Abstract
During a survey of genetic and species diversity patterns of leaf beetle (Coleoptera: Chrysomelidae) assemblages across the Iberian Peninsula we found a broad congruence between morphologically delimited species and variation in the cytochrome oxidase (cox1) gene. However, one species pair each in the genera Longitarsus Berthold and Pachybrachis Chevrolat was inseparable using molecular methods, whereas diagnostic morphological characters (including male or female genitalia) unequivocally separated the named species. Parsimony haplotype networks and maximum likelihood trees built from cox1 showed high genetic structure within each species pair, but no correlation with the morphological types and neither with geographic distributions. This contrasted with all analysed congeneric species, which were recovered as monophyletic. A limited number of specimens were sequenced for the nuclear 18S rRNA gene, which showed no or very limited variation within the species pair and no separation of morphological types. These results suggest that processes of lineage sorting for either group are lagging behind the clear morphological and presumably reproductive separation. In the Iberian chrysomelids, incongruence between DNA-based and morphological delimitations is a rare exception, but the discovery of these species pairs may be useful as an evolutionary model for studying the process of speciation in this ecological and geographical setting. In addition, the study of biodiversity patterns based on DNA requires an evolutionary understanding of these incongruences and their potential causes.
Highlights
DNA sequence data have been successfully used to describe patterns of biodiversity and assemblage variation in space and time [1,2,3]
Sequence-based community analysis has the potential to speed up the systematic assessment of biodiversity patterns, even in ecological systems for which taxonomic information is very limited
The usefulness of mitochondrial community analyses for describing broad biodiversity patterns is dependent on a close match between morphologically and genetically delimited species
Summary
DNA sequence data have been successfully used to describe patterns of biodiversity and assemblage variation in space and time [1,2,3]. Sequence-based community analysis has the potential to speed up the systematic assessment of biodiversity patterns, even in ecological systems for which taxonomic information is very limited This approach provides the possibility to test statistical patterns of diversity based on the genetic variation of mtDNA haplotypes and has been termed haplotype-based macroecology [3]. Geographic differentiation may confound the recognition of species boundaries if intra-specific variation is high due to comparatively ancient biogeographic subdivision relative to speciation events [14,15] This latter phenomenon in particular affects the performance of methods for species recognition based on sequence divergence, since the difference between the amount of intra- and interspecific divergences (i.e. the ‘DNA barcoding gap’) is reduced when working at large geographic scales [16]
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