Physiological Trade-Offs Along a Fast-Slow Lifestyle Continuum in Fishes: What Do They Tell Us about Resistance and Resilience to Hypoxia?

Rick J Stoffels,Jodie L Rummer

doi:10.1371/journal.pone.0130303

Abstract

It has recently been suggested that general rules of change in ecological communities might be found through the development of functional relationships between species traits and performance. The physiological, behavioural and life-history traits of fishes are often organised along a fast-slow lifestyle continuum (FSLC). With respect to resistance (capacity for population to resist change) and resilience (capacity for population to recover from change) to environmental hypoxia, the literature suggests that traits enhancing resilience may come at the expense of traits promoting resistance to hypoxia; a trade-off may exist. Here I test whether three fishes occupying different positions along the FSLC trade-off resistance and resilience to environmental hypoxia. Static respirometry experiments were used to determine resistance, as measured by critical oxygen tension (Pcrit), and capacity for (RC) and magnitude of metabolic reduction (RM). Swimming respirometry experiments were used to determine aspects of resilience: critical (U crit) and optimal swimming speed (U opt), and optimal cost of transport (COTopt). Results pertaining to metabolic reduction suggest a resistance gradient across species described by the inequality Melanotaenia fluviatilis (fast lifestyle) < Hypseleotris sp. (intermediate lifestyle) < Mogurnda adspersa (slow lifestyle). The Ucrit and COTopt data suggest a resilience gradient described by the reverse inequality, and so the experiments generally indicate that three fishes occupying different positions on the FSLC trade-off resistance and resilience to hypoxia. However, the scope of inferences that can be drawn from an individual study is narrow, and so steps towards general, trait-based rules of fish community change along environmental gradients are discussed.

Highlights

Species’ physiological tolerances play an important role in driving spatiotemporal change in abundance, community composition [1, 2]
In contrast with the Pcrit results, the metabolic reduction results generally supported the hypothesis of a hypoxia resistance gradient described by M. fluviatilis < Hypseleotris < M. adspersa (Fig 2C and 2D)
The functional-traits approach to community ecology is currently at the forefront of ecological thinking, and studies that experimentally demonstrate links between organismal traits and performance trade-offs along environmental gradients contribute to the quest for general rules of community change [4]

Summary

Introduction

Species’ physiological tolerances play an important role in driving spatiotemporal change in abundance, community composition [1, 2]. Physiology and Fish Community Change physiology of multiple species, towards understanding the mechanistic basis of community change, have been criticised by ecologists for being too ‘reductionist’ in their approach (discussed in [3]). The validity of this criticism has recently been questioned [4, 5]. McGill et al [4] have argued that greater predictive understanding might be achieved in community ecology through understanding how the physiological performances of key species traits respond to abiotic environmental gradients (the ‘functional-traits approach’). A challenge, is to identify the traits that capture the most information about physiological response to abiotic gradients

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Conclusion