Genetic diversity and differentiation in Zamia furfuracea (Zamiaceae): an endangered, endemic and restricted Mexican Cycad

Zamia furfuracea is a cycad endemic to coastal habitats of southeast Mexico and of high ecological and horticultural importance. It is threatened with extinction due to the declining population size, caused mainly by livestock raising, urban development, and poor environmental management. This work aimed to determine the genetic diversity and structure of six natural populations of Z. furfuracea throughout their known distribution range. To determine the genetic variation, ten molecular markers of repeated simple sequences (SSR) were used. A Bayesian assignment model, molecular variance analysis and bottleneck tests, and identification of loci with non-neutral heritage were also performed. A lower genetic diversity was identified in the southern population (Capulteolt). Four genetic groups were identified (K = 4). Ancestral polymorphism and management resulted in an increased genetic similarity between the populations of ＂Ciénega del Sur,＂ ＂Toro Prieto,＂ and ＂Playa Escondida＂. ＂Capulteolt＂ was the most differentiated population; a historical reduction in the population size was observed, leading to the loss of some alleles by putative directional natural selection. This study reveals the ＂Capulteolt＂ population's low genetic diversity as well as the presence of increased differentiation in the geographical limits of the species' distribution range.