EMEC_2023_00132 - Maravillas larvarias: patrones y mecanis

A continuing challenge in evolutionary biology is to fully understand how novel phenotypes arise, how phenotypic diversity is propagated across the tree of life and how this is linked to the evolution of species. Selection is expected to shape the morphology of organisms, who over time become optimized for their environment. However, the majority of animals have complex life-cycles that contain one or more morphologically and ecologically distinct phases. Selection is therefore expected to exert different, ontogeny-specific pressures, presenting situations of conflict between selection and developmental constraints. This interplay is not fully understood. This is an important knowledge gap because larval forms are common in vertebrates, especially in amphibians, whose tadpoles bear a number of highly specialized traits that are completely lost at metamorphosis. In frogs and toads especially, the entire body plan is reconfigured at metamorphosis, including the complete absorption of the tail and restructuring of the head and feeding apparatus. These therefore are interesting, transient phenotypic characters, that are only under selection during a single phase in the life-cycle. Their true diversity, to what extent they reach adaptive optima or are developmentally constraint, and whether the emergence of novel or composite traits contribute to lineage diversification is not at all understood. Moreover, what the gene regulatory networks underlying these features are, has not been extensively explored. This project seeks to address these shortcomings, by combining taxonomically-comprehensive comparative phylogenetic analyses, with targeted, cutting-edge spatial transcriptomics, and computational fluid dynamics. This project will produce the most complete understanding of both the patterns and mechanisms by which transient states evolve for any major vertebrate group to date. The evolution of tadpole phenotypes for more than 3000 species of frogs and toads (the current estimate of known Anura larval forms) will be studied, to quantify, to the fullest extent, their morphological diversity. Body shape will be quantified at high resolution using geometric morphometrics and the morphologically complex and composite-trait oral discs will be analysed using deep learning and computer vision. On a subset of species representative of the entire morphospace, we will use three-dimensional surface models and spatial transcriptomics to glean insights into the functional significance of specific morphological traits in diverse ecological contexts, and gene expression patterns and regulatory pathways driving morphological diversity in tadpoles. This combination of a largescale, amphibia-wide study with a targeted morphotype-specific focus will have an important impact on the current state-of-the-art of the adaptation of transient states.