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A genetically explicit model of speciation by sensory drive within a continuous population in aquatic environments.

Kawata M, Shoji A, Kawamura S, Seehausen O - BMC Evol. Biol. (2007)

Bottom Line: In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation, whereas we did not observe speciation when peak absorption evolved by stepwise mutations with small effect.The results suggest that speciation can occur where environmental gradients create divergent selection on sensory modalities that are used in mate choice.Evidence for such gradients exists from several animal groups, and from freshwater and marine fishes in particular.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, Graduate School of Sciences, Tohoku University, Sendai, Japan. kawata@mail.tains.tohoku.ac.jp

ABSTRACT

Background: The sensory drive hypothesis predicts that divergent sensory adaptation in different habitats may lead to premating isolation upon secondary contact of populations. Speciation by sensory drive has traditionally been treated as a special case of speciation as a byproduct of adaptation to divergent environments in geographically isolated populations. However, if habitats are heterogeneous, local adaptation in the sensory systems may cause the emergence of reproductively isolated species from a single unstructured population. In polychromatic fishes, visual sensitivity might become adapted to local ambient light regimes and the sensitivity might influence female preferences for male nuptial color. In this paper, we investigate the possibility of speciation by sensory drive as a byproduct of divergent visual adaptation within a single initially unstructured population. We use models based on explicit genetic mechanisms for color vision and nuptial coloration.

Results: We show that in simulations in which the adaptive evolution of visual pigments and color perception are explicitly modeled, sensory drive can promote speciation along a short selection gradient within a continuous habitat and population. We assumed that color perception evolves to adapt to the modal light environment that individuals experience and that females prefer to mate with males whose nuptial color they are most sensitive to. In our simulations color perception depends on the absorption spectra of an individual's visual pigments. Speciation occurred most frequently when the steepness of the environmental light gradient was intermediate and dispersal distance of offspring was relatively small. In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation, whereas we did not observe speciation when peak absorption evolved by stepwise mutations with small effect.

Conclusion: The results suggest that speciation can occur where environmental gradients create divergent selection on sensory modalities that are used in mate choice. Evidence for such gradients exists from several animal groups, and from freshwater and marine fishes in particular. The probability of speciation in a continuous population under such conditions may then critically depend on the genetic architecture of perceptual adaptation and female mate choice.

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The simulation area and supposed habitat size. The simulation was conducted in 1000 × 1000 square area. This was assumed as a slope of the bottom of a lake.
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Figure 4: The simulation area and supposed habitat size. The simulation was conducted in 1000 × 1000 square area. This was assumed as a slope of the bottom of a lake.

Mentions: Our results provide several new and testable predictions for when sensory drive is likely or unlikely to cause speciation within a continuous population. In our simulations speciation occurred most frequently when environmental light gradients were of intermediate steepness and dispersal distance of offspring was relatively small. Because we kept the length of the environmental light gradient (GE) constant, the variation in steepness of GE was synonymous with variation in the magnitude of the selection differential between the ends of the cline (e.g. the depth difference between the ends of the y axis, see Fig. 4). Lack of speciation at GE < 0.1 was likely due to a too small selection differential. Lack of speciation at larger dispersal distances is due to the breakdown of local adaptation (Hendry et al. 2001). The steeper the selection gradient the smaller the dispersal distance that is sufficient to break down local adaptation. This may explain the counterintuitive result that speciation is not common when the selection gradient is very steep. In addition, small dispersal distances cause spatial clumping of related genotypes, which may promote the establishment of linkage disequilibrium between mating preferences and male secondary sexual traits and hence speciation [71,76].


A genetically explicit model of speciation by sensory drive within a continuous population in aquatic environments.

Kawata M, Shoji A, Kawamura S, Seehausen O - BMC Evol. Biol. (2007)

The simulation area and supposed habitat size. The simulation was conducted in 1000 × 1000 square area. This was assumed as a slope of the bottom of a lake.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1941727&req=5

Figure 4: The simulation area and supposed habitat size. The simulation was conducted in 1000 × 1000 square area. This was assumed as a slope of the bottom of a lake.
Mentions: Our results provide several new and testable predictions for when sensory drive is likely or unlikely to cause speciation within a continuous population. In our simulations speciation occurred most frequently when environmental light gradients were of intermediate steepness and dispersal distance of offspring was relatively small. Because we kept the length of the environmental light gradient (GE) constant, the variation in steepness of GE was synonymous with variation in the magnitude of the selection differential between the ends of the cline (e.g. the depth difference between the ends of the y axis, see Fig. 4). Lack of speciation at GE < 0.1 was likely due to a too small selection differential. Lack of speciation at larger dispersal distances is due to the breakdown of local adaptation (Hendry et al. 2001). The steeper the selection gradient the smaller the dispersal distance that is sufficient to break down local adaptation. This may explain the counterintuitive result that speciation is not common when the selection gradient is very steep. In addition, small dispersal distances cause spatial clumping of related genotypes, which may promote the establishment of linkage disequilibrium between mating preferences and male secondary sexual traits and hence speciation [71,76].

Bottom Line: In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation, whereas we did not observe speciation when peak absorption evolved by stepwise mutations with small effect.The results suggest that speciation can occur where environmental gradients create divergent selection on sensory modalities that are used in mate choice.Evidence for such gradients exists from several animal groups, and from freshwater and marine fishes in particular.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, Graduate School of Sciences, Tohoku University, Sendai, Japan. kawata@mail.tains.tohoku.ac.jp

ABSTRACT

Background: The sensory drive hypothesis predicts that divergent sensory adaptation in different habitats may lead to premating isolation upon secondary contact of populations. Speciation by sensory drive has traditionally been treated as a special case of speciation as a byproduct of adaptation to divergent environments in geographically isolated populations. However, if habitats are heterogeneous, local adaptation in the sensory systems may cause the emergence of reproductively isolated species from a single unstructured population. In polychromatic fishes, visual sensitivity might become adapted to local ambient light regimes and the sensitivity might influence female preferences for male nuptial color. In this paper, we investigate the possibility of speciation by sensory drive as a byproduct of divergent visual adaptation within a single initially unstructured population. We use models based on explicit genetic mechanisms for color vision and nuptial coloration.

Results: We show that in simulations in which the adaptive evolution of visual pigments and color perception are explicitly modeled, sensory drive can promote speciation along a short selection gradient within a continuous habitat and population. We assumed that color perception evolves to adapt to the modal light environment that individuals experience and that females prefer to mate with males whose nuptial color they are most sensitive to. In our simulations color perception depends on the absorption spectra of an individual's visual pigments. Speciation occurred most frequently when the steepness of the environmental light gradient was intermediate and dispersal distance of offspring was relatively small. In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation, whereas we did not observe speciation when peak absorption evolved by stepwise mutations with small effect.

Conclusion: The results suggest that speciation can occur where environmental gradients create divergent selection on sensory modalities that are used in mate choice. Evidence for such gradients exists from several animal groups, and from freshwater and marine fishes in particular. The probability of speciation in a continuous population under such conditions may then critically depend on the genetic architecture of perceptual adaptation and female mate choice.

Show MeSH
Related in: MedlinePlus