Phylogénie moléculaire et analyse morphométrique des pédicellaires et du test des Cidaroida (Echinodermata, Echinoidea)

Abstract : The last revision of the Cidaroida (Echinodermata, Echinoidea) dates back to the beginning of the 20th century (Mortensen, 1928). In this work, Mortensen stresses on the use of traits taken on the pedicellariae for classificatory purpose at every level of the taxonomy. However and in spite of Mortensen efforts to clarify the taxonomy of the Cidaroida, this group remains seldom studied (Smith et Whright, 1989). It seems therefore a necessary task to reevaluate the relevance of the morphological characters classically used in the classification of the Cidaroida. In the present study, I explore three main research axis using different exploratory methods in order to come to a better understanding of the systematics and evolutionary history of the Cidaroida. In the first part, I investigate the variation and ontogenesis of a number of morphological traits taken on the pedicellariae. In the second part, I examine the post larval growth in different population of Stylocidaris affinis. In the third part, I present the first phylogenetic reconstruction of a large sample (27 taxa) representative of the whole group, based on molecular sequences (28S-D1 and COI), using the parsimony criterion. Using a morphometric approach, I show that the observed variability in shape of the globiferous pedicallariae is explained by static allometries. I also show that the different types of pedicellariae observed on Stylocidaris affinis and Prionocidaris sp. can be interpreted in term of heterochronic processes. As a consequence I discuss the taxonomic implication of these results. The test growth is explained by growth allometry that may lead to significant morphological differences. Moreover, drastic changes in allometric patterns are shown to be related to the development of the genital pores at sexual maturity. The phylogenetic reconstruction shows the monophyly of the Cidaroida. However, the family Cidaridae is not retrieved whereas the genus Goniocidaris is well supported by both jackknife and Bremer indices.
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Olivier Brosseau. Phylogénie moléculaire et analyse morphométrique des pédicellaires et du test des Cidaroida (Echinodermata, Echinoidea). Systématique, phylogénie et taxonomie. Muséum national d'Histoire naturelle, 2005. Français. ⟨tel-02177236⟩

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