Intrageneric differences in the effects of acute temperature exposure on competitive behaviour of damselfishes.

Donald T Warren,Mark I Mccormick

doi:10.7717/peerj.7320

Abstract

Projected increases in global temperatures brought on by climate change threaten to disrupt many biological and ecological processes. Tropical ectotherms, like many fishes, can be particularly susceptible to temperature change as they occupy environments with narrow thermal fluctuations. While climate change models predict temperatures to increase over decades, thermal fluctuations are already experienced on a seasonal scale, which may affect the ability to capture and defend resources across a thermal gradient. For coral reef fish, losers of competitive interactions are often more vulnerable to predation, and this pressure is strongest just after settlement. Competitive interactions may determine future success for coral reef fishes, and understanding how temperature experienced during settlement can influence such interactions will give insight to community dynamics in a future warmer world. We tested the effect of increased temperatures on intraspecific competitive interactions of two sympatric species of reef damselfish, the blue damselfish Pomacentrus nagasakiensis, and the whitetail damselfish Pomacentrus chrysurus. Juvenile fishes were exposed to one of four temperature treatments, ranging from 26–32 °C, for seven days then placed into competitive arenas where aggressive interactions were recorded between sized matched individuals within each species. While there was no apparent effect of temperature treatment on aggressive behaviour for P. chrysurus, we observed up to a four-fold increase in aggression scores for P. nagasakiensis with increasing temperature. Results suggest that temperature experienced as juveniles can impact aggressive behaviour; however, species-specific thermal tolerances led to behavioural affects that differ among closely related species. Differential thermal tolerance among species may cause restructuring of the interaction network that underlies the structure of reef assemblages.

Highlights

Temperature is an important abiotic factor that can have profound effects on behaviour, physiology, and life-history traits (Schulte, Healy & Fangue, 2011)
The one-way ANOVA for P. nagasakiensis, revealed aggression scores were lowest at ambient (28 ◦C) and increased as temperature moved from ambient in either direction (F3,73 = 14.78, p < 0.001; Fig. 3)
When aggression score differences were separated by competitor, dominant P. nagasakiensis scores tended to increase with temperature while subordinate scores decreased

Summary

Introduction

Temperature is an important abiotic factor that can have profound effects on behaviour, physiology, and life-history traits (Schulte, Healy & Fangue, 2011). Climate change models predict sea surface temperature will rise as much as +3 ◦C by 2100 (Collins et al, 2013), impacting the ecology of many species (Walther et al, 2002). Even within tropical ecosystems, which are considered relatively thermally stable, coral reefs can experience seasonal thermal variation of 8 ◦C (McCabe et al, 2010). This effect of temperature change can be more pronounced in ectotherms as their metabolism tends to increase nearly exponentially with rising temperature (Clarke & Johnston, 1999). Studying how reef species respond to temperature change can be helpful for determining the impact future climate change will have

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Discussion

Conclusion