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Distribution: Florida jointweed is endemic to central Florida endemic, found in Highlands and Polk counties on the Lake Wales, Winter Haven, and Bombing Range Ridges. It is federally and state endangered.

Habitats: This species is found on excessively to moderately well-drained white and gray sand soils. Florida jointweed is primarily associated with rosemary phase of sand pine scrub, but is also occasional in sandy openings within oak scrub/scrubby flatwoods. It is also common in disturbed areas including sandy roadsides within these habitats.

Life History: Florida jointweed is a short-lived perennial, taprooted herb, flowering one or more years, not often living beyond third year. Plants have a rosette of spiky needle-like leaves with one to forty wiry green or reddish flowering stems branching from base. Stems can be as tall as 60 cm. The leaves are green or dark red, narrow, ascendant, and alternate. Stems appear jointed; ocrea bear 2 or more long bristles. The flowers are apetalous with 5 white (hermaphrodite) or pale pink (female) sepals in one to many slender spikes per stem. Fruits are achenes 1-3 mm long.

Phenology: Florida jointweed seedlings recruit in the winter and spring. Flowering occurs in the fall, September through November. Plants overwinter as rosettes.

Breeding System and Pollination: Florida jointweed is gynodioecious: perfect and pistillate flowers are born on different individuals. Perfect individuals have distinct blue-black anthers. It is possible that a few individuals may change gender between years (<10 %).

Genetics: Isozyme studies have found greater heterozygosity in Florida jointweed than in more widely distributed congeners, perhaps because it has not experienced the repeated bottlenecks that can be associated with glaciation.

Population Dynamics: Mortality occurs throughout the year, but recruitment occurs chiefly in winter and spring. Although adults are killed by fire, germination is stimulated by fire or other disturbances that create gaps in vegetation. Seeds have very high viability, occasionally germinating on parent plants. There is little seed dormancy and the species does not form a substantial persistent seed bank. Recruitment varies substantially between populations and years, and in some years recruitment is critical to prevent local extinction. Dynamic population sizes suggest that metapopulation dynamics can explain distributions. Patch (gap) level extinction and recolonization may be related to gap size and isolation. Densities typically range from less than one to 13 plants per m²; density increases with increasing bare sand availability. Populations tend to have a 1:1 sex ratio, although females produce many more seeds than hermaphrodites. Seed production increases with increasing conspecific density.

Interesting Facts: Most of the other rare scrub herbaceous species that do not resprout after fire have a persistent seed bank. Polygonella basiramia and its congeners lack this seedbank. Therefore, its return to burned sites may be delayed by dispersal limitations, especially in large complete burns.

Data Collected by Archbold Biological Station’s Plant Ecology Lab: We collect data on Florida jointweed demography: recruitment, mortality, density, fecundity, and size relative to time-since-fire and anthropogenic disturbance. Nine populations are currently being studied: 1 primitive road, 1 firelane, 7 rosemary balds. Time-since-fire ranges from two to 15 years. All populations have been monitored twice yearly since 1996 except for the firelane site which has census data for 1996 and 1997 and demographic monitoring thereafter.

Data Availability: Summary data are available at this Web site.

Contact Person: Eric S. Menges.

References:

1. Hawkes, C. V. and E. S. Menges. 1995. Density and seed production of a Florida endemic, Polygonella basiramia, in relation to time since fire and open sand. American Midland Naturalist 133: 138-148.
2. Hawkes, C. V. and E. S. Menges. 1996. The relationship between open space and fire for species in a xeric Florida shrubland. Bulletin of the Torrey Botanical Club 123: 81-92.
3. Lewis, P. O. and D. J. Crawford. 1995. Pleistocene refugium endemics exhibit greater allozymic diversity than widespread congeners in the genus Polygonella (Polygonaceae). American Journal of Botany 82: 141-149.

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