The role of niche breadth in oak phylogeography: Quercus glaucoides as a study case

Abstract

Aim: The extent of genetic diversity and its distribution among populations have been associated with species attributes such as mating system, dispersal ability and geographic range size. Another attribute that could contribute to intraspecific phylogeographic patterns is niche breadth, but this has rarely been tested. Here, we ask whether a Mexican oak with a comparatively narrow climatic niche breadth has distinct genetic diversity patterns compared to other codistributed oaks with a broader climatic niche. Location: Mexico. Taxon: Quercus glaucoides M. Martens & Galeotti (Fagaceae). Methods: Descriptors of genetic diversity and structure were calculated for 21 Q. glaucoides populations using chloroplast DNA (cpDNA) and nuclear microsatellites (nSSRs). Historical demographic dynamics were inferred with approximate Bayesian computation (ABC) and past potential distribution models. To test for an association between niche breadth and phylogeographic patterns, we used genetic diversity and differentiation values of Q. glaucoides plus those previously published for 10 other Mexican oak taxa. Niche breadth was estimated for all taxa and linear regressions were performed. Results: Genetic diversity calculated from nSSRs (HO = 0.539; HE = 0.714) was among the lowest and cpDNA differentiation (NST = 0.88) was the highest so far obtained for comparable Mexican oaks. Moderate changes in demographic size and distribution shifts throughout the last glacial cycle were inferred, explaining some of the observed genetic patterns. A positive correlation of HO and a negative correlation of NST with niche breadth were detected across taxa. Main Conclusions: Distinct phylogeographic patterns in Q. glaucoides could be explained because a narrower niche may cause lower historical effective population sizes and more fragmented distributions in comparison to species with a wider niche breadth, even with similar range sizes. Our results indicate that niche breadth would be an interesting ecological attribute to be included in future comparative phylogeographic studies.