Two‐step dialogue between the cladoceran Bosmina and invertebrate predators: Induction and natural selection

Abstract

Aquatic prey species respond to predators with fast (developmental) and slow (selective) feedbacks. Natural selection is assumed to fashion details of induction and to modify baseline morphology, but only rarely do we catch the slower (multi-generation) process in action. Laboratory experiments with Bosmina detected predatormediated induction and estimated spine heritability (h 2 5 0.2-0.5). Third Sister Lake, Michigan, U.S.A., Bosmina exhibited induction to resident (Mesocyclops) and to two nonresident, neighborhood predators (Epischura and Leptodora). However, the magnitude of induction in Third Sister Lake Bosmina to nonresident predators (Epischura, Leptodora) was muted, when compared with induction and final spine lengths in Epischura-Leptodora lakes. Inadvertent escape of Leptodora into Third Sister Lake in 1987 created a long-term (multiyear), whole-lake experiment, where resident Bosmina populations fell under intense size selection. During the interval, Leptodora suppressed a late-season smaller, short-featured species (B. freyii), favored seasonal expansion of an overwintering long-featured species (B. liederi), and selected for longer features in the latter species. Before local extinction, defensive spines of B. liederi achieved lengths comparable to populations that co-occur with Epischura and Leptodora.

A plague of waterfleas (Bythotrephes): impacts on microcrustacean community structure, seasonal biomass, and secondary production in a large inland-lake complex

“…Why does the spiny cladoceran, an invasive species, have such a widespread effect on North American resident assemblages, but not a comparable effect on European assemblages of similar composition? We would argue that natural selection and evolution of defensive mechanisms in prey species over time is a key response circumvented by Bythotrephes (for natural responses to Epischura and Leptodora, see Kerfoot and McNaught 2010). An upcoming article (Kerfoot and Savage 2016) discusses 55 split-clone experiments with three small prey species and 12 different predators from three locations in North America and three in Europe.…”

“…Although modern electrophoretic and genesequencing studies show that the predominantly European species B. longirostris does exist in North America, two recently described small-bodied species, B. liederi and B. freyii, are the usual upper Midwestern species in larger lakes (Taylor et al 2002;Kerfoot and McNaught 2010). The genus Eubosmina can be distinguished from the two smaller Bosmina species by lateral head pore position.…”

“…Prior studies established that small cladocerans, like Bosmina, undergo spine elongation and increased body size when placed in close proximity to many natural invertebrate predators (Kerfoot 1987;Kerfoot and McNaught 2010 Kerfoot and McNaught 2010). Bosmina stem females were netted (125 lm Nitex plankton net, towed vertically) from Portage Lake, Michigan, which is connected to Lake Superior.…”

“…Previous studies have established that the distribution of spine lengths closely resemble the normal distribution, although a positive relationship between the standard deviation and mean reveals an underlying log normal distribution (Kerfoot 1988). Moreover, spine length often remains nearly constant over body size, simplifying statistical comparisons (Kerfoot 1987;Kerfoot and McNaught 2010;Kerfoot and Savage 2016). Here mean spine elongation (predator treatment spine length-control length) from multiple ''split-culture'' experiments were compared using t tests.…”

Multiple inducers in aquatic foodwebs: Counter-measures and vulnerability to exotics

“…Individuals in control jars were much more morphologically uniform, whereas those in predation vessels were more highly variable. High variability in the presence of predators was noticed earlier in Third Sister Lake, Michigan, bag experiments (Kerfoot and McNaught ), and suggests that cues (chemical and/or mechanical signals) are related to physical proximity of predators and promote variable responses.…”