title: Sex beyond species: the first genetically analyzed case of intergeneric fertile hybridization in pinnipeds.
abstract: A species, according to the biological concept, is a natural group of potentially interbreeding individuals isolated by diverse mechanisms. Hybridization is considered the production of offspring resulting from the interbreeding of two genetically distinct taxa. It has been documented in over 10% of wild animals, and at least in 34 cases for Artic marine mammals. In Otariids, intergeneric hybridization has been reported though neither confirming it through genetic analyses nor presenting evidence of fertile offspring. In this study, we report the finding of a hybrid adult female between a South American fur seal (Arctocephalus australis) and a South American sea lion (Otaria byronia), and its offspring, a male pup, in Uruguay. Further based on morphological constraints and breeding seasons, sex-biased hybridization between the two species is hypothesized. Morphological and genetic (nuclear and mitochondrial) results confirm de hybrid nature of the female-pup pair. Here we discuss a genetic dilution effect, considering other hybridization events must be occurring, and how isolation mechanisms could be circumvented. Moreover, the results obtained from stable isotope analysis suggest feeding habits may be a trait transmitted maternally, leading to consider broader issues regarding hybridization as an evolutionary innovation phenomenon.
authors.affiliation: Departamento de Ecología & Evolución, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay.
authors.forename: Valentina
authors.initials: V
authors.lastname: Franco-Trecu
authors.affiliation: Departamento de Ecología & Evolución, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay.
authors.forename: Carolina
authors.initials: C
authors.lastname: Abud
authors.affiliation: Departamento de Ecología & Evolución, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay.
authors.forename: Matías
authors.initials: M
authors.lastname: Feijoo
authors.affiliation: De la Raíz Films, Solano Antuña 2720/5, Montevideo 11300, Uruguay.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Kloetzer
authors.affiliation: De la Raíz Films, Solano Antuña 2720/5, Montevideo 11300, Uruguay.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Casacuberta
authors.affiliation: Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Km 103 carretera Tijuana-Ensenada, 22860 Ensenada Baja California, México.|Metric Genetic Laboratory, Sport City, Blvd Adolfo López Mateos 1181, San Pedro de Los Pinos, 01180 Ciudad de México, México.
authors.forename: Paula
authors.initials: P
authors.lastname: Costa-Urrutia
mesh_terms: D000818:Animals; D005247:Feeding Behavior; D005260:Female; D046069:Fur Seals / Q000235:genetics* / Q000502:physiology; D006824:Hybridization, Genetic; D008297:Male; D010802:Phylogeny; D046070:Sea Lions / Q000235:genetics* / Q000502:physiology