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

Abstract

Based on geometric morphometrics and discriminant analysis, the percentage of silverside Odontesthes hatcheri and Odontesthes bonariensis individuals identified 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 to environmental cues such as 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.

Populations of Odontesthes (Teleostei: Atheriniformes) in the Andean region of Southern South America: body shape and hybrid individuals

“…In agreement with Crichigno et al (2013) (Liotta, 2006). The Ezequiel Ramos Mexía reservoir, three reservoirs used for this study (NIHL, CDP, and AME), and one lake (URRE) included both species, but did not yield intermediate forms as in PELE.…”

“…Lake Pellegrini. In consequence, and in agreement with the results of Crichigno et al (2013), even lakes and reservoirs with water temperature too low for O. bonariensis could have received lowtemperature-resistant hybrid and / or introgressed individuals, resulting in O. hatcheri populations with high morphological variation. There, taxonomically assigned O. hatcheri individuals could have a low probability of being classified as O. hatcheri in geometric morphometric analysis (Fig.…”

“…In particular, morphological variation within O. hatcheri involves body height and the relative positions of the anus, pelvic and anal fins. In agreement with Aigo et al (2008), who positively relate abundance of O. hatcheri to the area of the lake, and the dependence of cephalic shape of O. hatcheri on coastline development (Crichigno et al, 2013), significant relationships between DFs and independent variables affecting quality and quantity of planktonic food availability (TP and altitude) were observed. Part of this variation could be ascribed to phenotypic plasticity (Crichigno et al, 2012).…”

“…In consequence, brood stocks were never established in Argentina before 2001, when Somoza et al (2008) implemented spontaneous spawning of O. bonariensis in captivity. Thus, the southernmost hatchery (Piscicultura Río Limay) participating since 1930 in 'pejerrey' stocking programs throughout the Andean Cuyan and Patagonian Provinces (Crichigno et al, 2013) always stocked fish obtained from adults caught in neighboring sites, e.g. Lake Pellegrini.…”

“…1) has been subject to stocking practices, with Odontesthes bonariensis (Valenciennes, 1835) stocking carried out by three hatcheries (Estación Hidrobiológica de Chascomús 35º36'S, 58º01'W, Estación de Piscicultura de Embalse 32º13'S, 64º29'W, and Estación de Piscicultura Río Limay 38º59'S, 68º14'W) since 1930 (Dyer, 2006;Crichigno et al, 2013). Crichigno et al (2013) differentiated O. hatcheri, O. bonariensis and intermediate individuals on the basis of head shape. The taxonomic categories included a non-negligible number of individuals considered misclassified cases.…”