Temporally auto-correlated predator attacks structure ecological communities

For species regulated by a common predator, the P* rule predicts that the prey species that supports the highest mean predator density (P*) excludes the other prey species. This prediction is re-examined in the presence of temporal fluctuations in the vital rates of the interacting species including predator attack rates. When the fluctuations in predator attack rates are temporally uncorrelated, the P* rule still holds even when the other vital rates are temporally auto-correlated. However, when temporal auto-correlations in attack rates are positive but not too strongly, the prey species can coexist due to the emergence of a positive covariance between predator density and prey vulnerability. This coexistence mechanism is similar to the storage effect for species regulated by a common resource. Strongly positive or negative auto-correlations in attack rates generate a negative covariance between predator density and prey vulnerability and a stochastic priority effect can emerge: with non-zero probability either prey species is excluded. These results highlight how temporally auto-correlated species' interaction rates impact the structure and dynamics of ecological communities.

Climate Effects on Prey Vulnerability Modify Expectations of Predator Responses to Short- and Long-Term Climate Fluctuations

Climate changes affect the distribution and abundance of organisms, often via changes in species interactions. Most animals experience predation, and a number of models have investigated how climate fluctuations can influence predator–prey dynamics by affecting prey abundance through changes in resource availability. However, field studies have shown that prey vulnerability is a key feature determining the outcome of predator–prey interactions, which also varies with climatic conditions, via changes in prey body condition or in habitat characteristics (e.g. vegetation cover). In this theoretical work, we explore, with large mammals of African savannas in mind, how the interplay between climate-induced changes in prey abundance and climate-induced changes in prey vulnerability affects the immediate and long-term responses of predator populations. We account for prey body condition and habitat effects on prey vulnerability to predation. We show that predictions on how predator abundance responds to climate fluctuations differ depending on how climate influences prey vulnerability (habitat characteristics vs. prey body condition). We discuss how species traits influence the relative importance of the different sources of vulnerability. For example, our results suggest that populations of cursorial predators (such as spotted hyaenas) are expected to fare better than populations of ambush predators (such as African lions) in African ecosystems that will be characterised by an aridification. This study highlights the importance of understanding, and accounting for, the vulnerability factors associated to a given predator–prey pair, and improves our comprehension of predator–prey relationships in a changing climate.

Genetic variation in birds in relation to predation risk by hawks: A comparative analysis

The level of genetic variation among individuals may affect performance by reducing the ability of prey to detect and escape from predators if lack of genetic variation reduces flight ability directly or indirectly through reduced parasite resistance. We investigated vulnerability of common avian prey species to predation by the sparrowhawk Accipiter nisus and the goshawk A. gentilis in relation to an index of genetic similarity among adults of potential prey species. We estimated a prey vulnerability index that reflects the abundance of prey relative to the expected abundance according to local population density, and related this index to band sharing coefficients based on analyses of minisatellites for adults in local breeding populations. The prey vulnerability index was positively correlated with the band sharing coefficient in both predators, even when controlling for potentially confounding variables. These findings indicate that prey species with high band sharing coefficients, and hence low levels of genetic variation, are more readily caught by avian predators. Therefore, predation may constitute a major cost of low levels of genetic variation in extant populations of prey.