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Range shift and introgression of the rear and leading populations in two ecologically distinct Rubus species.

Mimura M, Mishima M, Lascoux M, Yahara T - BMC Evol. Biol. (2014)

Bottom Line: 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.Climate 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.

View Article: PubMed Central - PubMed

ABSTRACT

Background: 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. 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.

Results: Coalescent 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.

Conclusions: Climate 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.

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An ensemble forecasting of current and past distribution ofR. palmatusandR. grayanusbased on the bioclimatic variables. Sets of uncorrelated bioclimatic variables were used for each species. Probability of occurrence maps (a, b) and projected distribution of the suitable climates in the past (approx. 20,000 years ago; c, d) in R. palmatus(a, c) and R. grayanus(b, d). Dashed lines indicate the known current southern and northern limits of R. palmatus(a) and R. grayanus(b), respectively.
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Fig5: An ensemble forecasting of current and past distribution ofR. palmatusandR. grayanusbased on the bioclimatic variables. Sets of uncorrelated bioclimatic variables were used for each species. Probability of occurrence maps (a, b) and projected distribution of the suitable climates in the past (approx. 20,000 years ago; c, d) in R. palmatus(a, c) and R. grayanus(b, d). Dashed lines indicate the known current southern and northern limits of R. palmatus(a) and R. grayanus(b), respectively.

Mentions: According to Thuiller et al. [23], the area under the curve (AUC) of an ROC for true skill statistics (TSS) and Kappa statistics indicated a good-to-excellent model performance, when averaged across all replications for all modeling techniques under current climatic conditions (AUC > 0.9, TSS > 0.8, and Kappa > 0.8; Additional file 1: Table S4); the expected Kappa value of CTA for R. palmatus = 0.74. The ensemble forecasting, based on six different modeling techniques, for the distributions of R. palmatus and R. grayanus under current climates predicted slightly wider distributions compared to the known distributions (dashed line indicates the known current southern and northern limits of R. palmatus and R. grayanus in Figure 5a and b).Figure 5


Range shift and introgression of the rear and leading populations in two ecologically distinct Rubus species.

Mimura M, Mishima M, Lascoux M, Yahara T - BMC Evol. Biol. (2014)

An ensemble forecasting of current and past distribution ofR. palmatusandR. grayanusbased on the bioclimatic variables. Sets of uncorrelated bioclimatic variables were used for each species. Probability of occurrence maps (a, b) and projected distribution of the suitable climates in the past (approx. 20,000 years ago; c, d) in R. palmatus(a, c) and R. grayanus(b, d). Dashed lines indicate the known current southern and northern limits of R. palmatus(a) and R. grayanus(b), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4221717&req=5

Fig5: An ensemble forecasting of current and past distribution ofR. palmatusandR. grayanusbased on the bioclimatic variables. Sets of uncorrelated bioclimatic variables were used for each species. Probability of occurrence maps (a, b) and projected distribution of the suitable climates in the past (approx. 20,000 years ago; c, d) in R. palmatus(a, c) and R. grayanus(b, d). Dashed lines indicate the known current southern and northern limits of R. palmatus(a) and R. grayanus(b), respectively.
Mentions: According to Thuiller et al. [23], the area under the curve (AUC) of an ROC for true skill statistics (TSS) and Kappa statistics indicated a good-to-excellent model performance, when averaged across all replications for all modeling techniques under current climatic conditions (AUC > 0.9, TSS > 0.8, and Kappa > 0.8; Additional file 1: Table S4); the expected Kappa value of CTA for R. palmatus = 0.74. The ensemble forecasting, based on six different modeling techniques, for the distributions of R. palmatus and R. grayanus under current climates predicted slightly wider distributions compared to the known distributions (dashed line indicates the known current southern and northern limits of R. palmatus and R. grayanus in Figure 5a and b).Figure 5

Bottom Line: 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.Climate 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.

View Article: PubMed Central - PubMed

ABSTRACT

Background: 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. 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.

Results: Coalescent 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.

Conclusions: Climate 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.

Show MeSH