Evolutionary history of Daphnia drives divergence in grazing selectivity and alters temporal community dynamics of producers

Abstract

Consumers with different seasonal life histories encounter different communities of producers during specific seasonal phases. If consumers evolve to prefer the producers that they encounter, then consumers may reciprocally influence the temporal composition of producer communities. Here, we study the keystone consumer Daphnia ambigua, whose seasonal life history has diverged due to intraspecific predator divergence across lakes of New England. We ask whether grazing preferences of Daphnia have diverged also and test whether any grazing differences influence temporal composition patterns of producers. We reared clonal populations of Daphnia from natural populations representing the two diverged life history types for multiple generations. We conducted short‐term (24 hr) and long‐term (27 days) grazing experiments in equal polycultures consisting of three diatom and two green algae species, treated with no consumer, Daphnia from lakes with anadromous alewife, or from lakes with landlocked alewife. After 24 hr, life history and grazing preference divergence in Daphnia ambigua drove significant differences in producer composition. However, those differences disappeared at the end of the 27‐day experiment. Our results illustrate that, despite potentially more complex long‐term dynamics, a multitrophic cascade of evolutionary divergence from a predator can influence temporal community dynamics at the producer level.

Effects of size selection versus density dependence on life histories: A first experimental probe

“…For example in a previous study (Pantel et al, 2015) Daphnia that were locally adapted to conditions with or without fish significantly altered zooplankton community assembly. In another study (Park et al 2018) Daphnia that diverged in life history in response to fish predation not only increased their resistance to being eaten but also had distinct grazing preferences. Hence, density‐dependent selection and size selection acting on a single species has the potential to change the composition of primary producers and reduce the abundance of their consumers.…”