Among skates, Rajidae represents one of the most enigmatic family of cartilaginous fish whose bio- ecological traits contributed to an extraordinary evolutionary success in terms of species richness and endemism. Past and present taxonomic conflicts and species misidentifications are linked to their extraordinary level of morphological stasis. In recent years, these issues have been overcome by wide- scale molecular taxonomy analyses, but also raised questions about their evolutionary history. Concerted actions as the ELASMOMED and ELASMOATL initiatives encouraged and improved large-scale sampling efforts in the Mediterranean and Eastern Atlantic Ocean over years, building unique voucher repositories of thousands of specimens and enabling the exploration of skates’ biogeography. Here, the maximum taxonomic (51 OTUs) and molecular (47 OTUs) diversity of tribes Rajini and Amblyrajini were measured using concatenated mitochondrial genes. We also estimated their evolutionary divergence using the molecular clock approach. Evidences produced so far showed that, despite the ancient origin of Rajidae (97 MYA), the Eastern Atlantic and Mediterranean faunas originated more recently, after the closure of connection between these areas and the Indo-Pacific Ocean (15 MYA). The endemic Mediterranean species originated with the recolonization of the Basin, after the Messinian salinity crisis (7-5 MYA). At least five independent vicariant events contributed from 7.4 to 3.15 MYA to the formation of allopatric or parapatric sister species, each distributed in the N-E Atlantic and S-E Atlantic respectively. On the whole, the Quaternary tectonic movement of continental masses, paleoclimatic events and present oceanographic discontinuities occurring along the western African continental shelf might explain this series of parallel and independent speciation events related to the maintenance of low or null levels of gene flow between closely related sibling and cryptic species.
Step by step: the unprecedented evolutionary history of family Rajidae
Alice Ferrari;CROBE, VALENTINA;Alessia Cariani;Fausto Tinti
2019
Abstract
Among skates, Rajidae represents one of the most enigmatic family of cartilaginous fish whose bio- ecological traits contributed to an extraordinary evolutionary success in terms of species richness and endemism. Past and present taxonomic conflicts and species misidentifications are linked to their extraordinary level of morphological stasis. In recent years, these issues have been overcome by wide- scale molecular taxonomy analyses, but also raised questions about their evolutionary history. Concerted actions as the ELASMOMED and ELASMOATL initiatives encouraged and improved large-scale sampling efforts in the Mediterranean and Eastern Atlantic Ocean over years, building unique voucher repositories of thousands of specimens and enabling the exploration of skates’ biogeography. Here, the maximum taxonomic (51 OTUs) and molecular (47 OTUs) diversity of tribes Rajini and Amblyrajini were measured using concatenated mitochondrial genes. We also estimated their evolutionary divergence using the molecular clock approach. Evidences produced so far showed that, despite the ancient origin of Rajidae (97 MYA), the Eastern Atlantic and Mediterranean faunas originated more recently, after the closure of connection between these areas and the Indo-Pacific Ocean (15 MYA). The endemic Mediterranean species originated with the recolonization of the Basin, after the Messinian salinity crisis (7-5 MYA). At least five independent vicariant events contributed from 7.4 to 3.15 MYA to the formation of allopatric or parapatric sister species, each distributed in the N-E Atlantic and S-E Atlantic respectively. On the whole, the Quaternary tectonic movement of continental masses, paleoclimatic events and present oceanographic discontinuities occurring along the western African continental shelf might explain this series of parallel and independent speciation events related to the maintenance of low or null levels of gene flow between closely related sibling and cryptic species.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
