The invasive predator Bythotrephes induces changes in the vertical distribution of native copepods in Lake Michigan

Abstract

Invasive predators can have large negative effects on native prey populations. The susceptibility of native prey to invasive predators may depend on their ability to respond behaviorally to the presence of these non-native predators. In a field survey conducted in Lake Michigan over several years, we found that high densities of the invasive predatory cladoceran Bythotrephes were correlated with lower vertical distributions of some species and age classes of native copepods; moving from inhabiting primarily the epiliminion at low Bythotrephes density to primarily the hypolimnion at high Bythotrephes density. Five groups showed this pattern; diaptomid copepodites, adult cyclopoids, Diacyclops thomasi, and the adult diaptomids Leptodiaptomus ashlandi and L. minutus. In contrast, Bythotrephes density was not correlated with the vertical distribution of copepod nauplii and adult L. sicilis. Laboratory experiments suggest that the changes in the vertical distribution in the field at high Bythothrephes are due to an inducible, plastic response to predation threat from Bythotrephes signaled by water-borne cues. Species that were lower in the field at high Bythotrephes densities responded behaviorally to water-borne cues from Bythotrephes by moving to lower levels of experimental water columns. These species included D. thomasi and L. minutus, with L. ashlandi displaying a non-significant trend in the same direction. In contrast, L. sicilis, which was not correlated with Bythotrephes density in the field, was unaffected by the water-borne cues. Differences in vertical distribution shifts among these native copepod species and life-history stages are likely due to speciesspecific differences in spatial overlap with Bythotrephes and their relative ability to migrate large distances or employ alternative avoidance strategies. The varied responses exhibited among the copepod groups likely alter their interactions with each other, their resources and other predators, thus revealing the complex effects Bythotrephes can have on invaded communities.

Finely tuned response of native prey to an invasive predator in a freshwater system

“…Support for this view is found in several studies reporting a lack of recognition of invasive predators by native prey that lack an evolutionary history with the predator (Shave et al 1994, Kiesecker and Blaustein 1997). However, both invertebrate and vertebrate prey have been shown to respond effectively to invasive predators in freshwater (Nannini and Belk 2006, Stuart-Smith et al 2008, Bourdeau et al 2011, marine (Freeman and Byers 2006), and terrestrial (Carthey and Banks 2012) systems. For example, native prey fish in relatively isolated rivers and marshes have been shown to respond appropriately to nonnative predatory fish, despite no previous history with them (Rehage et al 2009, Kovalenko et al 2010, DunlopHayden and Rehage 2011.…”

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

“…Here, we fill several fundamental holes in understanding about Bythotrephes. In terms of population and community dynamics, Brown and Branstrator (2011) and Wittmann et al (2011) demonstrate the role of the resting egg biology of Bythotrephes on its invasion success, while Pichlová-Ptácníková and Vanderploeg (2011), Bourdeau et al (2011), andYoung et al (2011), respectively, consider how differences in prey avoidance abilities, migration tendencies, and spring abundances can explain the invader's abundance, and its differential impacts on specific taxa. Hessen et al (2011) and Jokela et al (2011) compare the invader's interactions with native macro-invertebrate, holoplanktonic predators in Norway and Canada; Kerfoot et al (2011) prove the role of fish in its dispersal; while Rennie et al (2011) document the overall changes in trophic structuring of food webs that follow invasion.…”

“…In lakes of all sizes, the diversity of crustacean zooplankton, particularly its cladoceran component, has fallen (Lehman and Caceres 1993;Schulz and Yurista 1999;Yan and Pawson 1997;Yan et al 2001Yan et al , 2002Barbiero and Tuchman 2004;Strecker et al 2006), both because Bythotrephes consumes a very large fraction of total zooplankton production (Dumitru et al 2001;Strecker and Arnott 2008), and indirectly because Bythotrephes induces downward migration of its prey into deeper cooler waters that lower their growth rates (Pangle et al 2007;Bourdeau et al 2011). 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 .…”

“…In this collection we learn more about such indirect effects. Jokela et al (2011) demonstrate alterations in the vertical distributions of the invader's macro-invertebrate competitors, while Bourdeau et al (2011) used chemical cues from the invader to induce alterations in the diel vertical distribution of copepods in Lake Michigan waters. 8.…”

Dynamics of the invasive spiny water flea, Bythotrephes longimanus, in Lake Simcoe, Ontario, Canada

“…Bythotrephes is a voracious predator of crustacean zooplankton, capable of altering the trophic structure of lakes (Rennie et al 2011). Its invasion is routinely associated with reductions in the species richness of crustacean zooplankton and cladoceran standing stocks (Yan and Pawson 1997, Dumitru et al 2001, Boudreau and Yan 2003, Barbiero and Tuchman 2004, Strecker et al 2006, alterations in the behaviour of the zooplankton (Pangle et al 2007, Young and Yan 2008, Bourdeau et al 2011, and the displacement of native predatory invertebrates Sprules 2009, Weisz and. Bythotrephes may compete with planktivorous fish for prey (Lehman 1991, Garton et al 1993, Hoffman et al 2001, Foster and Sprules 2010, diverting energy away from higher trophic levels (Dumitru et al 2001, Strecker and Arnott 2008, Foster and Sprules 2010.…”