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

Abstract

When prey experience size‐based harvesting by predators, they are not only subject to selection due to larger individuals being preferentially harvested but also selection due to reductions in population density. Density‐dependent selection represents one of the most basic interactions between ecology and evolution. Yet, the reduction in density associated with exploitation has not been tested as a possible driving force of observed evolutionary changes in populations harvested size‐dependently. Using an artificial selection experiment with a mixture of Daphnia clones, we partition the evolutionary effects of size‐based harvesting into the effects of removing large individuals and the effects of lowering the population density. We show that both size selection and density‐dependent selection are significant drivers of life‐history evolution. Importantly, these drivers affected different life‐history traits with size‐selective harvesting selecting for slower juvenile growth rates and a larger size at maturity, and low‐density selecting for reduced reproductive output.

Plant spatial aggregation modulates the interplay between plant competition and pollinator attraction with contrasting outcomes of plant fitness

“…This connection highlights the fact that the fate on individual reproductive success and therefore the persistence of populations is not only a matter of the degree of temporal autocorrelation (e.g. Lyberger et al, 2021;Martinović et al, 2021) but also the degree of spatial autocorrelation. However, the spatial effects here documented are rare, and therefore, we call for a need to better integrate observational data with solid theory that connect plant-pollinator systems with multiple trophic interactions in a more comprehensive framework of plant population dynamics.…”

Plant spatial aggregation modulates the interplay between plant competition and pollinator attraction with contrasting outcomes of plant fitness

“…Such correlation in conspecific individuals across scales connects pollinator attraction, and therefore the mutualistic effect of floral visits (Ghazoul, 2006;Bruninga-Socolar and Branam, 2022;de Jager et al, 2022), with the negative competitive effect of dense local neighborhoods (Albor et al, 2019;Underwood et al, 2020). This connection highlights the fact that individual reproductive success, and therefore the persistence of populations, is a matter of not only the degree of temporal autocorrelation (e.g., Lyberger et al, 2021;Martinović et al, 2021) but also the degree of spatial autocorrelation. However, the spatial effects documented here are little explored in other systems, and therefore, we point out a need to better integrate observational data with solid theory that connects plant-pollinator systems with multiple trophic interactions in a more comprehensive framework of plant population dynamics.…”