Population structure and genetic connectivity in the endangered Pectis imberbis: addressing conservation and genetic gaps in the Arizona Sky Islands

The conservation of rare and endangered plants requires understanding of genetic diversity and connectivity to mitigate the effects of habitat fragmentation and environmental change. Pectis imberbis (Gray), a perennial herb endemic to the Arizona Sky Islands, is listed as endangered due to recent extirpations, population declines, habitat loss, and restricted range. To address critical knowledge gaps in P. imberbis conservation, we assessed population structure, genetic diversity, and connectivity across its range using single nucleotide polymorphisms (SNPs) generated through RADseq. We identified three genetically distinct population clusters, with limited gene flow among populations located in the Huachuca, Santa Rita, and Atascosa-Pajarito Mountain ranges. Estimated effective migration surfaces revealed barriers to gene flow, particularly around Montezuma Pass and the Patagonia Mountains, which corresponded with demographic declines and recent extirpations. Pollinator visitation and floral network analyses showed consistent overlap of key pollinator taxa across populations but suggested limited pollen transfer over large distances. These findings highlight the need for targeted restoration efforts to enhance genetic connectivity, such as establishing stepping-stone populations in regions of limited migration. Future research should focus on testing adaptive variation to guide restoration actions taken to increase connectivity. By integrating genetic, demographic, and pollinator data, this work directly informs P. imberbis conservation, and more generally, contributes to understanding of rare species conservation in fragmented landscapes.