Habitat simplification increases the impact of a freshwater invasive fish
Environmental Biology of Fishes
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa; Department of Ichythology and Fisheries Science, Rhodes University, P.O. Box 94, Grahamstown, South Africa; South African Institute for Aquatic Biodiversity (SAIAB), Private Bag 1015, Grahamstown, South Africa; Centre for Invasion Biology, SAIAB, Private Bag 1015, Grahamstown, South Africa; Institute for Global Food Security, School of Biological Sciences, Queen’s University Belfast, MBC, 97 Lisburn Road, Belfast, Northern Ireland, United Kingdom
Biodiversity continues to decline at a range of spatial scales and there is an urgent requirement to understand how multiple drivers interact in causing such declines. Further, we require methodologies that can facilitate predictions of the effects of such drivers in the future. Habitat degradation and biological invasions are two of the most important threats to biodiversity and here we investigate their combined effects, both in terms of understanding and predicting impacts on native species. The predatory largemouth bass Micropterus salmoides is one of the World’s Worst Invaders, causing declines in native prey species, and its introduction often coincides with habitat simplification. We investigated the predatory functional response, as a measure of ecological impact, of juvenile largemouth bass in artificial vegetation over a range of habitat complexities (high, intermediate, low and zero). Prey, the female guppy Poecilia reticulata, were representative of native fish. As habitats became less complex, significantly more prey were consumed, since, even although attack rates declined, reduced handling times resulted in higher maximum feeding rates by bass. At all levels of habitat complexity, bass exhibited potentially population de-stabilising Type II functional responses, with no emergence of more stabilising Type III functional responses as often occurs in predator-prey relationships in complex habitats. Thus, habitat degradation and simplification potentially exacerbate the impact of this invasive species, but even highly complex habitats may ultimately not protect native species. The utilisation of functional responses under varying environmental contexts provides a method for the understanding and prediction of invasive species impacts. © 2014, Springer Science+Business Media Dordrecht.
DMR, Department of Science and Technology, Republic of South Africa; DST, Department of Science and Technology, Republic of South Africa; NRF, Department of Science and Technology, Republic of South Africa; 85,417, Department of Science and Technology, Re