Phylogenetic assessment of taxonomic and ecological biodiversity of herbivore beetles in the dry tropical forest

Abstract

The dry tropical forest is the most threatened ecosystem in the tropical areas and any effort towards understanding its function and composition is critical in order to implement conservation measures. In this study we explored, using molecular tools, two aspects of the biodiversity of the Mesoamerican dry forest: species inventories of herbivore beetles (Coleoptera, Chrysomelidae) and their ecological interac- tions with angiosperms. Specifically, we intended to: (1) Assess species diversity of three subfamilies of Chrysomelidae – Cassidinae, Eumolpinae and Galerucinae – in the dry tropical forests of Nicaragua; and (2) infer these species' diet using molecular forensic tools. Total DNA was extracted from 371 specimens of Cassidinae, 251 of Eumolpinae, and 632 of Galerucinae, collected in 14 dry forest areas distributed along de Pacific Coast of Nicaragua. For animal species delimitation, we used phylogenies of the cox1 mito - chondrial gene and the Generalized Mixed Yule Coalescent model to establish independent evolutionary lineages, which we validated by comparison with morphospecies designations. Inference of food plant associations was obtained by amplifying the chloroplastic psbA-trnH intergenic spacer from plant tissue remains in the beetle DNA extraction and each sequence was contrasted with GenBank data and our own reference database using the BLAST algorithm and phylogenetic methods. For Cassidinae we obtained 79 species and 388 food inferences that correspond to 35 botanical families, for Eumolpinae we obtained 51 species and some 130 food associations in 21 plant families; finally, for the Galerucinae, we obtained 194 species and 310 diet sequences that correspond to 40 botanical families. These data allowed us to evalu- ate aspects on the biodiversity of interactions of beetle and plant communities, including the degree of trophic specialization of each beetle assemblage, diet overlap among beetle groups, and seasonal or local ecological adaptations. This study, with relatively low cost and time effort has generated a lot of valuable and novel information about the diversity of herbivore beetles and their interactions with host plants in the dry tropical forest. In the future, we hope that this approach will allow us to understand the ecological niche of these species and their role in the food-web structure of this highly threatened ecosystem.