Thermal acclimation of interactions: differential responses to temperature change alter predator-prey relationship

Abstract

Different species respond differently to environmental change so that species interactions cannot be predicted from single-species performance curves. We tested the hypothesis that interspecific difference in the capacity for thermal acclimation modulates predator-prey interactions. Acclimation of locomotor performance in a predator (Australian bass, Macquaria novemaculeata) was qualitatively different to that of its prey (eastern mosquitofish, Gambusia holbrooki). Warm (25°C) acclimated bass made more attacks than cold (15°C) acclimated fish regardless of acute test temperatures (10-30°C), and greater frequency of attacks was associated with increased prey capture success. However, the number of attacks declined at the highest test temperature (30°C). Interestingly, escape speeds of mosquitofish during predation trials were greater than burst speeds measured in a swimming arena, whereas attack speeds of bass were lower than burst speeds. As a result, escape speeds of mosquitofish were greater at warm temperatures (25°C and 30°C) than attack speeds of bass. The decline in the number of attacks and the increase in escape speed of prey means that predation pressure decreases at high temperatures. We show that differential thermal responses affect species interactions even at temperatures that are within thermal tolerance ranges. This thermal sensitivity of predator-prey interactions can be a mechanism by which global warming affects ecological communities.

Figure 1.

(a,c,e,g) Swimming performance in bass and (b,d,f,h) mosquitofish. There were interactions between acclimation treatment and test temperatures for sustained swimming performance (U_crit) in (a) bass and (b) mosquitofish, as well as for burst swimming in (c) bass and (d) mosquitofish. Similarly, there was an interaction between acclimation treatment and test temperature in attack speeds of (e) bass, but escape speeds of (f) mosquitofish did not change significantly with acclimation treatment or test temperature. Interestingly, attack speeds of bass were significantly lower than burst speeds measured in the swimming arena, but escape speeds of mosquitofish were significantly higher than burst speeds. Absolute escape speeds of (h) mosquitofish were significantly higher than attack speeds of (g) bass at 25°C and 30°C. Black bars represent cold-acclimated fish and white bars represent warm-acclimated fish. Means and s.e. are shown, and results of statistical analyses are indicated in each panel.

Figure 2.

Predator–prey interactions. (a) Warm-acclimated bass were quicker to attack than cold-acclimated fish, and (b) attacked for longer. (c) Warm-acclimated bass also made more attacks than cold-acclimated fish, particularly at warm temperatures, although the number of attacks decreased at the highest temperature. (d) The success of bass in capturing prey (the proportion of the ten independent predation trials in which bass captured a mosquitofish) increased linearly with the number of attacks made per minute; the regression line ±95% confidence intervals are shown. Black bars and circles represent cold-acclimated fish, and white bars and circles represent warm-acclimated fish. (a–c) Means and s.e. are shown, and results of statistical analyses are indicated in each panel.