Species-rich bark and ambrosia beetle fauna (Coleoptera, Curculionidae, Scolytinae) of the Ecuadorian Amazonian Forest Canopy.

Canopy fogging was used to sample the diversity of bark and ambrosia beetles (Coleoptera, Curculionidae, Scolytinae) at two western Amazonian rainforest sites in Ecuador. Sampling was conducted by Dr Terry Erwin and assistants from 1994-2006 and yielded 1158 samples containing 2500 scolytine specimens representing more than 400 morphospecies. Here, we analyze a subset of these data representing two ecological groups: true bark beetles (52 morphospecies) and ambrosia beetles (69 morphospecies). A high percentage of these taxa occurred as singletons and doubletons and their species accumulation curves did not reach an asymptote. Diversity estimates placed the total scolytine species richness for this taxon subset present at the two sites between 260 and 323 species. The α-diversity was remarkably high at each site, while the apparently high ß-diversity was an artifact of undersampling, as shown by a Monte Carlo resampling analysis. This study demonstrates the utility of canopy fogging for the discovery of new scolytine taxa and for approximate diversity assessment, but a substantially greater sampling effort would be needed for conclusive alpha as well as beta diversity estimates.

Polyphyly of Xylosandrus Reitter inferred from nuclear and mitochondrial genes (Coleoptera: Curculionidae: Scolytinae).

The Xyleborina ambrosia beetle genus Xylosandrus contains 54 species, several of which are of economic importance. The monophyly of the genus was tested using a data set comprised of multiple gene loci: 28S rDNA; the mitochondrial gene cytochrome oxidase I (COI); and the nuclear genes arginine kinase (ArgK), rudimentary (CAD), and Elongation Factor 1alpha (EF-1alpha). The nuclear protein-coding genes CAD and ArgK were used for the first time in phylogenetics of Scolytinae. Analyses were performed using Parsimony and Bayesian optimality criteria. Our analyses included 43 specimens representing 15 Xylosandrus species and 20 species from Amasa, Anisandrus, Cnestus, Euwallacea and Xyleborus, and two species from the outgroup genus Coccotrypes. All analyses recovered a polyphyletic Xylosandrus. Several species of Xylosandrus were consistently placed in clades with the genera Anisandrus and Cnestus with high support values (100% bootstrap support). Among these, was the economically important invasive species X. mutilatus, which was consistently recovered as part of the "Cnestus" clade. In our analyses, both CAD and ArgK demonstrated phylogenetic utility across varying nodal depths. Despite the selection of genes with signals at complementary phylogenetic depths, the data set used herein did not resolve the phylogeny of Xylosandrus and related genera. Since the taxon sample available for molecular work represents only a fraction of Xylosandrus species, a complete revision that combines molecular and morphological data in a total evidence approach is recommended for the genus.

A comparison of bark and ambrosia beetle communities in two forest types in northern Thailand (Coleoptera: Curculionidae: Scolytinae and Platypodinae).

Many ecological studies of tropical insects are based on small sample sizes or lack sampling scheme rigor, which prevents testing ecological hypotheses and comparing samples from different sites and times. Here we present the results of quantitative trapping of bark and ambrosia beetles over 2 yr at two localities in northern Thailand separated by 5 km, 1,100 m in altitude, and in different forest types. Beetles were collected using a spatially and temporally standardized sampling scheme, followed by a quantitative analysis of community composition and its responses to environmental variables and trapping techniques. In total, 118 species were collected, but the species accumulation curves show little sign of leveling off. Based on slightly different species accumulation rates, the more humid site has a little higher species richness. Species composition was significantly different between the sites, which was not a result of undersampling of rare species. alpha diversity at each site contributes to the regional diversity more than the turnover of species between the sites (beta diversity). Mean annual temperature and humidity have larger effects on the community species composition than seasonal fluctuations of temperature and humidity at each site--beetles do choose their environment but are aseasonal. The site with greater humidity supported significantly more species living in a symbiosis with fungi (ambrosia beetles), whereas the drier and more disturbed site hosted a greater number of circumtropical colonizer species. Each of the different types of trap had a bias for certain taxonomic groups. The results show that even modest samples, if properly structured and analyzed, can answer many ecological questions and can serve in biodiversity comparisons on broad scales.