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 (h2 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.