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The role of gene expression in ecological speciation.

Pavey SA, Collin H, Nosil P, Rogers SM - Ann. N. Y. Acad. Sci. (2010)

Bottom Line: Gene expression may be associated with ecologically important phenotypes not evident from morphology and play a role during colonization of new environments.We also find clear examples of gene expression having effects on phenotypic traits and adaptive genetic divergence, but links to the evolution of reproductive isolation itself remain indirect.The study of gene expression has promise for increasing our understanding ecological speciation, particularly when integrative approaches are applied.

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Affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada.

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An example of the effects of gene expression in two genes (bone morphogenetic protein 4, bmp4, and calmodulin, CaM) on phenotypic traits of likely importance for ecological speciation in Geospiza, Darwin's finches. (A) Evidence for divergent selection on beak depth from reconstructions of adaptive landscapes. Lines depict the expected population density of a solitary granivorous finch species on two Galápagos islands (similar results were observed on 13 other islands). Dots depict mean log beak depths of actual populations for each curve. Distinct peaks in the adaptive landscape indicate divergent selection, as supported by the observation that actual beak depths differ among populations and tend to correspond to peaks in the landscape. Thus, selection against migrants between environments and intermediate hybrids would likely cause reproductive isolation. Modified from Schluter and Grant139 and reprinted with permission of the American Society for Naturalists. (B) Summary of the evidence that bmp- and CaM -dependent signaling regulates growth along different axes of bill morphology, facilitating the evolution of distinct beak morphologies in Darwin's finches. A beak of the sharp-beaked finch reflects a basal morphology for Geospiza. Abbreviations: C, caudal; D, dorsal; R, rostral; V, ventral. Modified from Abzhanov et al.145 and reprinted with permission of Nature.
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fig03: An example of the effects of gene expression in two genes (bone morphogenetic protein 4, bmp4, and calmodulin, CaM) on phenotypic traits of likely importance for ecological speciation in Geospiza, Darwin's finches. (A) Evidence for divergent selection on beak depth from reconstructions of adaptive landscapes. Lines depict the expected population density of a solitary granivorous finch species on two Galápagos islands (similar results were observed on 13 other islands). Dots depict mean log beak depths of actual populations for each curve. Distinct peaks in the adaptive landscape indicate divergent selection, as supported by the observation that actual beak depths differ among populations and tend to correspond to peaks in the landscape. Thus, selection against migrants between environments and intermediate hybrids would likely cause reproductive isolation. Modified from Schluter and Grant139 and reprinted with permission of the American Society for Naturalists. (B) Summary of the evidence that bmp- and CaM -dependent signaling regulates growth along different axes of bill morphology, facilitating the evolution of distinct beak morphologies in Darwin's finches. A beak of the sharp-beaked finch reflects a basal morphology for Geospiza. Abbreviations: C, caudal; D, dorsal; R, rostral; V, ventral. Modified from Abzhanov et al.145 and reprinted with permission of Nature.

Mentions: Darwin's finches arose via adaptive radiation on the Galapagos Islands.138 Beak morphology diverged adaptively among populations and species in response to divergent selection stemming from competition and use of seeds of differing size and hardness.139,140 Beak morphology might also contribute to reproductive isolation via song divergence141 or due to selection against immigrants and (intermediate) hybrids.142,143 Among species, higher levels of the bone morphogenetic protein 4 (Bmp4) expression are correlated with deeper beak shapes and over-expression of Bmp4 in chick embryos altered beak development in the predicted direction.144 These results provide compelling evidence that gene expression variation from Bmp4 affects morphological divergence among species of Darwin's finches (Fig. 3). Similar results occur for another gene, calmodulin (CaM145). However, due to a lack of common garden or mapping studies, there is as of yet no evidence that heritable differences in beak morphology are affected by Bmp4 or CaM. The mutations underlying beak size differences in Darwin's finches have not been identified. Thus, although there is good evidence that regulatory changes underlie morphological divergence among species of Darwin's finches, the ultimate link between gene expression and genetically based reproductive isolation (= speciation) is yet to be made.


The role of gene expression in ecological speciation.

Pavey SA, Collin H, Nosil P, Rogers SM - Ann. N. Y. Acad. Sci. (2010)

An example of the effects of gene expression in two genes (bone morphogenetic protein 4, bmp4, and calmodulin, CaM) on phenotypic traits of likely importance for ecological speciation in Geospiza, Darwin's finches. (A) Evidence for divergent selection on beak depth from reconstructions of adaptive landscapes. Lines depict the expected population density of a solitary granivorous finch species on two Galápagos islands (similar results were observed on 13 other islands). Dots depict mean log beak depths of actual populations for each curve. Distinct peaks in the adaptive landscape indicate divergent selection, as supported by the observation that actual beak depths differ among populations and tend to correspond to peaks in the landscape. Thus, selection against migrants between environments and intermediate hybrids would likely cause reproductive isolation. Modified from Schluter and Grant139 and reprinted with permission of the American Society for Naturalists. (B) Summary of the evidence that bmp- and CaM -dependent signaling regulates growth along different axes of bill morphology, facilitating the evolution of distinct beak morphologies in Darwin's finches. A beak of the sharp-beaked finch reflects a basal morphology for Geospiza. Abbreviations: C, caudal; D, dorsal; R, rostral; V, ventral. Modified from Abzhanov et al.145 and reprinted with permission of Nature.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3066407&req=5

fig03: An example of the effects of gene expression in two genes (bone morphogenetic protein 4, bmp4, and calmodulin, CaM) on phenotypic traits of likely importance for ecological speciation in Geospiza, Darwin's finches. (A) Evidence for divergent selection on beak depth from reconstructions of adaptive landscapes. Lines depict the expected population density of a solitary granivorous finch species on two Galápagos islands (similar results were observed on 13 other islands). Dots depict mean log beak depths of actual populations for each curve. Distinct peaks in the adaptive landscape indicate divergent selection, as supported by the observation that actual beak depths differ among populations and tend to correspond to peaks in the landscape. Thus, selection against migrants between environments and intermediate hybrids would likely cause reproductive isolation. Modified from Schluter and Grant139 and reprinted with permission of the American Society for Naturalists. (B) Summary of the evidence that bmp- and CaM -dependent signaling regulates growth along different axes of bill morphology, facilitating the evolution of distinct beak morphologies in Darwin's finches. A beak of the sharp-beaked finch reflects a basal morphology for Geospiza. Abbreviations: C, caudal; D, dorsal; R, rostral; V, ventral. Modified from Abzhanov et al.145 and reprinted with permission of Nature.
Mentions: Darwin's finches arose via adaptive radiation on the Galapagos Islands.138 Beak morphology diverged adaptively among populations and species in response to divergent selection stemming from competition and use of seeds of differing size and hardness.139,140 Beak morphology might also contribute to reproductive isolation via song divergence141 or due to selection against immigrants and (intermediate) hybrids.142,143 Among species, higher levels of the bone morphogenetic protein 4 (Bmp4) expression are correlated with deeper beak shapes and over-expression of Bmp4 in chick embryos altered beak development in the predicted direction.144 These results provide compelling evidence that gene expression variation from Bmp4 affects morphological divergence among species of Darwin's finches (Fig. 3). Similar results occur for another gene, calmodulin (CaM145). However, due to a lack of common garden or mapping studies, there is as of yet no evidence that heritable differences in beak morphology are affected by Bmp4 or CaM. The mutations underlying beak size differences in Darwin's finches have not been identified. Thus, although there is good evidence that regulatory changes underlie morphological divergence among species of Darwin's finches, the ultimate link between gene expression and genetically based reproductive isolation (= speciation) is yet to be made.

Bottom Line: Gene expression may be associated with ecologically important phenotypes not evident from morphology and play a role during colonization of new environments.We also find clear examples of gene expression having effects on phenotypic traits and adaptive genetic divergence, but links to the evolution of reproductive isolation itself remain indirect.The study of gene expression has promise for increasing our understanding ecological speciation, particularly when integrative approaches are applied.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada.

Show MeSH
Related in: MedlinePlus