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Hybrid speciation in a marine mammal: the Clymene dolphin (Stenella clymene)
Amaral, Ana Rita1, 2; Coelho, Maria Manuela1; Amato, George2; Rosenbaum, Howard C3, 2
(1) Centro de Biologia Ambiental, Faculdade de Ciências da Universidade de Lisboa, Edifício C2, 3ºpiso, Lab., Campo Grande, Lisboa, 1749-016, Portugal
(2) Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th street, New York, New York, 10024, USA
(3) Ocean Giants Program, Wildlife Conservation Society, 2300 Southern Blvd, Bronx, New York, 10460, USA
Corresponding author: aramaral@fc.ul.pt
Natural hybridization may result in the exchange of genetic material between divergent lineages and even the formation of new taxa. Many of the Neo-Darwinian architects argued that, particularly for animal clades, natural hybridization was maladaptive. Recent evidence, however, has falsified this hypothesis, instead indicating that this process may lead to increased biodiversity through the formation of new species. Although such cases of hybrid speciation have been described in plants, fish and insects, they are considered exceptionally rare in mammals. Here we present evidence for a marine mammal species, Stenella clymene, arising through natural hybridization. We sequenced one mitochondrial and six nuclear DNA regions from specimens across the geographic distribution of Stenella coeruleoalba, Stenella longirostris and S. clymene. We found phylogenetic discordance between mitochondrial and nuclear markers. This finding, coupled with a pattern of transgressive segregation seen in the morphometric variation of some characters, support a case of hybrid speciation. S. clymene is currently genetically differentiated from its putative parental species, S. coerueloalba and S. longisrostris, although low levels of introgressive hybridization may be occurring. Our results demonstrate that hybrid speciation has contributed to the biodiversity of marine mammals. We anticipate that our study will bring attention to this important aspect of reticulate evolution in marine mammal species, which can have critical consequences for its conservation and management.