Nuclear and chloroplast DNA phylogeography reveals high genetic diversity and postglacial range expansion in Quercus mexicana

Abstract

PremisePhylogeographical studies are fundamental for understanding factors that influence the spatial distribution of genetic lineages within species. Population expansions and contractions, distribution shifts, and climate changes are among the most important factors shaping the genetic compositions of populations.MethodsWe investigated the phylogeography of an endemic oak, Quercus mexicana (Fagaceae), which has a restricted distribution in northeastern Mexico along the Sierra Madre Oriental and adjacent areas. Nuclear and chloroplast DNA microsatellite markers were used to describe the genetic diversity and structure of 39 populations of Q. mexicana along its entire distribution area. We tested whether population expansion or contraction events influenced the genetic diversity and structure of the species. We also modeled the historical distributional range of Q. mexicana (for the Mid Holocene, the Last Glacial Maximum, and the Last Interglacial) to estimate the extent to which climate fluctuations have impacted the distribution of this oak species.ResultsOur results revealed high genetic diversity and a low genetic structure in Q. mexicana populations. Ecological niche models suggested historical fluctuations in the distributional range of Q. mexicana. Historical range changes, gene flow, and physical barriers seem to have played an important role in shaping the phylogeographic structure of Q. mexicana.ConclusionsOur study indicates that the genetic structure of Q. mexicana may have been the result of responses of oak trees not only to heterogeneous environments present in the Sierra Madre Oriental and adjacent areas, but also to elevational and latitudinal shifts in response to climate changes in the past.This article is protected by copyright. All rights reserved.

Paleo-climates and past introgression explain the spatio-temporal distribution of genetic structure in Triodanis perfoliata

“…As such, there remains a need for studies that incorporate temporally relevant paleoclimatic data with genomic data to understand drivers of phylogenetics and population genomics (however see Evans et al 2009, Prates et al 2016, Rangel et al 2018, Guillory and Brown 2021. The advantages of including these types of data can be seen through studies of several oak species in the Mexican highlands in which high genetic diversity but low genetic structure is explained through historical processes such as range stability, elevational displacement, and dynamic gene flow between populations (Peñaloza-Ramírez et al 2020, Sánchez-Acevedo et al 2023). The dynamic nature of climate, especially over thousands or millions of years, alters the landscape and therefore the connectivity of populations and movement of individuals.…”