Abstract
BackgroundThe margins of a species’ range might be located at the margins of a species’ niche, and in such cases, can be highly vulnerable to climate changes. They, however, may also undergo significant evolutionary changes due to drastic population dynamics in response to climate changes, which may increase the chances of isolation and contact among species. Such species interactions induced by climate changes could then regulate or facilitate further responses to climatic changes. We hypothesized that climate changes lead to species contacts and subsequent genetic exchanges due to differences in population dynamics at the species boundaries. We sampled two closely related Rubus species, one temperate (Rubus palmatus) and the other subtropical (R. grayanus) near their joint species boundaries in southern Japan. Coalescent analysis, based on molecular data and ecological niche modelling during the Last Glacial Maximum (LGM), were used to infer past population dynamics. At the contact zones on Yakushima (Yaku Island), where the two species are parapatrically distributed, we tested hybridization along altitudinal gradients.ResultsCoalescent analysis suggested that the southernmost populations of R. palmatus predated the LGM (~20,000 ya). Conversely, populations at the current northern limit of R. grayanus diverged relatively recently and likely represent young outposts of a northbound range shift. These population dynamics were partly supported by the ensemble forecasting of six different species distribution models. Both past and ongoing hybridizations were detected near and on Yakushima. Backcrosses and advanced-generation hybrids likely generated the clinal hybrid zones along altitudinal gradients on the island where the two species are currently parapatrically distributed.ConclusionsClimate oscillations during the Quaternary Period and the response of a species in range shifts likely led to repeated contacts with the gene pools of ecologically distinct relatives. Such species interactions, induced by climate changes, may bring new genetic material to the marginal populations where species tend to experience more extreme climatic conditions at the margins of the species distribution.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0209-9) contains supplementary material, which is available to authorized users.
Highlights
The margins of a species’ range might be located at the margins of a species’ niche, and in such cases, can be highly vulnerable to climate changes
Genetic diversity in R. palmatus and R. grayanus The partial sequences of 12 functional nuclear loci, totaling 4,944 bp in size, were obtained from 54 and 56 individuals sampled from morphologically pure populations of R. palmatus and R. grayanus, respectively, around the species boundaries (Figure 1a, Table 1 and Additional file 1: Table S1; DNA Data Bank of Japan (DDBJ):AB926443-AB927718; AB931175-AB932515; AB975184-AB975263)
We identified 196 segregating sites when both species were considered, and 137 and 62 segregating sites within R. palmatus and R. grayanus, respectively
Summary
The margins of a species’ range might be located at the margins of a species’ niche, and in such cases, can be highly vulnerable to climate changes. A meta-analysis revealed that lower latitudinal populations of a species tended to show a higher degree of divergence between populations, even after controlling for geographic distance [7] This implies that these populations at the current rear margins often persist in isolation during a species’ range shift. Because different species/populations react in different ways in response to climate changes and have ranges covering different latitudes, the rear edge of a species may, at some point, be in contact with the leading edge of another. Such environmental change may result in sympatry and be due to the interaction of once geographically isolated species at their boundaries
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
