Radiation and diversification patterns in early jawed vertebrates

点击翻译按钮获取中文摘要

Jawed vertebrates, or gnathostomes, account for 99.8% of living vertebrate species. Living gnathostomes include some 1 270 species of cartilaginous fishes (sharks, skates, rays and chimaeras), 29 000 species of ray-finned fishes (actinopterygians) and 33 880 species of tetrapods including our own species. This exceptional diversity is the result of a 440-million-year-long history that has been accompanied by events of evolutionary radiations. Early gnathostome key innovations include the presence of jaws and teeth, paired olfactory organs, pelvic fins and girdles and intromittent reproductive organs. These anatomical novelties have provided ecological, behavioral and reproductive advantages that were presumably associated with their early adaptive radiation. Because of these novelties, Devonian (419-359 Ma) gnathostomes were cosmopolitan in distribution, lived almost exclusively in aquatic habitats, occupied the whole food web and ranged in size from 2 cm to 4 m. Over the past decade, the discovery of new fossils of jawed vertebrates, the use of new cutting-edge technologies (micro- and nano-CT scan, synchrotron X-ray microtomography) and new analytical methods have shed light on gnathostome phylogeny. The evolutionary success of gnathostomes has been attributed alternately to the origin of the key innovations, ecological or environmental shifts, or their paleogeographic distribution. However, none of these scenarios have been framed in a broad-scale phylogeny in order to test hypotheses about biotic and abiotic factors which might have triggered the radiation. Notwithstanding the paramount importance of radiations during the evolution of life, an integrative framework for evolutionary radiation hypotheses is still lacking. ******For the next 5 years, the main goal of my research program will be to document the evolutionary radiation of jawed vertebrates by identifying rapid temporal changes in terms of the number of species, rates of evolution as well as rapid divergences in morphology and ecology. All these components will be integrated into a novel phylogenetic framework in order to identify factors acting as drivers of radiations. This quest for the “when, where and how” gnathostomes originated will led to an integrative and innovative approach to studying the origin and early radiation of taxonomic groups. Using the jawed vertebrate radiation, I wish to contribute to the general theory of evolutionary radiations as well as training highly qualified personnel in evolutionary biology. Increasingly interpretation of the pastboth recent past and deep timehelps to understand the processes that generate and maintain diversity in time and space. A better understanding of evolutionary radiations and triggering factors is essential to comprehend not only past evolution but also the ongoing effects of global changes on biodiversity.