COS 181-1 - The center-periphery hypothesis revisited: a meta-analysis

Background/Question/Methods

The center-periphery hypothesis suggests that species are more abundant, demographically more performant, or genetically more diverse at the center of their range than at the periphery. Unsuitable environmental conditions and resources are expected to be the limiting factors shaping species performance and genetic variation in peripheral populations. Recent syntheses showed that most studies failed to find support for the center-periphery hypothesis. However, because these syntheses used a vote-counting approach, thus failing to account for between study variation in precision, their conclusions may be biased toward large sample size studies.





To correct for study level precision, we conducted a Bayesian meta-analysis with phylogenetic correction to test the center-periphery hypothesis using > 200 studies conducted over half a century (1968-2020). We tested for the global support of the hypothesis that in species abundance, population growth rate and genetic diversity decrease from range center to periphery. We also quantified the moderating effects of species life-history strategies and dispersal mode.

Results/Conclusions

We found no general support for the center-periphery hypothesis. When corrected for study level precision, species abundance, population growth rate, and genetic diversity were all similar across distribution ranges. This conclusion was robust to phylogenetic relatedness between species included in our meta-regression. However, we found high heterogeneity in studies effect sizes highlighting the moderate influence of species life-history strategies and dispersal mode on the likelihood of center-periphery differences in species performance. These conclusions were strong to publication bias with studies that have adequate sample size and precision were rare in our dataset.





Our study questions the generality of the center-periphery hypothesis for most taxa. Such lack of support demonstrates that common approach that test the effect of geographical position on species abundance or population performance is sub-optimal. Geographical centers and periphery only matter when they coincide with ecological niche centers and periphery.