How patch size and habitat complexity changes interaction strength and population dynamics: a combined individual-based and population-based modeling experiment

Y Li, U Brose, K Meyer, and BC Rall
PeerJ Preprints 5:e2993, , 2017.

Understanding how functional responses (non-linear prey density dependent feeding interactions) are affected by patch size and habitat complexity is crucial as functional responses are the major determinants of food web stability and subsequently biodiversity. Due to its laborious character, measuring empirical functional responses systematically across large gradients of patch sizes and habitat complexity independently is almost impossible. Here we overcame this issue by using an individual-based predator-prey model allowing to simulate functional responses in patches ranging from the size of petri dishes to natural patches in the field. Moreover we are able to vary the habitat complexity independent of the patch size. Contradicting to the pervasive type II functional response that is still assumed as the appropriate model to describe feeding interactions we found a type III functional response in our simulations, independent of patch size and habitat complexity. Moreover, half-saturation density determining the feeding success at low prey densities decrease only with increasing habitat complexity and is only marginally influenced by patch size. Subsequent population dynamic model simulations indicate that small patches do not allow for survival of the predator, caused by a mismatch of the nearly constant functional response but an increasing extinction boundary with decreasing patch size. This effect is counteracted by increasing habitat complexity allowing both, the prey and the predator to co-exist. Our results underline the need for protecting large patches with high habitat complexity to sustain biodiversity.

(fulltext link)
doi: 10.7287/peerj.preprints.2190v1
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