PhD Defense - Isabelle Deregnaucourt

Disparity, an unified metric to compare the responses of biodiversity to past and current crises : a test with dragonfly wings

Thèse de doctorat sous la direction de Romain Juliard et de Loïc Villier.

Composition du jury :

• ‌M. Luc Abbadie Professeur, Sorbonne Université, Examinateur
• M. Alexander Blanke, Professeur, Universität Bonn, Rapporteur
• Mme Carolin Haug, Research associate, Ludwig-Maximilians-Universität München, Rapporteur
• M. Adrien Perrard, Maître de conférences, Université Paris-Diderot, Examinateur
• M. Jérémie Bardin, Ingénieur d’études, Sorbonne Université, Co-encadrant
• M. Olivier Béthoux, Maître de conférences, Muséum National d’Histoire Naturelle, Co-encadrant
• M. Romain Julliard, Directeur de Recherche, Muséum National d’Histoire Naturelle, Co-directeur
• M. Loïc Villier, Professeur, Sorbonne Université, Co-directeur

Abstract :

Organisms through time have been strongly affected by five major crises and human activities are leading to a sixth one. It is difficult to compare these extinctions using species richness, due, in part, to sampling biases. Disparity, aiming at quantifying morphological diversity, might be a relevant approach. The contrast between morphological and taxonomic diversity has been used to address properties of extinction events in the fossil record. Disparity has, however, rarely been applied in conservation biology. Here we investigated the impact on Odonata wing disparity (1) of land cover artificialization and (2) of the Permo-Triassic mass extinction. To quantify wing morphology, we assessed a basic pattern of wing venation homologies applicable to extant and fossil species. We then used a morphometric geometric approach and elaborated an optimal set of landmarks and sliding semi-landmarks. Impact of artificialization has been investigated on sites in Ile-de-France. Artificialization and loss of species do not significantly impact disparity. This support a scenario of a non-morphologically selective extinction. We did not found evidence that wing morphology might help recognition of specialized or generalist species. No significant differences between disparity and diversity of the Permian and the Triassic were observed. Extreme morphologies lost in the Permian may have been compensated with new extreme morphologies during the Triassic. Given the temporal resolution, effects of species loss and recovery cannot be distinguished. Current crises could be comparable in their effects to past mass extinction. However, data on extant should be broadened to all the species monitored worldwide and resolution of fossil sampling refined.