Cephalic morphological variation in freshwater silversides, Odontesthes hatcheri and Odontesthes bonariensis in Patagonia: introgression and ecological relationships

Formerly, Odontesthes hatcheri (Eigenmann) was present in Cuyo and Patagonia. The area was repeatedly stocked with Odontesthes bonariensis (Valenciennes) during the 1930s. In a recent survey, O. bonariensis individuals were captured mostly in northern localities whereas O. hatcheri ones were captured in the south. Based on Geometric Morphometrics and Discriminant Analysis, the percentage of O. hatcheri and O. bonariensis individuals indentified by a taxonomic key and misclassified by Discriminant Analysis was obtained and a negative correlation between the percentage of misclassified individuals of O. hatcheri and the distance to the nearest hatchery stocking silversides was found, suggesting a genetic introgression. Morphological analyses between species, between populations, and within populations pointed to the same anatomical structures, suggesting a nested variation related with environmental cues like availability of littoral shelter. The dependence between the cephalic morphology of O. hatcheri and body size would be in agreement with the trophic niche shifts of the species. Introgression adds a new threat to the already observed decline of populations of O. hatcheri and suggests that this species deserves particular consideration in terms of conservation guidelines.Fil: Crichigno, Sonia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; ArgentinaFil: Conte-grand, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; ArgentinaFil: Battini, M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; ArgentinaFil: Cussac, Victor Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentin