Speaker
Description
Speciation encompasses genetic and phenotypic divergence, and the establishment of reproductive isolation, facilitating the coexistence of nascent species. However, some species, termed cryptic species, lack discernible morphological differences but maintain reproductive isolation through behavioral traits. These cryptic species may evade detection by visually oriented scientists, posing challenges for taxonomy and conservation. Understanding cryptic morphological traits and their relationship with behavioral signals is crucial for delineating genetic differentiation between hybridizing species. The Chorthippus biguttulus complex in the Alps offers an ideal system to explore the role of morphological traits in nonecological speciation. Despite minimal ecological differentiation over 1.4 million years, reproductive isolation is strong within this complex due to coupling of multiple barriers like courtship song and cuticular hydrocarbons. However, the existence of a putative hybrid, C. brunneus ab. ticino, is an exception that occurs at high elevation in the Alps and shows an intermediate courtship song between C. brunneus and C. biguttulus. Our study aimed to determine: 1) the morphological traits correlated with divergent songs that aid in species distinction, and 2) whether these morphological characters evolve neutrally within the phylogenetic context and genomic background. Using three morphometric approaches and incorporating population-level sampling, we assessed wing morphological differentiation among five taxa. Despite significant intraspecific variation, linear discriminant analysis effectively separated taxa based on wing morphology, primarily involving wing width and length. Our findings indicate that wing morphology mirrors the patterns observed in courtship songs, with discrepancies with genomic data, suggesting non-neutral evolution. Furthermore, the putative hybrid exhibited intermediate wing morphology. These results do not only underscore the utility of morphological traits as proxies for behavioral traits but also highlight the potential for geometric morphometric approaches to detect cryptic species efficiently in future high- throughput analyses. This study has broader implications for taxonomy, conservation, and the scalability of morphometric approaches in biodiversity research.
