Morphological and Genetic Divergence of Hoplias microlepis (Characiformes: Erythrinidae) in Rivers and Artificial Impoundments of Western Ecuador
Little is known about the freshwater fishes of western Ecuador despite serious environmental threats, including the creation of large artificial impoundments. Phenotypic and genetic divergence of populations of a large predatory fish, Hoplias microlepis, is examined in rivers and artificial impoundments of the Guayas River drainage in western Ecuador. Despite the recent formation of the impoundments (∼20 years prior to the sampling), H. microlepis in these habitats diverged morphologically from river populations. Impoundment fish tended to have larger eyes, longer dorsal and caudal fins, and thinner bodies than river fish. Classification rates for habitat of origin based on morphometric measures were relatively high (71.7–83.3%), and the magnitude of morphological divergence was substantial when contrasted with divergence from H. malabaricus, a congener from eastern Ecuador. Frequencies of mtDNA d-loop haplotypes differed significantly among samples. Genetic divergence between river samples implies that the genetic structure in the drainage predates the formation of the impoundments. The genetic analysis also indicates that the morphological divergence between fish in different habitat types is not likely due to shared ancestry. Genetic diversity tended to be higher in the river samples, and the percentage of private alleles was higher in the impoundment populations, which is consistent with rapid population expansion from a limited number of founders in impoundments.
Collection sites for Hoplias microlepis. Inset indicates position of Guayas River drainage in western Ecuador. Symbols indicate the four collection sites: two artificial impoundments, Daule-Peripa and Chongon; and two river sites, Quevedo River and Babahoyo River. Guayaquil indicates the position of the city of Guayaquil, and Daule River and Babahoyo River indicate the two major tributaries forming the Guayas River. Scale bar is 20 km.
Morphometric analysis of samples of H. microlepis and H. malabaricus. (A) Principal component analysis (PCA) of all samples indicating the distribution of the samples along the two major axes of body shape variation. Percentages are the amount of shape variation accounted for by each PC. Inset shows sample means, and error bars are 95% confidence intervals of the mean. (B) Discriminant Function Analysis (DFA) of river H. microlepis, impoundment H. microlepis, and Amazonian H. malabaricus. (C) DFA of river and impoundment H. microlepis. DF2 is plotted against standard length to highlight morphological divergence among river and impoundment H. microlepis in relation to body size.
Haplotype network constructed using Network 4.5.1.6. Panels A–D are close-ups of haplotype classes A–D, modified to facilitate visualization. Haplotype classes are defined based on the presence of a tandemly repeating 34 bp insert and differ by having 0, 1, 2, and 3 tandemly repeated inserts, respectively. For convenience, each of these haplotype classes was assumed to have a single evolutionary origin, which provided a convenient classification of haplotypes. Shading indicates haplotype frequencies in each population. The size of the circles is proportional to haplotype frequencies. (E) Complete haplotype network.
Contributor Notes
Associate Editor: D. Buth.