Role of morphology in shaping the feeding niche of fishes inhabiting Eastern Himalayan torrential rivers of West Bengal, India

Abstract

Ecomorphology and trophic ecology are considered important features in comprehending the feeding structure of fish communities. This study assesses the ecomorphological relationships among 45 fish species inhabiting the Eastern Himalayan torrential rivers, Murti and Jaldhaka by identifying morphological and trophic associations highlighted by prey acquisition strategies and the potential phylogenetic convergence among morphological traits. Two approaches (3‐guild and 5‐guild) were employed for evaluating the prediction accuracy of morphology in classifying the guilds. While the former was based on “troph” (dietary index) values, the later focussed on diet dissimilarity matrix. In terms of phylogenetic relatedness, traits such as caudal peduncle aspect ratio and mouth protrusion showed prominent phylogenetic signal which suggested their evolutionary convergence in certain groups. Subsequent modelling suggested that while linear discriminant model showed morphological traits to have higher accuracy (91.1%) in classifying the three guilds as compared to five guilds (72.31%), redundancy model (explaining 85.26% constrained variance) revealed a morphological association with specific prey type selection. Additionally, linear models showed substantial variation (93.72%) in the dietary index being addressed by the 5‐guild classification as compared to the 3‐guild (79.72%). Results suggested that in terms of prey composition or selectivity, the 5‐guild model was more suited in representing the feeding structure while the morphological traits reflected a broader scheme of classification (3‐guild model). Hence, this provides an ecological insight into the different modes of resource utilisation by the coexisting species which are being expressed in their differentiating morphologies, with certain traits being phylogenetically conserved within specific feeding groups.