The evolutionary history of Caridina typus: phylogeography, species delimitation and an analysis of the complexity of the Indo-Pacific biogeography

Abstract

The Indian Ocean comprises nine hotspots of biodiversity in its area of influence, including some of the worlds most iconic (and thus most studied) centres of endemism. Historically, the area serves as a prolific laboratory for geologic and biogeographic studies and by assessing the biodiversity distribution it became possible to infer about the biological history of the region and the processes that influence it, particularly in what refers to endemism. The study of non-marine species widely distributed across the Indian Ocean such as Caridina typus H. Milne-Edwards, 1837 may shed some light on many of these dilemmas on the recent history of this area and of the evolutionary dynamics of vagile species. The primary objective of this study is, therefore, the investigation of the evolutionary history of the C. typus populations and to canvass their relations and taxonomic status. Five molecular markers were amplified (two mitochondrial and three nuclear) for 129 individuals across the Indo-Pacific region (species area of occurrence). Caridina typus dated phylogeny can be found in chapter 3 with an inference of the evolutionary history of the species complex. Still in chapter 3, three species were suggested by delimitation methods in C. typus by three different methods. By showing, for the first time in literature, an agreement between various methods, a brief critique on the species delimitation based on mitochondrial markers was also made. Based on the theoretical scenario in which this research is inserted, a second aim was established: a review and metaanalysis of the biogeographical molecular studies done across the Indian Ocean. That ocean has a complex geological history, intimately related to the fragmentation of supercontinentes, paleo-oceans and the Indias drift through the hemispheres. However, biogeographic estudies there have been more influenced by biogeographic schools than by real evidence from biodiversity. With the new methods associated to the development of the molecular biology one can elucidate a great part of the discussions on Indian Oceans areas of endemism. In chapter 2 (organised this way due to practical reasons), the literature about the geological and biological history of the region was extensively reviewed and 7 phylogenetic works more or less geographically inclusive were re-analysed. The results show that the biogeographic history of the region is complex and involves various events of vicariance, dispersal (both short and long-distance) and that the area still has much to offer in terms of knowledge on evolutionary processes