Data from: Ecogeographic isolation and speciation in the genus Mimulus

Despite a long history of examining the geographic context of speciation,
differences in geographic range have rarely been considered a legitimate
isolating mechanism. This likely results from the complex relationship
between historical and ecological processes in determining the spatial
distribution of species. Ecogeographic isolation is the proportion of
geographic isolation that results from genetically based ecological
differences between taxa and should therefore be measured as an isolating
mechanism under the biological species concept. In this study, species
distribution modeling was used to evaluate the potential ranges of 12
recently diverged pairs of species in the genus Mimulus. Variation in the
distribution models showed that these species differ significantly in the
niches they occupy. These differences result in substantial ecogeographic
isolation, with an average strength of 0.67, revealing that, on average,
Mimulus species exhibit only 33% overlap in the extent of suitable habitat
with their closest relatives. Because prezygotic barriers act early in the
life cycle of organisms, this strong barrier has the potential to
contribute greatly to the total isolation experienced between diverging
species. Therefore, ecogeographic isolation appears to play an important
role in Mimulus, and estimating the strength of this barrier is essential
to our general understanding of speciation.