Coleoptera Associated with Decaying Wood in a Tropical Deciduous Forest.

Coleoptera is the largest and diverse group of organisms, but few studies are dedicated to determine the diversity and feeding guilds of saproxylic Coleoptera. We demonstrate the diversity, abundance, feeding guilds, and succession process of Coleoptera associated with decaying wood in a tropical deciduous forest in the Mixteca Poblana, Mexico. Decaying wood was sampled and classified into four stages of decay, and the associated Coleoptera. The wood was identified according to their anatomy. Diversity was estimated using the Simpson index, while abundance was estimated using a Kruskal-Wallis test; the association of Coleoptera with wood species and decay was assessed using canonical correspondence analysis. Decay wood stage I is the most abundant (51%), followed by stage III (21%). We collected 93 Coleoptera belonging to 14 families, 41 genera, and 44 species. The family Cerambycidae was the most abundant, with 29% of individuals, followed by Tenebrionidae with 27% and Carabidae with 13%. We recognized six feeding guilds. The greatest diversity of Coleoptera was recorded in decaying Acacia farnesiana and Bursera linanoe. Kruskal-Wallis analysis indicated that the abundance of Coleoptera varied according to the species and stage of decay of the wood. The canonical analysis showed that the species and stage of decay of wood determined the composition and community structure of Coleoptera.

Quaternary origin and genetic divergence of the endemic cactus Mammillaria pectinifera in a changing landscape in the Tehuacán Valley, Mexico.

The endemic Mexican cactus, Mammillaria pectinifera, shows low dispersal capabilities and isolated populations within the highly dissected landscape of Tehuacán Valley. These characteristics can restrict gene flow and act upon the genetic divergence and speciation in arid plants. We conducted a phylogeographic study to determine if the origin, current distribution, and genetic structure of M. pectinifera were driven by Quaternary geomorphic processes. Sequences of the plastids psbA-trnH and trnT-trnL obtained from 66 individuals from seven populations were used to estimate genetic diversity. Population differentiation was assessed by an analysis of molecular variance. We applied a stepwise phylogenetic calibration test to determine whether species origin and genetic divergence among haplotypes were temporally concordant with recognizable episodes of geomorphic evolution. The combination of plastid markers yielded six haplotypes, with high levels of haplotype diversity (h = 0.622) and low nucleotide diversity (π = 0.00085). The populations were found to be genetically structured (F(ST) = 0.682; P < 0.00001), indicating that geographic isolation and limited dispersal were the primary causes of genetic population differentiation. The estimated origin and divergence time among haplotypes were 0.017-2.39 and 0.019-1.237 mya, respectively, which correlates with Pleistocene tectonics and erosion events, supporting a hypothesis of geomorphically-driven geographical isolation. Based on a Bayesian skyline plot, these populations showed long term demographic stability, indicating that persistence in confined habitats has been the main response of this species to landscape changes. We conclude that the origin and haplotype divergence of M. pectinifera were a response to local Quaternary geomorphic evolution.