Regional occupancy increases for widespread species but decreases for narrowly distributed species in metacommunity time series

While human activities are known to elicit rapid turnover in species composition through time, the properties of the species that increase or decrease their spatial occupancy underlying this turnover are less clear. Here, we used an extensive dataset of 238 metacommunity time series of multiple taxa spread across the globe to evaluate whether species that are more widespread (large-ranged species) differed in how they changed their site occupancy over the 10-90 years the metacommunities were monitored relative to species that are more narrowly distributed (small-ranged species). We found that on average, large-ranged species tended to increase in occupancy through time, whereas small-ranged species tended to decrease. These relationships were stronger in marine than in terrestrial and freshwater realms. However, in terrestrial regions, the directional changes in occupancy were less extreme in protected areas. Our findings provide evidence for systematic decreases in occupancy of small-ranged species, and that habitat protection could mitigate these losses in the face of environmental change. Whether a species declines under the current biodiversity crisis could partly depend on its range size. Here, the authors use replicated metacommunity data to identify global patterns in the relationship between species' range size and changes in occupancy through time.

Automated summary

Using global metacommunity data, this study found that large-ranged species tend to increase in site occupancy over time, while small-ranged species tend to decrease. This pattern is more pronounced in marine habitats, but in terrestrial regions, protected areas show less extreme changes in occupancy. These findings highlight the importance of range size in determining species declines and the potential of habitat protection in mitigating these losses under environmental change.