatment data from three
sites are the exciting next step in a project on mowing and fire conducted in
collaboration with the FGFWFC, and supported by a grant from the U.S. Fish and Wildlife
Service.
Differences between fire
treatments, with and without mechanical pretreatments may be due to differences in fire
intensity and its heterogeneity over space. We are planning comparative studies in fire
intensity and heterogeneity in South Carolina sandhill vegetation and Florida scrub
vegetation, in concert with Joan Walker (Clemson Univ.).
Water and Nutrient
Dynamics. While data from Archbold provide many interesting examples of spatial
patterning and habitat specialization among Florida scrub plants, the mechanisms for these
phenomena are poorly known. For example, it is widely viewed that plant communities may be
distributed in the landscape in response to water availability, nutrient levels, fire, or
combinations of these three. However, little work on water or nutrients has been done. In
1998 Daniel Gagnon has brought new technologies and
ideas to bear. Frequency domain reflectometry measures soil water outside 78 permanent
tubes in various locations at Archbold (see photo, this page). The role of crytobiotic
soil crusts in providing nitrogen to the low-nutrient scrub soils is one of the questions
in Christine Hawkes’ ongoing Ph.D. investigations.
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