Habitat-Associated Morphological Divergence of Gasterosteus aculeatus in the Southern Caspian Sea Basin

Abstract

Habitat-associated morphological divergence of the three-spined stickleback, Gasterosteus aculeatus populations was investigated in the southern Caspian Sea basin using landmark-based geometric morphometric method to understand the population structure of this invasive species. A total of 127 specimens were collected from three stations, including the Babol River estuary (center), Gomishan Wetland (east) and the Gisum Coast (west). The left side of each specimen was photographed and 23 landmarks-points were selected to extract body shape data. After generalized procrustes, the data analysis was analyzed using principal components analysis, multivariate analysis of variance/canonical variate analysis and cluster analysis. The results showed a significant difference in body shape between three studied populations (P < 0.001), that were related to the depth and length of the head, the body and caudal peduncle and the positions of the pectoral and ventral fins. Morphological differences of the studied populations can be considered as response to environmental characteristics of their habitats, showing G. aculeatus as a highly successful exotic species to expand its distribution area in the Caspian Sea.