Our research identifies key dimensions of biodiversity that hold important predictive power. These dimensions allow us to create generalizable and sound forecasts of the implications of global change.
Patterns and processes of biodiversity dynamics
The nature and extent of ecological assemblages remains a matter of controversy. Our work brings the field closer to consensus through the quantification of the multi-faceted nature of biodiversity, from traits to species to community-wide metrics of diversity.
Biodiversity change across scales
Our research program is grounded in the principles of scale dependence, where we carefully consider spatial, temporal, taxonomic, and trait-measurement scales. By acknowledging the roles of scale, we can achieve a comprehensive understanding of ecological patterns and processes.
Effects of global change on biodiversity
Biodiversity faces escalating threats due to global change, yet the full extent of the consequences is not understood. We unravel the implications of shifting climatic conditions on the distributions and phenology of organisms, as well as the subsequent reorganization of ecological communities.
The findings suggest that in the Eastern United States, resident birds, like the Northern cardinal, have a wider array of functional characteristics than migratory birds.
Using recent fine spatial and temporal resolution data from eBird, we investigated—for the first time—how seasonal bird migration shapes community-level patterns across North America (Jarzyna and Stagge 2023). We documented stark decoupling of seasonal signatures of avian taxonomic and functional diversity, particularly pronounced in the eastern US, where functional richness peaked in winter despite seasonal loss of species.
We are now following up on this study by investigating (1) how species-level and assemblage-level functional uniqueness differs between breeding and wintering seasons, and between resident and migratory birds, across the entire globe and (2) whether climatic oscillations such as ENSO or NAO play a role in the uncovered seasonal patterns of avian diversity.
For example, we found that changes in breeding bird assemblages differed from those of wintering avifauna. While breeding birds have undergone increasing functional homogenization over a 50-year time period (Jarzyna and Jetz 2017), functional reorganization of wintering avifauna has been marked by a north-south gradient, wherein assemblages in the northern US saw strong contractions of the functional space and increases in functional evenness and orginality, while the southern US saw much smaller contractions of the functional space and stasis in other components of functional diversity (Quimbayo et al. 2024).
We also found that these shifts in functional diversity were underlined by significant reshuffling in trait composition. For breeding birds, traits such as scavenging, vertebrate, and plant diets became more prevalent while others such as invertebrate and granivorous diets declined (Jarzyna and Jetz 2018). Wintering birds showed somewhat different patterns in trait reshuffling, with both invertebrate and vertebrate diets in decline (Quimbayo et al. 2024).
We are now following up on these studies to understand how spatial and temporal resolution affects measurements of biodiversity change. Specifically, we are investigating scale dependence of decadal change in taxonomic and functional composition for both breeding and wintering avifauna.
Using the fossil record for the late Quaternary (~past 26,000 years), we showed opposing temporal trends in functional diversity for small mammal communities at two sites in Europe and North America (VanBuren and Jarzyna 2022). Despite these contrasting trends in mammalian biodiversity, consistent trait-environment relationships emerged, wherein increases in temperature were associated with increases in nocturnal activity and decreases in body mass, while changes in vegetation structure led to greater dietary diversity.
This work highlighted the utility of trait-based approaches and varied geographic settings to find common trait-environment relationships among seemingly disparate community- and ecosystem-level responses to environmental change. We are now building on this initial work by investigating spatiotemporal variation of community assembly processes across the late Quaternary in North America, for which we will leverage the small mammal fossil record publicly available through the Neotoma Paleoecology Database, recent advances in simulations, and sophisticated statistical modeling.
By adopting the multi-faceted definition of biodiversity, we are challenging traditional paradigms and expanding our understanding of how ecological communities respond to various drivers and stressors. Our work also highlights the need for more nuanced approaches - ones that account for different spatial and temporal scales as well as taxonomic and trait resolutions.
