Signals of hybridization in the Trimerotropis pallidipennis complex of Andean grasshoppers

The Trimerotropis pallidipennis complex, comprising species such as Trimerotropis andeana, Trimerotropis ochraceipennis, and Trimerotropis sp., is a group of Andean grasshoppers that presents challenges in species delimitation and shows signs of hybridization events. Climate change and Andean landscape fluctuations may have facilitated hybridization between phylogenetically related species.

The difficulty in clearly defining species within this group and the absence of clear morphological differentiation suggest the possibility of hybridization among closely related species. Using RAD-seq loci markers, individuals from various lineages in southern South America were analyzed. The PhyloNetworks, Treemix, and fastsimcoal programs were employed to detect hybridization events and estimate the proportion of genes inherited by hybrid nodes.

The analysis revealed the presence of more than one hybrid event within this complex. One hybrid event occurred from Trimerotropis andeana to Trimerotropis ochraceipennis, and another was detected between populations from Mendoza, San Luis, and La Rioja with the Uspallata population of Trimerotropis sp. This study provides insights into the interactions between related species in the context of climate and geological changes in the Andes and it will contribute to understanding the mechanisms of speciation and adaptation in mountainous environments, with implications for conservation and biogeography in the Andean region.