Shifting invertebrate zooplanktivores: watershed-level replacement of the native Leptodora by the non-indigenous Bythotrephes in Canadian Shield lakes

Abstract

The abundance of the native, pelagic macroinvertebrate predator, Leptodora kindtii, is negatively correlated with the abundance of a new invasive competitor, Bythotrephes longimanus, in a small number of Canadian Shield lakes. However, we do not yet know if Bythotrephes is replacing Leptodora on a regional scale. We determined the distribution of both species in 166 lakes in the District of Muskoka, south-central Ontario, Canada-the watershed with the longest history and largest prevalence of Bythotrephes invasions in North America. The frequency of occurrence of Leptodora was substantially reduced (twofold) in the presence of Bythotrephes. We argue that Bythotrephes is responsible for this dramatic reduction in the frequency of occurrence of Leptodora. Lakes in which both species co-occurred could not be distinguished from invaded lakes without Leptodora, suggesting a pattern of species replacement at a watershed level. We believe this is the first account of the widespread replacement of a native, pelagic macroinvertebrate predator by Bythotrephes in North America, and it does not bode well for Leptodora given the rapid, ongoing spread of Bythotrephes.

The ecological niches of Bythotrephes and Leptodora: lessons for predicting long-term effects of invasion

“…Hence for various reasons, Leptodora seem to occupy primarily the lakes where Bythotrephes is excluded by heavy fish predation and/or high productivity and turbid waters, or high temperature (Enz et al 2001). As an invader, Bythotrephes is thus likely to exclude Leoptodora from lakes (Foster and Sprules 2010;Weisz and Yan 2010), hence shifting the predatory regimes. The fact that the species rarely co-occur in the surveyed lakes could simply reflect a long history of geographical coexistence and thus represent the ''ghost of competition past'' (cf.…”

The spread, establishment and impacts of the spiny water flea, Bythotrephes longimanus, in temperate North America: a synopsis of the special issue

“…While Bythotrephes is not considered problematic in Europe, the situation is quite different in North America, where it has proven to be a serious threat to pelagic biodiversity in both large and small lakes (Yan et al 2002;Barbiero and Tuchman 2004;Strecker et al 2006). Its damaging effects cascade below its immediate crustacean prey to pelagic rotifers (Hovius et al 2006), and likely to phytoplankton , and also up the food chain to competing macro-invertebrate predators (Foster and Sprules 2009;Weisz and Yan 2011) and fish (Parker-Stetter et al 2005).…”

“…The impacts of the invader also cascade beyond their immediate crustacean prey, down the food chain to rotifers, which apparently benefit from competitive release (Hovius et al 2006(Hovius et al , 2007, and likely to phytoplankton . Effects also are felt up the food chain to competing macro-invertebrate predators, at least one of which (Leptodora) suffers dramatic losses (Foster and Sprules 2009;Weisz and Yan 2011), and to fish, whose behaviour and diet changes (Mills et al 1992;Parker Stetter et al 2005).…”

“…We learn from an examination of Norwegian lakes that the ongoing replacement of Leptodora by Bythotrephes in North America (Foster and Sprules 2009;Weisz and Yan 2011) might well have been predicted from their co-occurrence patterns in Europe (Hessen et al 2011). Finally, we learn that spring prey abundance may well be the prime determinant of Bythotrephes population size , and perhaps, establishment success, given the large Allee effect.…”

Patterns of Bythotrephes longimanus distribution relative to native macroinvertebrates and zooplankton prey

“…An asterisk denotes significant differences (P \ 0.05) following sequential Bonferroni adjustment Patterns of Bythotrephes longimanus distribution 2581 other way around. Rapid declines in Leptodora abundance and negative correlations with Bythotrephes abundance have been observed in North American lakes following invasion (Garton et al 1990;Branstrator and Lehman 1991;Yan and Pawson 1997;Foster and Sprules 2009;Weisz and Yan 2011). This trend is likely indicative of the superior competitive ability of Bythotrephes under many conditions as well as some predation on Leptodora by Bythotrephes (Branstrator 1995(Branstrator , 2005.…”