Abstract
Species’ ecology and evolution can have strong effects on communities. Both may change concurrently when species colonize a new ecosystem. We know little, however, about the combined effects of ecological and evolutionary change on community structure. We simultaneously examined the effects of top-predator ecology and evolution on freshwater community parameters using recently evolved generalist and specialist ecotypes of three-spine stickleback (Gasterosteus aculeatus). We used a mesocosm experiment to directly examine the effects of ecological (fish presence and density) and evolutionary (phenotypic diversity and specialization) factors on community structure at lower trophic levels. We evaluated zooplankton biomass and composition, periphyton and phytoplankton chlorophyll-a concentration, and net primary production among treatments containing different densities and diversities of stickleback. Our results showed that both ecological and evolutionary differences in the top-predator affect different aspects of community structure and composition. Community structure, specifically the abundance of organisms at each trophic level, was affected by stickleback presence and density, whereas composition of zooplankton was influenced by stickleback diversity and specialization. Primary productivity, in terms of chlorophyll-a concentration and net primary production was affected by ecological but not evolutionary factors. Our results stress the importance of concurrently evaluating both changes in density and phenotypic diversity on the structure and composition of communities.
Highlights
Evidence that species’ phenotypic diversity and composition influence the structure of ecosystems is accumulating [1,2,3,4,5]
We examine the community-wide effects of a top predator, the three-spine stickleback (Gasterosteus aculeatus), on organisms at lower trophic levels that result from its presence and density and its specialization and speciation
We examine whether zooplankton abundance and composition, benthic and limnetic chlorophyll-a concentration and dissolved oxygen were affected by changes in stickleback ecology and evolution concurrently
Summary
Evidence that species’ phenotypic diversity and composition influence the structure of ecosystems is accumulating [1,2,3,4,5]. Increasing evidence for rapid evolution over the order of a few generations [6,8,9,10,11,12] has made it clear that ecological and evolutionary time scales overlap broadly [6,9,13,14,15,16], and that both ecological and evolutionary factors can have strong effects on communities, even over short periods of time. Ecological studies show how predator presence and density influence lower trophic levels [17,18,19,20,21]. A few studies have further characterized the dynamic feedback loops between evolutionary diversification and ecosystem properties, such as community structure and organization [3,9,25,26]
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