Diversification mechanisms in the Andean grasshopper genus Orotettix (Orthoptera: Acrididae): Ecological niches and evolutionary history

Abstract

The Andes harbour an outstanding taxonomic and ecological diversity, for which several mechanisms promoting diversification, including ecological gradients and allopatric speciation, have been cited. The grasshopper genus Orotettix is an informative but challenging group to study diversification mechanisms because species in the genus are morphologically very similar, have low vagility and display local endemism over a complex topography in the Central Andes. We conducted several tests using ecological niche overlap and predictions of geographical distributions of Orotettix species on a phylogenetic framework to disentangle their speciation patterns. A multilocus molecular phylogeny was generated for Orotettix. Niche similarity tests were performed and the degree of niche overlap was estimated between species. Ecological niche models were generated to assess the realized ecological niche and potential distribution. The phylogenetic signal between the phylogenetic relatedness and niche overlap, and geographical and the environmental distances were analysed. Our findings suggest that speciation was not restricted to a single period and that species origins might have coincided with glacial-interglacial cycles of the Pleistocene. Given that we only found cases of niche conservatism for Orotettix, we infer that allopatric speciation had the primary role in its diversification. No significant phylogenetic signal was found, probably due to an island-like radiation process.