Dispersal ability and niche breadth influence interspecific variation in spider abundance and occupancy

The relationship between species local abundance and their regional
distribution (occupancy) is one of the most extensively recognised and
investigated patterns in ecology. While exceptions exist, the generally
held model is that locally abundant species also tend to be more
widespread geographically. However, there is only a limited understanding
of both the mechanisms driving this relationship, and their scale
dependency. Here we use occupancy and abundance data for 123 species of
spider from across the Canary Islands to understand how both dispersal
ability and niche breadth might mediate variation among species for local
abundance and occupancy. We test the predictions that (i) dispersal
ability explains variation among species for both abundance and occupancy,
and (ii) species with a higher degree of habitat specialisation,
reflecting more limited niche breadth, will have both higher occupancy and
abundance. We find no evidence within habitat patches for an effect of
dispersal ability on either local abundance or site occupancy, while
across all patches species with higher dispersal ability tend to occupy
more sites. Species largely restricted to laurel forests have higher
abundance than species with broader niche breadth, but similar
occupancy. The study revealed that dispersal ability and niche
breadth were significant predictors of the abundance-occupancy
relationship, highlighting the importance of both factors for understating
patterns of abundance and occupancy among spider species.