Biodiversity change under adaptive community dynamics

Abstract

Compositional change is a ubiquitous response of ecological communities to environmental drivers of global change, but is often regarded as evidence of declining "biotic integrity" relative to historical baselines. Adaptive compositional change, however, is a foundational idea in evolutionary biology, whereby changes in gene frequencies within species boost population-level fitness, allowing populations to persist as the environment changes. Here, we present an analogous idea for ecological communities based on core concepts of fitness and selection. Changes in community composition (i.e., frequencies of genetic differences among species) in response to environmental change should normally increase the average fitnessof community members. We refer to compositional changes that improve the functional match, or "fit," between organisms' traits and their environment as adaptive community dynamics. Environmental change (e.g., land-use change) commonly reduces the fit between antecedent communities and new environments. Subsequent change in community composition in response to environmental changes, however, should normally increase community-level fit, as the success of at least some constituent species increases. We argue that adaptive community dynamics are likely to improve or maintain ecosystem function (e.g., by maintaining productivity). Adaptive community responses may simultaneously produce some changes that are considered societally desirable (e.g., increased carbon storage) and others that are undesirable (e.g., declines of certain species), just as evolutionary responses within species may be deemed desirable (e.g., evolutionary rescue of an endangered species) or undesirable (e.g., enhanced virulence of an agricultural pest).When assessing possible management interventions, it is important to distinguish between drivers of environmental change (e.g., undesired climate warming) and adaptive community responses, which may generate some desirable outcomes. Efforts to facilitate, accept, or resist ecological change require separate consideration of drivers and responses, and may highlight the need to reconsider preferences for historical baseline communities over communities that are better adapted to the new conditions.

Widespread shifts in body size within populations and assemblages

“…To examine these scenarios, we used time series that recorded organism abundance and body size (biomass) data in the field and quantified the contribution of both components, compositional and within-species body size changes, to change in body size distributions across taxa. Specifically, we collated 5025 assemblages over 60 years ( 17 ), a time period of intensification of anthropogenic selection forces on the biosphere ( 18 ). These time series ranged from 5 to 56 years of surveys and covered 4292 species within six taxonomic groups (1971 fish species, 1201 plants species, 628 invertebrate species, 66 mammals species, 33 herpetofauna species, and 393 marine benthic organisms) from communities distributed across multiple regions of the world (fig.…”

Correlated biodiversity change between plant and insect assemblages resurveyed after 80 years across a dynamic habitat mosaic

“…Soil moisture (EIV F) and light availability (EIV L) were important predictors of species composition across taxa within sampling periods, and the study system has undergone widespread hydrological change and varying degrees of vegetative succession between the sampling periods (Carroll et al, 2018). Abiotic factors are important drivers of biodiversity change in general (Mutshinda et al, 2009; Vellend, 2016), as species adapted to particular environmental conditions respond to environmental change (Carroll et al, 2023), and hydrology and vegetation structure in particular are both important determinants of plant and invertebrate community composition (De Szalay & Resh, 2000; Silvertown et al, 2015). Effects of environmentally induced selection were further supported by congruent species richness differences at the sampling compartment level, where adjusting for environmental factors broadly reduced model estimates of temporal congruence in species richness differences.…”

Geographic and temporal distance–decay relationships across taxa

“…Second, we compared community composition for any given year to the first year of sampling. This means that temporal distance decay would be observed so long as the community is shifting away from the state it was at first sampling (for better or worse; Carroll et al 2023). See the Supporting information for the results of these two approaches.…”