Historical contingency, niche conservatism and the tendency for some taxa to be more diverse towards the poles
Author and article information
Abstract
Successful explanations for diversity gradients should account for both the generalized tendency towards a higher tropical diversity and its exceptions. Moreover, identifying exceptions to general trends, such as the latitudinal diversity gradient can give insight into the mechanistic explanations responsible for structuring them. The Cenozoic biotic exchange of mammals across the Bering land-bridge provides an illuminating case-study. It allows comparing the diversity of clades that participated in the exchange (colonizers), whose ancestors withstood the Beringian cold temperatures, with that of the clades that did not participate (sedentaries). We find that assemblages of colonizers are more diverse towards higher latitudes, opposing the traditional latitudinal diversity gradient which is followed by sedentaries. Despite the long passage of time since this major dispersal event, the geographic distribution of colonizers is more strongly correlated to the distributions of other colonizers inhabiting a different continent than by the distribution of sedentary species. These results highlight the importance of historical migrations and dispersal in configuring present-day diversity gradients. Importantly, we also suggest that colonizers may be particularly vulnerable to projected climate change because of the predicted decrease in climate space in the extra-tropical realm where they are currently most diverse.
Cite this as
2018. Historical contingency, niche conservatism and the tendency for some taxa to be more diverse towards the poles. PeerJ Preprints 6:e26440v1 https://doi.org/10.7287/peerj.preprints.26440v1Author comment
This is a preprint submission to PeerJ Preprints.
Sections
Supplemental Information
Supplemental files including Appendices S1-S7
Appendix S1 Species list and classification.
Appendix S2 Detailed results from MEMs.
Appendix S3 Model verification.
Appendix S4 Moran’s I spatial autocorrelation analyses.
Appendix S5 Phylogenetic analyses of variation in richness-temperature slopes.
Appendix S6 Cross-predictions among phylogenetic models of climatic tolerances.
Appendix S7 Diversification analyses for the subsets of colonizers and sedentary mammal species.
Additional Information
Competing Interests
The authors declare that they have no competing interests.
Author Contributions
Ignacio Morales-Castilla conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Jonathan T Davies conceived and designed the experiments, wrote the paper, reviewed drafts of the paper.
Miguel Ángel Rodríguez conceived and designed the experiments, wrote the paper, reviewed drafts of the paper.
Data Deposition
The following information was supplied regarding data availability:
GitHub
https://github.com/MoralesCastilla/Reversed-richness/tree/master/data
Funding
I.M.-C. received support by the Fonds de Recherches du Québec - Nature et Technologies (FQRNT) programme, Projet de Recherche en Équipe and is currently supported by a Postdoctoral Fellowship by the Programa Propio de la Universidad de Alcalá. The Ministry of Economy and Competitiveness of Spain awarded a grant to M.A.R. (CGL2013-48768-P). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
