Morphometric variation between two morphotypes within the Astyanax Baird and Girard, 1854 (Actinopterygii: Characidae) genus, from a Mexican tropical lake.
Phenotypic variation is important for evolutionary processes because it can allow local adaptation, promote genetic segregation, and ultimately give rise to speciation. Lacustrine systems provide a unique opportunity to study the mechanisms by which sister species can co-occur by means of ecological segregation. The fish genus Astyanax is characterized by high levels of phenotypic variability, providing an excellent model for the study of local specialization. Here, we analyze the morphological specializations through geometric morphometrics of two sympatric species described as different genera: Bramocharax caballeroi endemic to Lake Catemaco, and the widely distributed Astyanax aeneus. Additionally, we assess the correlation between phenotypic and genetic structure, and the phylogenetic signal of morphological variation. We examined body size and shape variation in 196 individuals and analyzed mitochondrial cytochrome b sequences in 298 individuals. Our results confirm the striking morphological divergence among the sympatric characids. Differences between them were mainly found in the body depth and profile and orientation of the head, where B. caballeroi in contrast with the A. aeneus, presented a fusiform body and an upward mouth. Moreover, different growth trajectories were observed among morphotypes, suggesting that a heterochronic process could be involved in the diversification of our study system. Morphological differences did not correspond with the molecular differentiation, suggesting high levels of homoplasy among the lineages of B. caballeroi morphs.
Departamento de Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006, Madrid, Spain; Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Mexico.
Claudia P
CP
Ornelas-García
Markus
M
Bastir
Ignacio
I
Doadrio
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D049628:Body Size; D060126:Characidae / Q000033:anatomy & histology* / Q000145:classification / Q000235:genetics; D045303:Cytochromes b / Q000235:genetics; D029941:Fish Proteins / Q000235:genetics; D014644:Genetic Variation; D006239:Haplotypes; D060106:Lakes; D008800:Mexico; D058889:Molecular Typing; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013045:Species Specificity
D029941:Fish Proteins; D045303:Cytochromes b
homoplasies; lacustrine; mitochondrial DNA; morphology; trophy