Elevational and climatic gradients shape the genetic structure of a typical Tibetan loach Triplophysa stenura (Cypriniformes: Nemacheilidae)

Abstract

Species resilience to diversified environments largely depends on their genetic diversity. Disentangling the respective roles of multiple landscape factors on population genetic variation could help us interpret the adaptive mechanism of species to environments, which is a central issue in evolutionary biology and biodiversity conservation. Herein, a typical Tibetan loach Triplophysa stenura was selected as study object to perform landscape genetics analyses inferred from mitochondrial cytochrome b gene sequences. Based on extensive sample collection, a total of 377 individuals from 20 sites in the Yarlung Tsangpo River were included in the analyses and results of genetic diversity assessment demonstrated relatively high haplotype diversity and low nucleotide diversity for most geographic populations. Genetic diversity pattern analysis proved that both haplotype and nucleotide diversity were greater in higher, colder and drier areas, which was consistent with the central-marginal hypothesis for this plateau hinterland-originated species. Degree of genetic differentiation among geographic populations varied from low level to extremely high level, with genetic variation coming mainly from within populations. Elevational and climatic divergences were detected to be principally responsible for the formation of population genetic structure of this species, coinciding with the isolation-by-environment model. On this basis, we put forward some applicable proposals that the marginal populations with relatively low elevations deserved more attentions in designing conservation scheme and those genetically differentiated populations should be treated as separate conservation units. In the context of global climate change and intensifying human activity, a sound genetic resources monitoring along elevational or climatic gradient is pivotal to develop future conservation interventions.