Contrasting habitat associations of imperilled endemic stream fishes from a global biodiversity hot spot

Abstract

BackgroundKnowledge of the factors that drive species distributions provides a fundamental baseline for several areas of research including biogeography, phylogeography and biodiversity conservation. Data from 148 minimally disturbed sites across a large drainage system in the Cape Floristic Region of South Africa were used to test the hypothesis that stream fishes have similar responses to environmental determinants of species distribution. Two complementary statistical approaches, boosted regression trees and hierarchical partitioning, were used to model the responses of four fish species to 11 environmental predictors, and to quantify the independent explanatory power of each predictor.ResultsElevation, slope, stream size, depth and water temperature were identified by both approaches as the most important causal factors for the spatial distribution of the fishes. However, the species showed marked differences in their responses to these environmental variables. Elevation and slope were of primary importance for the laterally compressed Sandelia spp. which had an upstream boundary below 430 m above sea level. The fusiform shaped Pseudobarbus ‘Breede’ was strongly influenced by stream width and water temperature. The small anguilliform shaped Galaxias ‘nebula’ was more sensitive to stream size and depth, and also penetrated into reaches at higher elevation than Sandelia spp. and Pseudobarbus ‘Breede’.ConclusionsThe hypothesis that stream fishes have a common response to environmental descriptors is rejected. The contrasting habitat associations of stream fishes considered in this study could be a reflection of their morphological divergence which may allow them to exploit specific habitats that differ in their environmental stressors. Findings of this study encourage wider application of complementary methods in ecological studies, as they provide more confidence and deeper insights into the variables that should be managed to achieve desired conservation outcomes.

Evolutionary Drivers of Diversification and Distribution of a Southern Temperate Stream Fish Assemblage: Testing the Role of Historical Isolation and Spatial Range Expansion

“…‘Breede’. Chakona & Swartz [76] reported that Sandelia lineages in undisturbed tributaries of the Breede River system are restricted to river reaches below 425 m elevation, while Galaxias sp. ‘nebula’ and Pseudobarbus sp.…”

Swimming with the giant: coexistence patterns of a new redfin minnow Pseudobarbus skeltoni from a global biodiversity hot spot

“…Fine‐scale geographic sampling approaches and recent phylogeographic studies have facilitated more accurate mapping of the distribution ranges of stream fishes in the CFE (Chakona and Swartz ; Chakona et al. ).…”

“…Fine-scale geographic sampling approaches and recent phylogeographic studies have facilitated more accurate mapping of the distribution ranges of stream fishes in the CFE (Chakona and Swartz 2012;). This study focused on three co-occurring taxa in the Upper Riviersonderend River: the recently described P. skeltoni , the Breede lineage of P. burchelli (hereafter P. burchelli sp.…”

A freshwater fish defies ancient mountain ranges and drainage divides: extrinsic and intrinsic influences on the evolutionary history of a recently identified galaxiid

“…‘nebula’ to exploit dispersal corridors across drainage divides can be attributed to a number of factors. This lineage penetrates to higher elevations in mountain tributaries of the CFR than other native fishes (Chakona & Swartz, ). Opportunities for temporary inter‐basin connections are more likely at higher elevations than in lower parts of the basin.…”