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Geometric morphometric analyses define riverine and lacustrine species-flocks of Himalayan snowtrout (Cyprinidae: Schizothorax) in Nepal

Binod Regmi*, Marlis R. Douglas, David R. Edds, Michael E. Douglas

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ABSTRACT: Schizothorax (snowtrout) are minnows (Cyprinidae) broadly distributed in Asian Region. Body shape of three Lake Rara endemic (S. macrophthalmus, S. nepalensis, S. raraensis; northwest Nepal) and two widely-distributed riverine species (S. progastus, S. richardsonii) across three drainages in Nepal (i.e., Karnali, Gandaki and Koshi rivers) were studied using geometric morphometry. Data were derived from museum vouchers/tissues collected from 1984–1986 and 1996 (Lake Rara). Cartesian coordinates of 18 anatomical points (Type I landmark) from 528 individuals were digitized, then shape variation was quantified with principal component analysis (PCA) and visualized with Thin-Plate-Splines derived from a Procrustes analysis. Models of shape variation (i.e., taxonomy versus geography) were tested with a multivariate analysis of variance (MANOVA) and a morphological distance matrix (MDM). Phylogeographic relationships were examined with a haplotype network (N=115) derived from 1,140 base-pairs of the mitochondrial (mt)DNA cytochrome b gene, and selected GenBank sequences (N=5). Koshi River snowtrout diverged morphologically from conspecifics, consistent with the phylogeographic data. In contrast, Gandaki and Karnali river snowtrout grouped by morphotype (up-versus-downstream) irrespective of geographic origin, yet clustered separately within the haplotype network. Lake Rara snowtrout were morphologically but not genetically distinct, due to incomplete lineage sorting. Morphological and genetic variability in Schizothorax from Nepal represent a mosaic driven by isolation (=vicariance) and specialization (=adaptation), with taxonomy insufficiently reflecting diversity. Additional data are required to appropriately derive management and effective conservation plans.