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Keywords:

  • Biodiversity;
  • biogeography;
  • ecophylogenetics;
  • extinction risk;
  • path analysis;
  • Rapoport's rule

Abstract

Aim

We investigated the relationship between geographic range size (GRS), longitude and latitude (Rapoport's rule) in Canadian freshwater fishes. We tested hypotheses regarding the phenotypic and phylogenetic determinants of GRS to unravel processes driving the spatial patterns of GRS in Canada. Because GRS is negatively correlated with extinction risk, we also aimed at identifying biological proxies that may be used to predict extinction risks.

Location

North-America, Canadian Shield.

Methods

We built a database combining range area, seven ecological traits, and a molecular phylogeny for native Canadian freshwater fishes. We tested latitudinal and longitudinal patterns in GRS by the mean of Pearson correlations. We combined phylogenetic generalized least squares (PGLS) models and a model selection procedure to tease apart hypotheses (and hence ecological traits) that best explained GRS in our dataset. PGLSs were also used to explore relationships between ecological traits, phylogeny, and species mid-range latitude and longitude. Partial regressions were used to determine direct and indirect relationships driving spatial patterns of GRS in Canadian freshwater fishes.

Results

There was a significant and positive correlation between GRS, latitude and longitude. According to PGLSs, three ecological traits, related to the habitat use, migratory and thermal tolerance hypotheses, were significantly correlated with GRS, mid-range longitude and mid-range latitude. Two traits related to locomotion were further related to GRS. There was no phylogenetic effect on GRS (i.e. no phylogenetic conservatism). Partial regressions revealed complex direct and indirect relationships between ecological traits, mid-range latitude, mid-range longitude and GRS.

Main conclusions

Our results show that traits related to the ability to use dispersal corridors, as well as traits directly related to mobility, are useful in understanding biodiversity patterns such as Rapoport's rule. However, because of a weak explanatory power, we conclude that using biological proxies of GRS to predict species at risk of extinction would be premature.