Distribution and genetic diversity of South Florida Tephrosia shed light on past cultural use

O_LIThe genus Tephrosia (Fabaceae), the hoary peas, contain high levels of rotenone, which has a long history of human use as a fish poison. We examine the distribution of Tephrosia angustissima, in South Florida to clarify patterns of genetic relatedness and shed light on human plant movement before European contact. Several populations of Tephrosia angustissima with a history of taxonomic uncertainty exist in South Florida and the neighboring Caribbean Islands. C_LIO_LITo clarify relationships in this group, and to elucidate the conservation status of populations in Everglades National Park and Big Cypress National Preserve, we used restriction site associated DNA sequencing (RAD-SEQ) on 94 samples from South Florida and three locations in southwest Puerto Rico. C_LIO_LIAnalysis of variation in SNP markers by the Bayesian STRUCTURE algorithm and principal coordinate analysis both separated the samples into three groups. These three groups were likely separate colonization events of Florida. Genetic diversity is moderate in all of the groups, with only limited evidence of a bottleneck in some of the disjunct South Florida populations. C_LIO_LIOverall, the human association of this group is consistent with a history of human use, suggesting conservation efforts for these taxa should consider their pre-Columbian human associations. C_LI Societal impact statementA great many endangered plant taxa exhibit patterns of edaphic specialization, occurring on particular substrates such as karst or serpentine soils. Human activities, such as the construction of shell middens, can create edaphically unique substrates. In the Americas, post-Columbian land use changes coupled with extensive loss of indigenous cultural knowledge, has created areas where associations of cultivated plants with human-generated habitats may be lost. Here we use population genetic approaches to examine rare Tephrosia (hoary pea) taxa from South Florida, a group of plants that produce rotenone that has been used by many indigenous groups as a fish poison. We find evidence of multiple introductions from the broader Caribbean region and an association with anthropogenic habitats such as shell middens. In efforts to conserve rare hoary peas in Florida, an understanding of past use of the landscape by native Americans is essential.