LOCAL ADAPTATION OF CHAOBORUS PUNCTIPENNIS TO SEASONAL AND CONSTANT PREDATION REGIMES

Species adapt to seasonality in their environment through a complex arrangement of life history events around the yearly cycle. Populations in the same climatic conditions are usually assumed to be adapted to similar seasonality. However, the behavior of other species can modify or create different seasonality in the biotic environment. We studied the adaptation of an invertebrate mesopredator, Chaoborus punctipennis, to the seasonal or constant presence of migratory and landlocked alewife, a zooplanktivorous fish. Alewife prey directly on Chaoborus larvae and strongly structure the zooplankton community when present, affecting prey availability for Chaoborus. We intensively sampled the abundance and size distribution of two populations of Chaoborus occupying one lake with landlocked alewife (constant predation and prey availability) and one with migratory alewife (highly seasonal predation and prey availability) weekly from June–October 2021, and monthly in three other lakes. We found that populations differed in their life history and morphology: Chaoborus in the lakes with migratory alewife exhibited one major reproductive event each summer, and grew to a larger terminal fourth instar size, while Chaoborus in the lakes with landlocked alewife reproduced twice a summer and reached a smaller fourth instar size. This shows that biotic seasonality can strongly and differentially structure lakes experiencing nearly identical environmental seasonality, and that this specific community context can lead to drastic differences in the characteristics of local populations.

Primary Presenter: Petra Wakker, Yale University (pabwakker@gmail.com)

Authors:

Petra Wakker, Yale University  (petra.wakker@yale.edu)

David Post, Yale University  (david.post@yale.edu)