Abstract

Native predators can influence prey competition by consumption, risk of mortality, or both (Connell 1975, Gurevitch et al. 2000). In particular, prey preference of a predator can influence overall effects of predation on competition depending on which competitor is the preferred prey and if the predator switches between prey species (Murdoch 1969, Roughgarden & Feldman 1975). Invasive predators often cause declines in native species (Mack et al. 2000) that are typically more severe than native predators (Salo et al. 2007), so it is likely invasive predators are capable of influencing competitive interactions among native species based on the invasive predator’s prey preferences. This could enhance or moderate the effects of native predation based on whether the native and invasive predators share a similar prey preference or have differing preferences. To gain insight as to whether an invasive predator can alter competition between native prey, we performed a series of controlled experiments in aquaria to characterize and compare the prey preferences of the invasive red lionfish (Pterois volitans) and an ecologically-similar native mesopredator, the graysby grouper (Cephalopholis cruentata) between competing native fairy and blackcap basslets (Gramma loreto and G. melacara, respectively). We predicted that as generalist mesopredators, lionfish and graysby would have similar prey preferences. We predicted that neither predator would display a preference between basslet species but as gape-limited predators, would exhibit shifts in preference from small to large basslets with increasing predator size.

PDF Preview