Avis de Soutenance
Thomas AUBIER
Soutiendra publiquement ses travaux de thèse intitulés
Diversity of warning signals, speciation and clade diversification
Soutenance prévue le vendredi 14 septembre à 14h
Lieu : l'Amphithéâtre de la Délégation Languedoc-Roussillon du CNRS

The display of warning signals by unpalatable (or otherwise defended) prey provides a wonderful opportunity for estab-lishing an integrative view of biological diversification. Warning signals are known to be under strong natural and sexual selection. On the one hand, the sampling strategy of predators, characterized by a learned avoidance of signals associated with unpalatability, generates natural selection in favour of warning signals in high frequency in the prey community. Such positive frequency-dependent selection favours phenotypic uniformity and causes unpalatable species to converge on common warning signals (mutualistic "Müllerian" mimicry), as seen in a large panel of taxa. On the other hand, warning signals are used as a phenotypic cue for mate choice, generating sexual selection with important consequences for repro-ductive isolation and speciation.

Paradoxically, despite powerful selection favouring phenotypic convergence, warning signals are fantastically diverse, both within and between species, and this morphological diversification is often associated with extensive species diversification at the clade level. In this thesis, I tackle this apparent paradox from the ground up and I thereby refine our understanding of the role of positive frequency-dependent selection and mutualistic interactions for evolutionary diversification at micro- and macroevolutionary scales. First, I show that the predator sampling strategy can favour the emergence of diversity of warning signals despite positive frequency-dependent selection. Second, I dissect the conditions allowing the evolution of strong and stable reproductive isolation, necessary for speciation to occur, in a number of ecological situations where warning signals are under natural and sexual selection. Third, I highlight important indirect effects of frequency-dependent selection on diversification at macro-evolutionary scale via spatial constraints and by-product ecological convergence.

Keywords: frequency-dependent selection, mutualism, predator cognition, speciation, clade diversification, theory

Membres du jury:

M. Michael KOPP         Aix Marseille Université - CNRS UMR 7373 (I2M)         Rapporteur
M. Christophe THÉBAUD          Université Paul Sabatier - CNRS UMR 5174 (EDB)         Rapporteur
Mme Emmanuelle PORCHER          Museum National d'Histoire Naturelle - CNRS UMR 7204 (CESCO)         Examinatrice
Mme Carole SMADJA          Université de Montpellier - CNRS UMR 5554 (ISEM)         Examinatrice
M. Mathieu JORON         Centre d'Ecologie Fonctionnelle et Evolutive - CNRS UMR 5175         Directeur de these
Mme Marianne ELIAS          Museum National d'Histoire Naturelle - CNRS UMR 7205 (ISYEB)         Co-directrice de these