Genetic Variation among Rare Florida Endemic Hymenocallis henryae Populations and the Implication for Conservation and Management

Hymenocallis henryae is a rare, charismatic spider lily endemic to the Florida panhandle. Currently under review to determine if listing under the Endangered Species Act is warranted, this species has undescribed genetic diversity, information crucial to the listing process. We conducted field observations of 21 historic populations across the species' geographical range and performed genomic analyses of 279 individuals from 19 extant populations. Most populations had fewer than 40 individuals, while populations with >100 individuals were found exclusively on managed lands. Genetic diversity was uniformly low within populations (H-E: 0.074-0.093), with low to moderate inbreeding coefficients (F-IS: 0.068-0.431). Genetic differentiation was relatively low among most populations (F-ST: 0-0.098), although there was statistical support for isolation by distance. In addition, we found high genetic similarity and lack of population structure across the species range. Clonal propagation through fused bulbs is a common reproductive strategy. We confirmed current threats (habitat change, residential development, fire suppression) and identified several coastal populations threatened by sea level rise. It is recommended to continue with in situ protection and management as well as the establishment of ex situ living collections to preserve populations most at risk of extirpation from habitat loss and degradation.