Distribution: Wedgeleaf eryngium is endemic to the southern tip of the Lake Wales Ridge, found only in the southern half of Highlands County. It is federally and state listed as endangered with fewer than 20 known populations.

Habitats: Wedgeleaf eryngium is found only on xeric white sands in rosemary scrub and disturbed areas. Within rosemary scrub, the species is highly specialized for gaps among rosemary shrubs and for recently burned areas. The highest population densities are in disturbed and recently burned areas.

Life History: Wedgeleaf eryngium is a short-lived herbaceous perennial, with a basal rosette and flowering scapes. It possesses a deep taproot but rarely resprouts following fire. Perfect, small, greenish flowers (10-15) are borne on head-like umbels, the heads displayed on a diffusely branching inflorescence. The species has a persistent seed bank that is particularly apparent after disturbances, as subsequent seedling densities can be locally very high.

Phenology: Plants flower for about a month in late summer or fall, producing seeds in the fall. Germination occurs in the winter and spring. Although some seeds can germinate shortly after maturation, most seeds remain dormant for a year or more, germinating in subsequent winter seasons. After fruiting, reproductive stems soon wither and die. Basal rosettes may remain green overwinter or disappear briefly.

Breeding System and Pollination: Wedgeleaf eryngium has perfect, protandrous flowers displayed in head-like umbels. The umbels progress from male to female phases producing a temporal separation of gender function within umbels. However, because there may be hundreds of umbels on a plant, both male and female phase flowers are usually present on the same plant. The species is self compatible with a mixed mating system. The degree of selfing vs. outcrossing appears heterogeneous based on genetic data. Wedgeleaf eryngium requires insect pollinators to produce seeds. Autogamous pollination produced only 4% seed set. Many species (at least 100) of generalist insects are frequent (0.3 visits per minute) visitors and likely pollinators. Most insects are apparently seeking nectar although some collect pollen. Pollinator visitation does not appear to limit seed production, and open pollinated seed set was very high (80%). Most insect movements are among flowers on the same plant or between nearby (< 5 m apart) plants. Self and cross treatments produced similar numbers of seeds, suggesting that inbreeding depression is not acting at this life history stage.

Genetics: Based on isozyme studies, wedgeleaf eryngium has less genetic variation than expected for a narrowly endemic plant, but intermediate among three studied co-occurring Florida scrub endemic plants. For example, expected heterozygosity is 0.054, compared to 0.074 for endemics in general. Predicted gene flow is moderate. About 44% of genetic variation is found among populations, suggesting that most populations exchange pollen or dispersed seeds occasionally.

Population Dynamics: Population sizes of wedgeleaf eryngium fluctuate widely, with the largest populations found shortly after fire and in disturbed areas. Local population sizes and densities are larger than most other Florida scrub endemics. Population sizes peak 6-10 years postfire. Subsequent declines can be steep, and most populations disappear (aboveground) from sites 30-34 years postfire. Wedgeleaf eryngium populations may persist longer in disturbed areas and extremely xeric, open sites. Seeds have persistent dormancy and most populations recover from fire from a persistent soil seed bank. Survival of seeds in the seed bank is probably high. Occasionally, some plants resprout in areas with very low fire intensity. Growth, survival, and fecundity are markedly higher shortly after fire and, over time, for seedling cohorts originating shortly after fire. These results parallel results from transplant experiments in patches of different time-since-fire. Finite rates of increase are greater than one only within the first decade postfire, decreasing thereafter. Seedling numbers vary quite widely, and are highest during wet spring weather and in recently burned areas. Allelopathy by Florida rosemary suppresses seed germination more in E. cuneifolium than in co-occurring target species, suggesting that increasing coverage of Florida rosemary may impact seedling recruitment of E. cuneifolium via allelopathy. Field transplant experiments show that Florida rosemary, compared to shrubby oaks, inhibits growth of E. cuneifolium transplants. Again, other species are less sensitive. This result could be due to allelopathy, belowground competition for water and nutrients, or other mechanisms. The demography of wedgeleaf Eryngium is negatively affected by nearby Florida rosemary shrubs. Its distribution among habitat patches is skewed toward larger and less isolated patches, strongly suggesting that metapopulation dynamics play a role in its distribution.

Interesting Facts: Among the many endemic plant species that occupy white sand habitats in Florida scrub, wedgeleaf eryngium has the greatest specialization for open microsites and recently burned areas, and seems particularly vulnerable to allelopathy from Florida rosemary. It also has an extremely narrow geographic range, little genetic variation, and rapid population crashes as sites age between fires. Fire return intervals greater than 20 years are predicted to cause substantial extinction risks for this species, but rosemary scrub sites are generally burned at longer fire return intervals.

Data Collected by Archbold Biological Station’s Plant Ecology Lab: We have collected data on the survival, growth, and fertility of individual plants since 1988 from 11 populations at Archbold Biological Station. Ten years of these data underlie a PVA. Several populations at other sites have been studied for shorter periods of time. Additional populations have been added at Archbold in recent years. Most plants are visited annually. More intensive surveys for seedling appearance and survival are conducted in the spring of each year at certain sites, using fixed quadrats. We also have studied germination biology, genetic variation, pollination, breeding biology, competitive ability, and allelopathic effects of Florida rosemary on wedgeleaf Eryngium.

Data Availability: projection matrices and data summaries will be available shortly on our website

Contact Person: Eric S. Menges.

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