Abstract
There is growing evidence of rapid genetic adaptation of natural populations to environmental change, opening the perspective that evolutionary trait change may subsequently impact ecological processes such as population dynamics, community composition, and ecosystem functioning. To study such eco‐evolutionary feedbacks in natural populations, however, requires samples across time. Here, we capitalize on a resurrection ecology study that documented rapid and adaptive evolution in a natural population of the water flea Daphnia magna in response to strong changes in predation pressure by fish, and carry out a follow‐up mesocosm experiment to test whether the observed genetic changes influence population dynamics and top‐down control of phytoplankton. We inoculated populations of the water flea D. magna derived from three time periods of the same natural population known to have genetically adapted to changes in predation pressure in replicate mesocosms and monitored both Daphnia population densities and phytoplankton biomass in the presence and absence of fish. Our results revealed differences in population dynamics and top‐down control of algae between mesocosms harboring populations from the time period before, during, and after a peak in fish predation pressure caused by human fish stocking. The differences, however, deviated from our a priori expectations. An S‐map approach on time series revealed that the interactions between adults and juveniles strongly impacted the dynamics of populations and their top‐down control on algae in the mesocosms, and that the strength of these interactions was modulated by rapid evolution as it occurred in nature. Our study provides an example of an evolutionary response that fundamentally alters the processes structuring population dynamics and impacts ecosystem features.
Highlights
Ecological and evolutionary dynamics have long been considered as largely uncoupled and independent processes
While top-down control in the Control treatment decreased from the pre-fish to the reduced-fish population, we found no significant differences between populations in the extent of phytoplankton blooms in the presence of fish predation
Our results indicate that evolution in this natural Daphnia populations did result in a differential top-down control of phytoplankton and in subtle differences in the dynamics of the Daphnia populations themselves
Summary
Ecological and evolutionary dynamics have long been considered as largely uncoupled and independent processes. We here took the opportunity to test the hypothesis of a feedback of evolution as it occurred in nature on a key ecosystem function in an outdoor mesocosm experiment in which we quantified Daphnia population densities and phytoplankton biomass over time in mesocosms inoculated with a representative set of clones of the three resurrected populations studied by Cousyn et al (2001) and Stoks et al (2016) These populations strongly differ in life-history and behavioral traits (Stoks et al, 2016) and were here inoculated in mesocosms that did or did not contain fish. We engaged in an effort to elucidate the mechanisms underlying the observed differences between the populations that were resurrected from a layered egg bank of a single pond and document evolution as it occurred in a single population over a period of approximately 16 years
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