Introduction / Background / Justification
According to the red list of oaks 2020, approximately 31% of Quercus species are threatened with extinction worldwide. Mexico stands out as the country with the highest oak species richness, but also as the second one with the largest number of threatened species (32). Unfortunately, for most of these threatened species there is a lack of demographic, genetic and ecological information that would be essential for their conservation.
In this study, we focused on the population genetics of two threatened Mexican oak species, Quercus brandegeei and Q. hirtifolia, that represent contrasting evolutionary and ecological contexts, but both with restricted geographical ranges and reduced population sizes.
Most known populations of both species were sampled. Genetic diversity was assessed using nuclear simple sequence repeats (nSSRs) and chloroplast DNA (cpDNA) sequences. Standard measures of genetic variation and differentiation were estimated and complemented with landscape genetics analyses used to assess environmental and topographical factors influencing pollen and seed-mediated gene flow.
Genetic variation at nuclear DNA was moderate and low at cpDNA in both species. There was evidence of low effective population size, reduced genetic connectivity and significant effects of genetic drift and inbreeding in the two oaks, but particularly in Q. brandegeei.
The comparison of our results with those obtained in other endangered and non-endangered oak species provides an opportunity to identify genetic erosion processes that may further compromise the long-term survival of threatened species and to propose informed management actions.
Quercus, effective population size, genetic variation, gene flow