Development as a driver or a brake of morphological diversity?

The majority of animals, including the most successful and speciose groups of insects (over 80%) and vertebrates (more than one half of their known diversity or ~20,000 species), undergo metamorphosis implying drastic morphological, functional and ecological changes during the life of an organism. Thus, indirect development (i.e. biphasic) with a complex life cycle is a dominant developmental strategy and has resulted in much of the exceptional diversity that is evident today.

Metamorphosis is consequently a widespread phenomenon and may be an important driver of biodiversity, a hitherto largely neglected question which I propose to investigate in this keynote. Salamanders are an excellent model to do so, as they are sensitive ecological indicators, highly diverse (~800 species) and show the largest variation in life cycle types among vertebrates.  The conceptual framework offered by the presence of a diversity of life cycles allow us to test the ability of an organism to adapt to environmental changes by producing morphological variation (larval and adult stages) from a single genome.

As such, we quantitatively analyse the role of development and function on the evolution of phenotypic diversity on the feeding system over evolutionary timescales, using a comparative approach combining different taxonomic and ontogenetic scales. To do so, we use interdisciplinary approaches combining functional morphology, developmental biology, diversification analyses and statistical modelling to disentangle the factors driving diversity at different ontogenetic stages across space and time.

Our results show that life cycle complexity can, depending on the anatomical structure, constrain or alternatively facilitate the evolution of morphological structures and their diversity. As such life cycle complexity can strongly impact the pattern of morphological diversification across species. Furthermore, the changes encountered during life cycle shifts have, in some cases, facilitated divergent evolutionary dynamics between species and the colonization of new habitats.

This presentation will shed light on whether life cycle variation has played a major role in the morphological and functional diversity of salamanders.