Limits...
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.Both past and ongoing hybridizations were detected near and on Yakushima.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.

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

Related in: MedlinePlus

Locations of sampled populations and species distributions. (a) Open circles represent Rubus palmatus sample locations (pKG, pBS, pEB, pKD, and pYK), and closed circles indicate sample locations of R. grayanus (gOK, gAM, gYK, and gTN). R. palmatus southern limits (solid line) and R. grayanus northern limits (dashed line) are shown. Geographic coordinates and altitudes are given in Table 1. (b) Sampled populations along altitudes on Yakushima, where the two species’ distributions merged, are indicated as shaded squares (ab1, ab2, ab3, ab4, ab5, pYK* on Anbo Lane, and sr1, sr2, sr3, sr4 on Shiratani Lane). Some individuals from the pYK population (pYK*) were located along Anbo Lane at high altitude and included in the analysis of the contact zones. The dashed line indicates the approximate sampling areas for pYK and gYK populations.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig1: Locations of sampled populations and species distributions. (a) Open circles represent Rubus palmatus sample locations (pKG, pBS, pEB, pKD, and pYK), and closed circles indicate sample locations of R. grayanus (gOK, gAM, gYK, and gTN). R. palmatus southern limits (solid line) and R. grayanus northern limits (dashed line) are shown. Geographic coordinates and altitudes are given in Table 1. (b) Sampled populations along altitudes on Yakushima, where the two species’ distributions merged, are indicated as shaded squares (ab1, ab2, ab3, ab4, ab5, pYK* on Anbo Lane, and sr1, sr2, sr3, sr4 on Shiratani Lane). Some individuals from the pYK population (pYK*) were located along Anbo Lane at high altitude and included in the analysis of the contact zones. The dashed line indicates the approximate sampling areas for pYK and gYK populations.

Mentions: 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; DDBJ:AB926443-AB927718; AB931175-AB932515; AB975184-AB975263). Sequence reads contained 106 bp of a non-coding region in the COP1-homolog gene and 92 bp in the GSTF-homolog gene. We identified 196 segregating sites when both species were considered, and 137 and 62 segregating sites within R. palmatus and R. grayanus, respectively. A total of 12 fixed sites between species in total were found in four loci (Additional file 1: Table S1). The eight other loci had only shared polymorphisms. The Wright fixation index, FST, between the two species varied among loci, but was generally high (FST =0.371-0.859).Figure 1


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)

Locations of sampled populations and species distributions. (a) Open circles represent Rubus palmatus sample locations (pKG, pBS, pEB, pKD, and pYK), and closed circles indicate sample locations of R. grayanus (gOK, gAM, gYK, and gTN). R. palmatus southern limits (solid line) and R. grayanus northern limits (dashed line) are shown. Geographic coordinates and altitudes are given in Table 1. (b) Sampled populations along altitudes on Yakushima, where the two species’ distributions merged, are indicated as shaded squares (ab1, ab2, ab3, ab4, ab5, pYK* on Anbo Lane, and sr1, sr2, sr3, sr4 on Shiratani Lane). Some individuals from the pYK population (pYK*) were located along Anbo Lane at high altitude and included in the analysis of the contact zones. The dashed line indicates the approximate sampling areas for pYK and gYK populations.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig1: Locations of sampled populations and species distributions. (a) Open circles represent Rubus palmatus sample locations (pKG, pBS, pEB, pKD, and pYK), and closed circles indicate sample locations of R. grayanus (gOK, gAM, gYK, and gTN). R. palmatus southern limits (solid line) and R. grayanus northern limits (dashed line) are shown. Geographic coordinates and altitudes are given in Table 1. (b) Sampled populations along altitudes on Yakushima, where the two species’ distributions merged, are indicated as shaded squares (ab1, ab2, ab3, ab4, ab5, pYK* on Anbo Lane, and sr1, sr2, sr3, sr4 on Shiratani Lane). Some individuals from the pYK population (pYK*) were located along Anbo Lane at high altitude and included in the analysis of the contact zones. The dashed line indicates the approximate sampling areas for pYK and gYK populations.
Mentions: 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; DDBJ:AB926443-AB927718; AB931175-AB932515; AB975184-AB975263). Sequence reads contained 106 bp of a non-coding region in the COP1-homolog gene and 92 bp in the GSTF-homolog gene. We identified 196 segregating sites when both species were considered, and 137 and 62 segregating sites within R. palmatus and R. grayanus, respectively. A total of 12 fixed sites between species in total were found in four loci (Additional file 1: Table S1). The eight other loci had only shared polymorphisms. The Wright fixation index, FST, between the two species varied among loci, but was generally high (FST =0.371-0.859).Figure 1

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.Both past and ongoing hybridizations were detected near and on Yakushima.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.

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
Related in: MedlinePlus