Abstract
The Southeastern Coastal Plain Floristic Province is a recently described biodiversity hotspot, with new vascular plant species being discovered every year. Biodiversity hot spots, by definition, have high habitat loss, making it all the more important to understand the preferred habitat of endemic species to facilitate their conservation. Asclepias feayi is a milkweed endemic to Florida characterized by a delicate and cryptic morphology, which makes it difficult to detect except when it is in bloom. Herbarium records and vascular plant inventories that have recorded A. feayi do not clearly indicate whether this species is a generalist or a specialist. This study aimed to identify the habitat type in which populations of Asclepias feayi were found, collect demographic data to characterize typical populations, measure microhabitat conditions, and record population responses to disturbances such as fire or proximity to trails. Study sites were selected from 15 different conservation lands where populations were confirmed to exist. One to three 10 m by 10 m plots were established at each site to record relative canopy cover, a list of associate species and their relative cover, a count of total Asclepias feayi, and population demographics (vegetative juveniles, vegetative adults, and reproductive adults). Circular, nonoverlapping 1 m2 plots were centered over one to five randomly selected A. feayi to measure canopy cover over the plant, relative cover of bare soil, leaf litter, and vegetation, associate species, density of A. feayi, and spatial distance from trees and shrubs. Over the course of this study, A. feayi was found in areas of mesic or dry flatwoods, or transitional areas between flatwoods and scrubby flatwoods with little to no canopy. Shrub cover was predominantly low-growing Serenoa repens with spacious gaps filled with slow-growing bunchgrasses (predominantly Aristida beyrichiana) and other herbaceous species. Microhabitat cover was mostly bare soil with low leaf litter. Microhabitat associate species were predominantly herbaceous. Demographic data collected showed a similar composition of juveniles, adults, and reproductive adults across all regions and habitats. Disturbance increased the percentage of blooming adults. Populations that underwent a burn that year had nearly double the number of reproductive adults (p = 0.001). Reproductive activity seemed to be further increased by plot proximity to trailside areas (p = 0.057), suggesting this species may be dependent on fire for reproductive success. Associate species at the macroplot level were relatively consistent across all plots, with multivariate analyses showing strong overlap regardless of geographic location or habitat type. Multidimensional scaling plots analyzing macro and microplot species composition emphasized this, with points for both plot types resembling shotgun blasts. Consistent habitat structure and overlapping species composition suggests A. feayi is a dry or scrubby flatwoods specialist that seems to prefer to grow in grassy, herbaceous gaps with open soil. Reproductive data suggests that blooming is increased by fire. Taken together, this suggests A. feayi requires regular, frequent fire for reproductive success and to maintain its preferred microhabitat structure within the larger habitat mosaic.
