Phylogeographic structure of Pinus strobiformis Engelm. across the Chihuahuan Desert filter‐barrier

Abstract

Aim To explore the genetic and phylogeographic structure of a temperate forest species, Pinus strobiformis Englem., in a subtropical region in the context of climate change during the Pleistocene. It is expected that the colder conditions during glacial stages favoured range expansions of P. strobiformis, thus promoting gene flow.Location Mexico and the United States.Methods Estimates of genetic diversity and structure were obtained using chloroplast microsatellite loci of 23 populations of P. strobiformis across its entire range, seven neighbouring populations of Pinus ayacahuite Ehrenb. ex. Schtdl, and one population of Pinus flexilis James. ResultsThe genetic diversity of P. strobiformis (H e = 0.856) was found to be high, especially in western populations, whereas eastern populations were less variable and more genetically similar to P. ayacahuite of central Mexico. We found evidence of significant phylogeographic structure (N ST = 0.444; P = 0.026), high genetic structure (R ST = 0.270), and isolation by distance. Pairwise R ST and samova (spatial analysis of molecular variance) results indicated an east-west partition of genetic variation, with populations within each group showing little differentiation and no isolation by distance. Main conclusionsThe phylogeographic structure of P. strobiformis across the entire range was pronounced, with two main genetic and geographic groups separated by the Chihuahuan Desert. However, within each of the two groups there was little population differentiation and no isolation by distance, suggesting genetic connectivity as a result of population expansions within these areas during glacial stages.

Mosaic genetic differentiation along environmental and geographic gradients indicate divergent selection in a white pine species complex

“…Since P. ayacahuite is geographically close to P. strobiformis, and there is evidence of introgression (Perez de la Rosa 1993; Ortíz-Medrano et al 2008; Moreno-Letelier and Piñero 2009), we expected a higher genetic similarity at all nuclear loci. However, what we observe is that only housekeeping genes show a pattern of high differentiation similar to cytoplasmic markers between these two species (Moreno-Letelier and Piñero 2009;Moreno-Letelier et al 2013), but candidate loci show lower differentiation. High differentiation in housekeeping genes could be the result of an older divergence between these two species.…”

“…Our results clearly support IBE of P. flexilis, as it is both ecologically (MorenoLetelier et al 2013), and genetically differentiated from its sister species at candidate loci. However, in addition to the pattern of IBE in candidate genes, genetic differentiation of housekeeping genes and cytoplasmic markers between P. ayacahuite and P. strobiformis suggests that isolation by distance, genetic drift and secondary contact could have also played a role the observed genetic patterns of these two species (Moreno-Letelier and Piñero 2009;Strasburg et al 2012;Abbott et al 2013). In either case, these combined factors could help explain the recent diversification of pines in North America (Gernandt et al 2008), which has resulted in high ecological and morphological diversity, despite widespread shared polymorphism (Syring et al 2007a, b;Moreno-Letelier and Piñero 2009;Willyard et al 2009;Jardón-Barbolla et al 2011).…”

“…However, in addition to the pattern of IBE in candidate genes, genetic differentiation of housekeeping genes and cytoplasmic markers between P. ayacahuite and P. strobiformis suggests that isolation by distance, genetic drift and secondary contact could have also played a role the observed genetic patterns of these two species (Moreno-Letelier and Piñero 2009;Strasburg et al 2012;Abbott et al 2013). In either case, these combined factors could help explain the recent diversification of pines in North America (Gernandt et al 2008), which has resulted in high ecological and morphological diversity, despite widespread shared polymorphism (Syring et al 2007a, b;Moreno-Letelier and Piñero 2009;Willyard et al 2009;Jardón-Barbolla et al 2011). A similar pattern of recent diversification has been observed in other Neotropical plant groups, such as firs, junipers, oaks and lupins (Hughes and Eastwood 2006;Mao et al 2010;Aguirre-Planter et al 2012;Petit et al 2013;Moreno-Letelier et al 2014).…”

“…1a; Farjon and Styles 1997;Bower et al 2011). These species are very closely related, show a very high degree of shared polymorphism in standard markers and their phylogenetic relationships are not fully resolved (Syring et al 2007a, b;Moreno-Letelier and Piñero 2009;Moreno-Letelier et al 2013). However, significant climatic niche differentiation has been identified in this group based on climatic niche modelling, as well as differences in seed and cone morphology, needle length and growth rates (Perez de la Rosa 1993; Steinhoff and Andersen 1971;Moreno-Letelier et al 2013).…”

Short Communication Cross-species transferability of eastern white pine (Pinus strobus) nuclear microsatellite markers to five Mexican white pines

“…Published molecular studies based on isozymes and DNA markers (low-copy unlinked nuclear loci and RAPDs) revealed low genetic diversity in this species (Castillo et al, 2009). Molecular marker-based studies in the P. strobiformis-P. ayacahuite complex have been limited to genetic diversity assessment using isozymes (Hernández-Gónzalez 1990;Ledig, 1998), RAPDs (Castro-Félix et al, 2006, and chloroplast microsatellite markers (Ortíz-Medrano et al, 2008;Moreno-Letelier and Piñero, 2009).…”