Disentangling the Taxonomy of the Mahseers (Tor spp.) of Malaysia: An Integrated Approach Using Morphology, Genetics and Historical Records

Mahseer (Tor spp.) fishes of the world: status, challenges and opportunities for conservation

“…Hora 1939), some taxonomic ambiguity remains across the Tor genus (Pinder and Raghavan 2013). Original descriptions of many mahseer species are vague and finding standard diagnostic characters to distinguish species has been difficult (Walton et al 2017). In addition, the mahseer literature of the twentieth century, particularly descriptions and illustrations available in species accounts, are inconsistent and highly variable, increasing the likelihood of misidentifications.…”

“…Published evidence on range limits has also been highly confusing and contradictory, and authentication of such information has now become impossible due to the absence of accompanying voucher specimens (cf. Walton et al 2017). The quantity of taxonomic literature is also not an indication of its quality and tends to increase confusion further (Fig.…”

“…Issues with historic and current literature on mahseer taxonomy are further exacerbated with the unique morphological variations that mahseer fishes exhibit. As a group, mahseer exhibit considerable phenotypic plasticity, including intra-specific morphological variation, trophic polymorphism, and sexual dimorphism, making precise, morphologically based identifications extremely difficult (Walton et al 2017). For example, whilst many previous workers have used diagnostic characteristics such as the shape, size and length of the median lobe (the key diagnostic character of the genus), as well as body colour, to distinguish Tor species, these characteristics are known to be highly variable within species (Roberts 1999;Menon 1992).…”

“…For example, whilst many previous workers have used diagnostic characteristics such as the shape, size and length of the median lobe (the key diagnostic character of the genus), as well as body colour, to distinguish Tor species, these characteristics are known to be highly variable within species (Roberts 1999;Menon 1992). This variability has been attributed to environmental influences, habitat changes (Hora 1939;Esa et al 2006) and trophic polymorphism (Walton et al 2017). Despite this, there have been very few studies that have explored how this plasticity contributes to the observed diversity of morphologies in mahseers.…”

“…1), this has been heavily skewed towards aquaculture (Kumar et al 2013;Norfatimah et al 2014;Raman et al 2016). While some of these studies provide strong contributions to the Tor taxonomic knowledge base (Hora 1939;Roberts 1999;Walton et al 2017), many fail to reference original species descriptions, type localities and lack the integration of morphological data that would assist field biologists (Nguyen et al 2008;Mani et al 2009). Furthermore, with frequent evidence of the 'blind' propagation of repetition and errors in citation networks (see Greenberg 2009), many studies (for e.g.…”