Regional selection pressure and heterogeneous transitions shape diverse colour pattern in Pachyrhynchus weevils (Coleoptera: Curculionidae)

Abstract

The evolution of colouration and patterns is a captivating aspect of biological research shaped by multiple factors. Pachyrhynchus weevils, known for their unpalatable nature owing to their tough elytra, inhabit the tropical regions of the Philippines and display intricate elytral patterns that contribute significantly to species diversity. To investigate the evolution of patterns in Pachyrhynchus weevils, we used the ultraconserved elements method to construct a phylogeny encompassing 99 species and to assess pattern evolution. These weevils exhibit flexibility in pattern expression, with a trend towards pattern retention and diversification rather than pattern loss, as indicated by the analyses of evolutionary transition rates. Furthermore, using phylogenetic generalized linear regression, we found that patterns are associated with specific geographical regions, suggesting that convergent evolution of patterns occurs among weevils. Finally, our analysis revealed that speciation rates are not consistent with the rates of pattern diversification. These results highlight the complexity of pattern evolution and suggest that varying selection pressures in different areas, such as predation, combined with frequent transitions in patterns, might contribute to the evolution of these patterns, potentially leading to a rich diversity among these island-dwelling insects.