Mémoire
| Résumé : | Spotted eagle rays are large semi-pelagic organisms. Historically considered a single circumtropically distributed species, molecular analyses have highlighted the need for a taxonomical re-evaluation of this group, which now comprises three described species.Phylogenetic analyses have identified various barriers to gene flow, paving the way for biogeographic inferences regarding the reasons for the sundering of ancestral lineages.The present study set out to evaluate the level to which present-day spotted eagle ray populations are structured, to apply standard delimitation methods to this species complex and to retrace its biogeography. To meet these goals, I gathered all the available molecular data deposited in online databases (all of which were from mitochondrial genome regions) and reanalysed them.My findings show that Indo-Pacific populations are genetically structured, which may be evidence for several cryptic species occurring in this region or could represent a signature of maternal philopatry. A Tethyan centre of origin is suggested for the Aetobatidae family. An additional evolutionary process (i.e. vicariance or dispersal) is detected between Indo-Pacific and New World populations, supporting the possible presence of a cryptic species of spotted eagle ray in the Eastern Atlantic basin.Although some interesting new patterns were detected in this study, they were all based on available mitochondrial sequence data that will need to be compared to independent, nuclear datasets in order to test for reproductive connectivity and to decide between the competing hypotheses of maternal philopatry or the presence of yet undetected cryptic species.Particularly important for this purpose will be targeted sampling efforts aimed at the western coast of Africa in order to find out whether distinct populations of spotted eagle ray may occur there. |
