Integrative Analysis of <i>Diphasiastrum digitatum</i> Holub: Unveiling Genetic Variation and Ecological Adaptations for Sustainable Ecosystem Management

Understanding the diversity and ecological evolutionary history of plant species is crucial for addressing the current biodiversity crisis and comprehending the processes by which organisms fill ecological and geographic spaces. In this study, we present a comprehensive analysis of the diversity and evolutionary history of <i>Diphasiastrum digitatum</i> Holub from the lycophyte lineage of plants, using microsatellite genotyping data and biogeographic analyses. Based on the available transcriptome assembly, we generated numerous markers and utilized 13 robust microsatellite markers to genotype a collection of 402 specimens from the Eastern US (VT; VA; NC; TN). In accordance with the accepted phylogeny, cross-amplification tests demonstrated a closer relationship between <i>D. digitatum</i> and <i>Diphasiastrum</i> spp. compared with <i>Lycopodium</i> spp. Furthermore, the population genetics analyses identified two genetic clusters within the <i>D. digitatum</i> collection and suggested ongoing divergence and expansion. Isolation-by-distance analysis indicated that geographic distance had a minimal effect on differentiation, whereas environmental variables related to water regime were strongly associated with the genetic variance. Ecological niche modeling showed a post-Last Glacial Maximum expansion of <i>D. digitatum</i> from southern refugia, corroborating a similar evolutionary scenario based on our microsatellite data. Overall, this study provides valuable insights into the evolutionary history of clubmosses and highlights the migration events and the environmental factors that shaped their current distribution.