Data from: A closer examination of the 'abundant center' hypothesis for reef fishes

Aim: The ‘abundant center’ hypothesis states that species are more
abundant at the center of their range. However, several recent large-scale
studies have failed to find evidence for such a pattern. Here we use
extensive global data of reef fishes to test the strength of the
'abundant center' pattern, and to examine variation in the
patterns across species using life history and ecological traits.
Location: Marine habitat at a global extent: from Indo-Pacific to Atlantic
reefs. Methods: We used underwater visual estimates of fish abundance,
containing 22,963 transects and 1,215 species. For each species we
calculated the slope between abundance and distance to the range center,
with the range center estimated using four different methods. We tested
whether abundance patterns differ between the range core and margins using
segmented regression. Meta-analytic methods were used to synthesize
results across species, and to test whether species traits can explain
variation in the fit to the pattern among species. Results: The method
used to define the range center had a large effect on the results.
Nevertheless, in all cases we found large variation between species.
Results of the segmented regression revealed that changes in abundance
across the range core are very small and that steep declines in abundance
happen only toward the range margins. Body size and mean abundance were
the main traits affecting the fit to the pattern across species. Main
conclusions: We find large variation across species in the fit to the
abundance center pattern. Nevertheless, we do find support for a general
pattern of a range core with high, but variable, abundance and steep
decline in abundance toward the range periphery. Thus, species do tend to
be rare at the range margins, making then sensitive to extirpation due to
both natural and anthropogenic impacts.