Habitat-trait interactions that control response to climate change: North American ground beetles (Carabidae)

Background/Question/Methods

As one of the most diverse and economically important families on earth, the ground beetles (Carabidae) are viewed as a key barometer of climate change. Recent meta-analyses provide equivocal evidence on recent abundance changes of terrestrial insects. Long time series often do not provide reliable trend estimates due to the high noise levels in sampling data. Results from individual studies do not extrapolate to regions or continents due to the dominating effects of local habitat heterogeneity on insect activity. The climate-habitat interactions (CHI) that govern responses to climate change can only be inferred where habitat-specific time series are distributed across broad climate gradients. We synthesized pitfall trap data from the National Ecological Observation Network (NEON) and additional raw data from studies across North America. We combined the abundance data with LiDAR-derived habitat characteristics (gap fraction, understory density, and surface roughness) within a generalized joint attribute model (GJAM). We quantified CHI at both the species and trait levels (e.g., body size, burrowing, running, flight, and climbing).

Results/Conclusions

Climate and local habitat variables, including changing moisture availability and the interaction between gap fraction and temperature, contribute to the local and regional trends in species abundances and community weighted mean traits. Across North America, fliers benefit from open habitats in warm and dry climates. By contrast, burrowers, climbers, runners, and diurnal species prefer warm climates beneath closed canopies. Warmer and wetter climate increase body size. Species-specific abundance changes predicted by the fitted model under Shared Socioeconomic Pathways (SSP) scenarios are governed by CHI and habitat heterogeneity. For example, the large, non-flier (Pterosichus pensylvanicus) is projected to decline across much of the continent, but the magnitude of declines are reduced or even reversed where canopies are sparse. Conversely, temperature dominates the response of the small, frequent flier (Agonoleptus conjunctus), causing projected change to be more closely linked to regional temperature changes. Our results show that habitat interactions result in site-specific community reorganization in ways that cannot be predicted by extrapolating trends from models that omit CHI.