Conservation implications of genetic structure in the narrowest endemic quillwort from the Eastern Amazon

The quillwortIsoëtes cangaeis a critically endangered species occurring in a single lake in Serra dos Carajás, Eastern Amazon. Low genetic diversity and small effective population sizes (Ne) are expected for narrow endemic species (NES). Conservation biology studies centered in a single species show some limitations, but they are still useful considering the limited time and resources available for protection of species at risk of extinction. Here, we evaluated the genetic diversity, population structure,Ne, and minimum viable population (MVP) ofI. cangaeto provide information for effective conservation programs. Our analyses were based on 55 individuals collected from the Amendoim Lake and 35,638 neutral SNPs. Our results indicated a single panmictic population, moderate levels of genetic diversity, andNein the order of thousands, contrasting the expected for NES. Negative FISvalues were also found, suggesting thatI. cangaeis not under risk of inbreeding depression. Our findings imply thatI. cangaecontains enough genetic diversity to ensure evolutionary potential and that all individuals should be treated as one demographic unit. These results provide essential information to optimize ex situ conservation efforts and genetic diversity monitoring, which are currently applied to guideI. cangaeconservation plans.