Population genetic structure of an extremely logged tree species Guaiacum sanctum L. in the Yucatan Peninsula, Mexico

Abstract

Habitat disturbance in tropical forests has affected the viability of several tree species. In Mexico, populations of Guaiacum sanctum have disappeared in some regions due to a strong habitat reduction which could endanger the genetic diversity and connectivity of remnant populations. In this study, 17 populations from the Yucatán Peninsula were analyzed with seven nuclear microsatellites. Several parameters describing the genetic diversity were estimated. The genetic structure was evaluated using Bayesian cluster analysis. Population bottlenecks, effective population size, and genetic connectivity were estimated. Populations of G. sanctum showed high values of genetic diversity. Two genetic groups with contrasting distributions were detected, the first one located in northern Yucatán and Quintana Roo and the second, in southern Campeche. Evidence of population bottleneck was detected only for Campeche populations. Also, we found indications of significant levels of inbreeding and a low effective population size. The connectivity analysis revealed exchange among populations of G. sanctum but the habitat fragmentation may act to impede gene flow, contributing to the division observed between clusters. This genetic differentiation was possibly caused by environmental pressures, although effects of historical extensive logging practices occurred in southern Mexico during the last few decades cannot be discarded. Fragmentation has a negative effect on ecosystem services and on the availability of favorable sites for seedling establishment, which could disturb pollination and dispersion processes, modifying in the long term the effective population size.

Genetic diversity, gene flow, and differentiation among wild, semiwild, and landrace chile pepper (Capsicum annuum) populations in Oaxaca, Mexico

“…The resulting network graph represents the populations as nodes (locations or landraces for each one of our analyses), with node size reflecting within‐population genetic variance. Nodes are connected by “edges” (lines) whose length is inversely proportional to the genetic covariance between a pair of nodes, thus reflecting the among‐population component of genetic variation (Dyer and Nason, 2004; Oyama et al, 2016). Only 26 locations and 12 landraces of C. annuum and one C. frutescens populations were included in this analysis; locations and landraces with less than four individuals cannot be analyzed by the program because their within‐population variance and genetic covariances cannot be confidently assessed (Dyer and Nason, 2004).…”

Genetic and Ecological Divergence of Cinnamon HummingbirdAmazilia rutila(Aves: Trochilidae) Continental Populations Separated by Geographical and Environmental Barriers

“…The biogeography of the region is not only influenced by the effects of the formation and emergence of the Yucatán Peninsula but also by those related to the geology of and tectonic activity and mountain ranges on the Maya block, between the biogeographic breaks Isthmus of Tehuantepec and Motagua-Polochic-Jocotán fault system (Gutiérrez-García & Vázquez-Domínguez, 2012). Although these geological and topographical features and isolation by mountain ranges in the Maya block surely influenced the evolutionary history of Mesoamerican species (e.g., González et al, 2011; Guevara-Chumacero et al, 2010; Gutiérrez-García & Vázquez-Domínguez, 2012; Jiménez & Ornelas, 2016; Rodríguez-Gómez & Ornelas, 2014; Williford et al, 2016), few studies have included phylogeographies of species with patterns of historical divergence and population genetic differentiation between groups of populations from Chiapas and from the Yucatán Peninsula (Gutiérrez-García & Vázquez-Domínguez, 2012; Licona-Vera et al, 2018b; Ortiz-Rodriguez et al, 2020; Oyama et al, 2016). In these studies, the observed patterns of genetic divergence are consistent with the hypothesis that isolation of the dry Yucatán province by semideciduous tropical rain forest along the Petén region and Chiapas restricted northward gene flow from locations of the Pacific slope in Mexico into the TDF in the extreme NW portion of the Yucatán peninsula (an “ecological barrier”; Licona-Vera et al, 2018b and references therein).…”

Landscape genetics of Mexican biodiversity: A review

“…In plants, detection of barriers to gene flow were more explorative, but all made a link of identified barriers with habitat fragmentation effects. For instance, for an endangered tropical tree (Guaiacum sanctum) across a fragmented landscape in the Yucatán Peninsula, Oyama et al (2016) detected seven barriers to gene flow, which were associated to habitat fragmentation, although the authors did not discard effects of historical barriers. A similar effect was found for the threatened orchid species Laelia speciosa in the fragmented habitat of the Cuitzeo basin (Rojas-Mendez et al, 2017).…”