Phenotypic response to different predator strategies can be mediated by temperature

Abstract

Temperature change affects biological systems in multifaceted ways, including the alteration of species interaction strengths, with implications for the stability of populations and communities. Temperature‐dependent changes to antipredatory responses are an emerging mechanism of destabilization and thus there is a need to understand how prey species respond to predation pressures in the face of changing temperatures. Here, using ciliate protozoans, we assess whether temperature can alter the strength of phenotypic antipredator responses in a prey species and whether this relationship depends on the predator's hunting behavior. We exposed populations of the ciliate Paramecium caudatum to either (i) a sit‐and‐wait generalist predator (Homalozoon vermiculare) or (ii) a specialized active swimmer predator (Didinium nasutum) across two different temperature regimes (15 and 25°C) to quantify the temperature dependence of antipredator responses over a 24‐h period. We utilized a novel high‐throughput automated robotic monitoring system to track changes in the behavior (swimming speed) and morphology (cell size) of P. caudatum at frequencies and resolutions previously unachievable by manual sampling. The change in swimming speed through the 24 h differed between the two temperatures but was not altered by the presence of the predators. In contrast, P. caudatum showed a substantial temperature‐dependent morphological response to the presence of D. nasutum (but not H. vermiculare), changing cell shape toward a more elongated morph at 15°C (but not at 25°C). Our findings suggest that temperature can have strong effects on prey morphological responses to predator presence, but that this response is potentially dependent on the predator's feeding strategy. This suggests that greater consideration of synergistic antipredator behavioral and physiological responses is required in species and communities subject to environmental changes.

Multivariate signals of population collapse in a high-throughput ecological experiment.

“…In contrast to the pollution treatment, the predator introduction, a press disturbance scenario, did not result in the predicted sequence of observable signals prior to a populations collapse. Whilst ciliates, and the Paramecium genus in particular, are known to display antipredatory behavioural and morphological responses (Cerini et al 2023b;Fyda et al 2005), neither behavioural nor morphological traits showed a clear pattern of change compared to the control in the predator treatment. Exposure to predatory Stenostomum cues induced a swimming speed reduction in Paramecium , and a cell shape change towards a ball-shape morph (to decrease likelihood of being engulfed by the predator, Hammillet al 2010b).…”