Yolanda Salinas-Moreno

Factors Influencing the Geographical Distribution of Dendroctonus rhizophagus (Coleoptera: Curculionidae: Scolytinae) in the Sierra Madre Occidental, México

ABSTRACT The bark beetle, Dendroctonus rhizophagus Thomas & Bright, is endemic to the Sierra Madre Occidental (SMOC) in México. This bark beetle is a major pest of the seedlings and young saplings of several pine species that are of prime importance to the nations forest industry. Despite the significance of this bark beetle as a pest, its biology, ecology, and distribution are poorly known. Three predictive modeling approaches were used as a first approximation to identify bioclimatic variables related to the presence of D. rhizophagus in the SMOC and to obtain maps of its potential distribution within the SMOC, which is a morphotectonic province. Our results suggest that the bark beetle could have an almost continuous distribution throughout the major mountain ranges of the SMOC. This beetle has a relatively narrow ecological niche with respect to some temperature and precipitation variables and inhabits areas with climatic conditions that are unique from those usually prevalent in the SMOC. However, the bark beetle has a broad ecological niche with respect to the number of hosts that it attacks. At the macro-scale level, the D. rhizophagus distribution occurs within the wider distribution of its main hosts. The limit of the geographical distribution of this bark beetle coincides with the maximum temperature isotherms. Our results imply a preference for temperate habitats, which leads to the hypothesis that even minor changes in climate may have significant effects on its distribution and abundance.

Genetic Structure of Dendroctonus mexicanus (Coleoptera: Curculionidae: Scolytinae) in the Trans-Mexican Volcanic Belt

Abstract It is assumed that geographic isolation of Dendroctonus Erichson species populations or their plant hosts determines genetic structure. This structure can be analyzed with respect to the biogeographic pattern that describes the species in a region. The Trans-Mexican Volcanic Belt (TMVB) is located between the Neartic and Neotropical regions and is a center of diversification and endemism of trees in the genus Pinus L. Dendroctonus mexicanus Hopkins is polyphagous within Pinus species and has a continuous geographic distribution across the TMVB. We explored whether the population genetic structure of D. mexicanus is reflective of the distribution pattern of the Dendroctonus species that occur in the TMVB. Twelve gene loci were analyzed by isozyme electrophoresis in 17 populations found on pines from the Leiophyllae subsection. Allele frequencies, average heterozygosity, heterozygosity by locus, deviations from Hardy–Weinberg equilibrium (HWE), F-statistics among populations, and average genetic flow were calculated. Genetic structure was determined using the relationship between FST versus geographic distances among populations. Genetic relations among populations were established by neighbor-joining and principal components analysis by using Nei’s genetic distances. Dendrogram reliability was assessed by bootstrap analysis and cophenetic correlation coefficient by using the Mantel test. Results show that heterozygosity of D. mexicanus is similar to other scolytids. A high proportion of loci were out of HWE by homozygous excess, which may be explained by multiple factors. The scarce number of fixed alleles, the allele variation pattern, pairwise genetic distances, and F-statistics suggest a model of isolation by distance for D. mexicanus in the TMVB resulting from recent dispersal events.