CheliceLand · Molecular palaeobiology and comparative genomics of chelicerate terrestrialisation

Molecular palaeobiology and comparative genomics of chelicerate terrestrialisation

What is the problem being addressed? Animals have marine origins and only four lineages have adapted to life on land. These groups are the vertebrates (e.g. reptiles, mammals), molluscs (e.g. land snails, slugs), the onychophora (velvet worms) and the arthropods (e.g. insects, spiders). The water-to-land transition is referred as terrestrialisation, and is an extreme case of adaptation to a new environment. My research has been focused on the arthropod lineage, and I have been interested in knowing 'how' and 'when' these organisms have colonised the land. I am particularly interested in the comparative genomics of one of the groups that conform it, the chelicerates (e.g. spiders, scorpions, mites). Chelicerates contains marine and land representatives as well as abundant terrestrial fossil record. I combined the genomic and fossil information of these organisms to study the modifications that allowed marine chelicerates to adapt to life on land. Why is it important for society? This action is a blue skies project, however, studying the most extreme case of habitat colonization (i.e. invasion) can help understanding the biology of current invasive species, like the pest Drosophila suzukii – the containment of which is a EU priority. Chelicerates include pests (e.g. the spider mites) and species of biomedical relevance (e.g. the ticks – vectors of lyme disease). By identifying chelicerate–specific genomic adaptation to life on land, this project could potentially identify potential chelicerate–specific drug targets which may help the development of lineage–specific pesticides with low incidence on economically important arthropods, like the declining bees. What are the overall objectives? Two objectives have been set at the beginning of this action: (1) To resolve and date the chelicerate radiation, estimate how many times the chelicerates colonised the land, and test whether their terrestrial diversification was a continuous or discontinuous (i.e. punctuated by diversification bursts and biotic crises) process. (2) To identify the genes that underwent adaptive changes when chelicerates adapted to life on land. Conclusions of the action - The terrestrial chelicerates, Arachnida, have colonised the land just once. - The colonisation of land happened during the Cambrian-Ordovician. - The terrestrial diversification was marked by an initial explosive cladogenesis, giving origin to most of the extant arachnid orders. - The fast and ancient diversification that took place during the origin of Arachnida, makes difficult the identification and interpretation of the adaptive changes to terrestrial environments that experienced this lineage.

Data: CORDIS, © European Union