Abstract
Little is known about how mutualistic interactions affect the distribution of species richness on broad geographic scales. It has been predicted that the richness of species involved in obligate mutualisms should be positively associated across their range. Whereas, if mutualisms are facilitative, the distribution of mutualists should be correlated with other factors. This study is the first study to compare the co-distribution of mutualist species in general and seed dispersal mutualisms specifically. We used geographic distributions of plant and animal mutualists to investigate the co-distribution and patterns of seed dispersal mutualisms. We found the mutualism between dispersers and plants does not account for the distribution of either group. In fact, there is a mismatch of richness between plants and the animals that disperse their seeds. Environmental factors are better predictors of both animal distribution and seed dispersal mutualisms across North America.
Statement of authorship JD, CM, and SV conceived the original project idea. Plant data were compiled and analyzed by CM and SV, and JD compiled animal and environmental data. JD standardized and formatted all geographical data, and JD and CM performed all statistical analyses. JD wrote the first draft of the manuscript, and all authors contributed significantly to the revisions.
