Linking intraspecific trait variation to community abundance dynamics improves ecological predictability by revealing a growth–defence trade‐off

Abstract

Abstract1. Intraspecific trait change, including altered behaviour or morphology, can drive temporal variation in interspecific interactions and population dynamics. In turn, variation in species' interactions and densities can alter the strength and direction of trait change. The resulting feedback between species' traits and abundance permits a wide range of community dynamics that would not be expected from ecological theories purely based on species abundances. Despite the theoretical importance of these interrelated processes, unambiguous experimental evidence of how intraspecific trait variation modifies species interactions and population dynamics and how this feeds back to influence trait variation is currently required.2. We investigate the role of trait-mediated demography in determining community dynamics and examine how ecological interactions influence trait change. We concurrently monitored the dynamics of community abundances and individual traits in an experimental microbial predator-prey-resource system. Using this data, we parameterised a trait-dependent community model to identify key ecologically relevant traits and to link trait dynamics with those of species abundances.3. Our results provide clear evidence of a feedback between trait change, demographic rates and species dynamics. The inclusion of trait-abundance feedbacks into our population model improved the predictability of ecological dynamics from r 2 of 34% to 57% and confirmed theoretical expectations of density-dependent population growth and species interactions in the system. 4. Additionally, our model revealed that the feedbacks were underpinned by a tradeoff between population growth and anti-predatory defence. High predator abundance was linked to a reduction in prey body size. This prey size decrease was associated with a reduction in its rate of consumption by predators and a decrease in its resource consumption.5. Modelling trait-abundance feedbacks allowed us to pinpoint the underlying life history trade-off which links trait and abundance dynamics. These results show that accounting for trait-abundance feedbacks has the potential to improve understanding and predictability of ecological dynamics. | 497Functional Ecology GRIFFITHS eT al. | INTRODUCTIONTrait variation within species is increasingly recognised as having important impacts on the population dynamics of natural communities (Berg & Ellers, 2010;Schoener, 2011). Such variation can be driven by evolutionary selection pressures favouring certain heritable traits (Kasada, Yamamichi, & Yoshida, 2014;Thompson, 1998;Yoshida, Hairston, & Ellner, 2004). Alternatively, trait variation can be caused by phenotypic plasticity, when a single genotype produces different phenotypes under differing environments (Agrawal, 2001;Cortez, 2011;Fordyce, 2006;Tollrian & Harvell, 1999). For example, the timing of life history events or the allocation of resources to growth and defence may depend on the density of predators and resources and on environmental conditions (Finlay, 1977;Lam...

Responses of zooplankton body size and community trophic structure to temperature change in a subtropical reservoir

“…The importance of intra-versus interspecific trait variation has been highlighted in aquatic ecosystems (Brans et al, 2017;Griffiths et al, 2018;Lemmens et al, 2017) and has been shown to play an important role in shaping the community trophic structure (Bolnick et al, 2011;Gibert & DeLong, 2017). Here, we assessed how intra-(ITV) versus intertaxonomic (TS) variations contributed to changes in community body size and trophic structure of zooplankton.…”

“…Both intraspecific and interspecific variation can alter community trophic structure and dynamics (Bolnick et al, ; Dézerald et al, ; Griffiths, Petchey, Pennekamp, & Childs, ; Newsome et al, ). For example, a study by Lemmens et al () found that the differences in community isotopic niche space of fish were largely determined by intraspecific variation.…”

“…For example, a study by Lemmens et al () found that the differences in community isotopic niche space of fish were largely determined by intraspecific variation. In another example, Griffiths et al () found that a strong coupling between resources, ecological predator‐prey interactions, and intraspecific trait (i.e., body size) variation influenced community stability in experimental microcosms of protist communities. This indicates that a complex interplay exists between intra‐ and interspecific processes in temporal community dynamics.…”

“…Understanding the contribution of intraspecific and interspecific variation on trophic structure of consumers is important but still largely unknown (Griffiths et al, 2018;Laughlin & Messier, 2015;Lin et al, 2017). Community difference can be partitioned into species sorting (SS), intraspecific trait variation (ITV), and species turnover (ST) using the Price equation (Price, 1970).…”

Large Underestimation of Intraspecific Trait Variation and Its Improvements

“…Intraspecific trait variation (ITV) is the overall difference in traits values among conspecific individuals in one or more traits, such as height, specific leaf area, and wood density (Albert et al, 2011). Such variation widely exists in nature (Darwin, 1859;Siefert et al, 2015) and has large ecological effects on population dynamics (Agashe, 2009;Abbott and Stachowicz, 2016), community assembly (Siefert and Ritchie, 2016;Griffiths et al, 2018), and ecosystem functioning (Bukowski and Petermann, 2014;Souza et al, 2017). Because of its wide ranging ecological consequences, the ecological effects of ITV and the extent of ITV are increasingly attracting research attention (Des et al, 2018).…”