Differential invasion success of salmonids in southern Chile: patterns and hypotheses

Abstract

Biological invasions create complex eco- logical and societal issues worldwide. Most of the knowledge about invasions comes only from success- ful invaders, but less is known about which processes determine the differential success of invasions. In this review, we develop a framework to identify the main dimensions driving the success and failure of invaders, including human influences, characteristics of the invader, and biotic interactions. We apply this frame- work by contrasting hypotheses and available evi- dence to explain variability in invasion success for 12 salmonids introduced to Chile. The success of On- corhynchus mykiss and Salmo trutta seems to be influenced by a context-specific combination of their phenotypic plasticity, low ecosystem resistance, and propagule pressure. These well-established invaders may limit the success of subsequently introduced salmonids, with the possible exception of O. tshawyts- cha, which has a short freshwater residency and limited spatial overlap with trout. Although propagule pressure is high for O. kisutch and S. salar due to their intensive use in aquaculture, their lack of success in Chile may be explained by environmental resistance, including earlier spawning times than in their native ranges, and interactions with previously established and resident Rainbow Trout. Other salmonids have also failed to establish, and they exhibit a suite of ecological traits, environmental resistance, and lim- ited propagule pressure that are variably associated with their lack of success. Collectively, understanding