Competitive exclusion after invasion?

Abstract

The 'Competitive Exclusion Principle' is a foundation stone in the understanding of interspecific competition and niche relationships between species. In spite of having the status of a biological law, the principle has limited empirical support. In this study, we document strong effects of competition from the invading fish species vendace Coregonus albula over a 14-year period in the sub-arctic Pasvik watercourse. The native d.r. whitefish, that shared food and habitat niche with the invader, was displaced from its original niche and showed a more than 90% decline in population density over the study period. The study thus provides a unique record of how an exotic fish species excludes a native species from its original niche. Our data support the competitive exclusion principle, but also indicate that the vulnerability of the inferior competitor depends on a lack of alternative resources and on indirect ecological interactions.

Fauna crime: elucidating the potential source and introduction history of European smelt (Osmerus eperlanus L.) into Lake Storsjøen, Norway

“…predation and interspecific resource competition (Evans and Loftus 1987;Mercado-Silva et al 2007). Similar rapid effects has been observed for other systems and species, such as the intentionally introduction of Coregonus albula in the Pasvik watercourse (Northern Norway) (Mutenia and Salonen 1992;Bøhn et al 2008;Praebel et al 2013). Long-term population genetic and demographic monitoring of the smelt and the ecosystem in Lake Storsjøen is thus crucial since the introduction of smelt is likely to have implications for the food web.…”

Invader population speeds up life history during colonization

“…Vendace was observed in Lake Vaggatem for the first time in 1991 and had by 1995 established populations along the whole Pasvik system (Amundsen et al 1999). In Lake Vaggatem, the species also rapidly became the dominant species in gill net catches from the pelagic zone (Amundsen et al 1999), relegating whitefish from this habitat and the associated zooplankton food resources (Bøhn and Amundsen 2001;Bøhn et al 2008). …”

“…Vendace was introduced in Lake Inari, Finland, around 1960 (Mutenia and Salonen 1992), established a dense population and colonised downstream lakes in the Pasvik watercourse, Norway and Russia, where the species was observed for the first time in 1989 (Amundsen et al 1999). In Lake Vaggatem, Norway, in the upstream part of the Pasvik watercourse, the invader rapidly became the dominant pelagic fish species (Bøhn et al 2004(Bøhn et al , 2008. Long-term investigations with annual sampling of vendace have been carried out in Lake Inari since 1985 (Salonen 1998(Salonen , 2004 and in Lake Vaggatem since 1991 (Amundsen et al 1999;Bøhn et al 2008).…”

“…In Lake Vaggatem, Norway, in the upstream part of the Pasvik watercourse, the invader rapidly became the dominant pelagic fish species (Bøhn et al 2004(Bøhn et al , 2008. Long-term investigations with annual sampling of vendace have been carried out in Lake Inari since 1985 (Salonen 1998(Salonen , 2004 and in Lake Vaggatem since 1991 (Amundsen et al 1999;Bøhn et al 2008). Here we perform a combined analysis of these time-series in order to compare the population biology and life-history strategies of the source (Lake Inari) and colonist (Lake Vaggatem) populations of the invader species prior to and following the downstream invasion and establishment.…”

Untitled

“…Conversely, these increases in competitive interactions might result in the species exploiting a wider resource base and thus resulting in larger trophic niches (Svanbäck and Bolnick, 2007). If the introduced species is a superior competitor then their exploitation of the resources potentially results in the competitive exclusion of native species (Bøhn, Amundsen & Sparrow, 2008;Tran et al, 2015).…”