Hydrogeomorphic factors drive differences in otolith morphology in fish from the Nu‐Salween River

Abstract

Understanding the relationship between intraspecific phenotypic variation and habitat is fundamentally important to ecology and evolution. However, it is largely unknown whether the environment drives the morphological variation in riverine fish otoliths, which are potential phenotypic markers. In this study, we investigated morphological variations in the otoliths of an endemic Chinese fish (Schizothorax nukiangensis Tsao) collected from seven sites with varying environmental gradients along the Nu‐Salween River. We compared morphological characters of S. nukiangensis otoliths among sampling sites and identified environmental sources of otolith morphological variation using multivariate regression trees and multiple factor analysis. Results showed that S. nukiangensis otoliths collected from different habitats were significantly different in morphology, mainly at the rostrum, excisura and posterior rim. Variations in otolith morphology (specifically the increase in otolith length) were predominantly governed by average river gradient; this might be a functional response to hydrogeomorphic conditions. Other environmental gradients (i.e., altitude, latitude and average annual temperature) played a minor role in otolith shape. This study highlighted the role of environmental factors in determining the otolith shape in riverine fish; thus, species and population discriminations based on otolith morphology should consider intraspecific variability.

Parallel late ontogeny transformations in contrasting landlocked phenotypes ofSalvelinus malma(Salmonidae) from small volcanic lakes

“…On the contrary, the complicated dynamics most naturally should force the phenotype specialisation towards lacustrine lifestyle in small-numbered isolated populations. The parallel origin of lacustrine morphotype was reported for charrs (Kristjansson, Leblanc, Skulason, Snorrason, & Noakes, 2018;Kristjansson et al, 2012) and other fish taxa (Ding et al, 2019;Franssen, Harris, Clark, Schaefer, & Stewart, 2013;Kaeuffer, Peichel, Bolnick, & Hendry, 2012); a similar morphotypes have evolved from independent populations after colonising similar environments. Herewith, we found the prevalence of unique morphological and anatomical features in six populations derived from common S. malma.…”

Morphological differentiation of the otoliths of graylings from the Barguzin River and Lake Baikal

“…Previously L. Ding and coauthors (Ding et al, 2019) found that the variability of the otoliths of Schizothorax nukiangensis Tsao, 1964 could be related to the river dynamics driven by its fall. They showed the otoliths of S. nukiangensis sampled in different habitats had a significantly different morphology, in particular they reported an increase of their length.…”

Low‐trophic level fishes and riverbank trees showed similar growth responses to climate warming on the Tibetan Plateau

“…S. nukiangensis is an endemic species in the Nujiang River. It inhabits cold and fast-flowing water and has the widest distribution area, with an elevation range from 700 to 3800 m (Ding et al, 2019). It grows slowly and can live up to 22 years with a maximum total length >75 cm (Ding et al, 2019).…”