Population Genetic Diversity and Species Distribution Evaluation of <i>Bletilla striata</i> (Orchidaceae) in Southwest China Using <scp>SSR</scp> Markers

We assessed the genetic diversity and population structure of the protected orchid <i>Bletilla striata</i> across 18 wild populations in southwestern China. Eight pairs of simple sequence repeat (SSR) molecular markers were employed for its genetic diversity and population structure analyses, while the optimized Maxent model was utilized to predict changes in the habitat distribution under historical conditions and three future climate scenarios (SSP126, SSP245, and SSP585) with 141 natural distribution data and 19 climatic factors. The results revealed an average number of alleles (<i>Na</i>) of 3.549 and an effective number of alleles (<i>Ne</i>) of 2.636, with a mean polymorphic information content (<i>PIC</i>) of 0.748 across the <i>B. striata</i> populations. Moderate genetic diversity was observed (observed heterozygosity, <i>Ho</i> = 0.402; expected heterozygosity, <i>He</i> = 0.509), with 73% of the total variation found within populations, while the 02 population in Zhijin Guizhou exhibited relatively high genetic differentiation (<i>Ho</i> = 0.675, <i>He</i> = 0.658). UPGMA clustering, population structure analyses, and principal component analysis identified two primary subgroups within <i>B. striata</i>. Among the 19 climate variables analyzed, four temperature-related factors and two precipitation-related factors were identified as key drivers influencing the geographical distribution of <i>B. striata</i>. Future projections for the 2050s and 2070s under varying climate scenarios indicate a northward expansion of suitable habitats for <i>B. striata</i>. The proportion of suitable habitat area is expected to increase from 288.3450 × 10⁴ km² under historical conditions (1970-2000) to 351.9792-405.6077 × 10⁴ km² (2050s-2070s). The wild <i>B. striata</i> populations in southwestern China and adjacent regions represent valuable germplasm resources with high genetic diversity, offering significant potential for artificial cultivation initiatives. Moreover, predictions of future distribution dynamics provide critical insights to guide the conservation, development, and sustainable utilization of <i>B. striata</i>.