Patterns of Species Divergence and Genetic Theories of Speciation

Singh, Ravinder

doi:10.1007/978-3-642-74474-7_8

Cited by 19 publications

(16 citation statements)

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“…Theoretical arguments (Gavrilets 1999) and additional simulations not reported here suggest that changing L and r will not strongly affect our conclusions. Note that the values of used here are somewhat higher than current estimates of the mutation rates per locus, which are typically on the order of 10 Ϫ5 (Griffiths et al 1996;Futuyma 1997), whereas the values of K are within the range of estimates of the minimum number of genes involved in reproductive isolation (Singh 1990;Wu and Palopoli 1994;Coyne and Orr 1998).…”

Section: Parametersmentioning

confidence: 77%

Patterns of Parapatric Speciation

2000

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Abstract. Geographic variation may ultimately lead to the splitting of a subdivided population into reproductively isolated units in spite of migration. Here, we consider how the waiting time until the first split and its location depend on different evolutionary factors including mutation, migration, random genetic drift, genetic architecture, and the geometric structure of the habitat. We perform large-scale, individual-based simulations using a simple model of reproductive isolation based on a classical view that reproductive isolation evolves as a by-product of genetic divergence. We show that rapid parapatric speciation on the time scale of a few hundred to a few thousand generations is plausible even when neighboring subpopulations exchange several individuals each generation. Divergent selection for local adaptation is not required for rapid speciation. Our results substantiates the claims that species with smaller range sizes (which are characterized by smaller local densities and reduced dispersal ability) should have higher speciation rates. If mutation rate is small, local abundances are low, or substantial genetic changes are required for reproductive isolation, then central populations should be the place where most splits take place. With high mutation rates, high local densities, or with moderate genetic changes sufficient for reproductive isolation, speciation events are expected to involve mainly peripheral populations.Key words. Centrifugal speciation, holey adaptive landscapes, mathematical modeling, parapatric, peripatric.Received March 19, 1999. Accepted January 27, 2000.The geographic range sizes of most species are much larger than the typical dispersal distances of individuals (or gametes). This creates an opportunity for the generation and maintenance of extensive genetic differences among geographic populations of the same species in spite of migration. Several factors contribute to these processes. Because each specific mutation is a very rare event, whereas the number of possible mutations is enormous, different mutations will appear in different geographic areas. Mani and Clarke (1990) refer to this factor as ''mutational order.'' Additional divergence will be created by stochastic factors affecting survival and reproduction, which are commonly referred to as ''genetic drift.'' Finally, variation in abiotic and biotic conditions can result in systematic differences in selection regimes that operate in different parts of the species range to augment geographic differentiation. Extensive geographic variation is well documented for most species (e.g., Endler 1977;Avise 1994). A classical example of extreme geographic differentiation are ''ring species'' (e.g., Mayr 1942Mayr , 1963Wake 1997), where genetic differences between some neighboring populations result in strong reproductive isolation.Generation of geographic variation is a necessary step in most scenarios of speciation. Here, we concentrate on parapatric speciation, that is, speciation with some gene flow between neighboring su...

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Section: Parametersmentioning

confidence: 77%

Patterns of Parapatric Speciation

2000

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“…The second generalization concerns the absolute value of which is on the order of one over the mutation rate for a subset of the loci affecting reproductive isolation for a wide range of migration rates, population sizes, intensities of selection for local adaptation, and the number of genetic changes required for reproductive isolation. Given a ''typical'' mutation rate on the order of 10 Ϫ5 Ϫ 10 Ϫ6 per locus per generation (Griffiths et al 1996;Futuyma 1998) and assuming that there are at least on the order of 10-100 genes involved in the initial stages of the evolution of reproductive isolation (Singh 1990;Wu and Palopoli 1994;Coyne and Orr 1998;Naveira and Masida 1998;Wu 2001), the duration of speciation is predicted to range between 10 3 and 10 5 generations.…”

Section: Parapatric Speciationmentioning

confidence: 99%

Perspective: Models of Speciation: What Have We Learned in 40 Years?

2003

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Abstract. Theoretical studies of speciation have been dominated by numerical simulations aiming to demonstrate that speciation in a certain scenario may occur. What is needed now is a shift in focus to identifying more general rules and patterns in the dynamics of speciation. The crucial step in achieving this goal is the development of simple and general dynamical models that can be studied not only numerically but analytically as well. I review some of the existing analytical results on speciation. I first show why the classical theories of speciation by peak shifts across adaptive valleys driven by random genetic drift run into trouble (and into what kind of trouble). Then I describe the Bateson-Dobzhansky-Muller (BDM) model of speciation that does not require overcoming selection. I describe exactly how the probability of speciation, the average waiting time to speciation, and the average duration of speciation depend on the mutation and migration rates, population size, and selection for local adaptation. The BDM model postulates a rather specific genetic architecture of reproductive isolation. I then show exactly why the genetic architecture required by the BDM model should be common in general. Next I consider the multilocus generalizations of the BDM model again concentrating on the qualitative characteristics of speciation such as the average waiting time to speciation and the average duration of speciation. Finally, I consider two models of sympatric speciation in which the conditions for sympatric speciation were found analytically. A number of important conclusions have emerged from analytical studies. Unless the population size is small and the adaptive valley is shallow, the waiting time to a stochastic transition between the adaptive peaks is extremely long. However, if transition does happen, it is very quick. Speciation can occur by mutation and random drift alone with no contribution from selection as different populations accumulate incompatible genes. The importance of mutations and drift in speciation is augmented by the general structure of adaptive landscapes. Speciation can be understood as the divergence along nearly neutral networks and holey adaptive landscapes (driven by mutation, drift, and selection for adaptation to a local biotic and/or abiotic environment) accompanied by the accumulation of reproductive isolation as a by-product. The waiting time to speciation driven by mutation and drift is typically very long. Selection for local adaptation (either acting directly on the loci underlying reproductive isolation via their pleiotropic effects or acting indirectly via establishing a genetic barrier to gene flow) can significantly decrease the waiting time to speciation. In the parapatric case the average actual duration of speciation is much shorter than the average waiting time to speciation. Speciation is expected to be triggered by changes in the environment. Once genetic changes underlying speciation start, they go to completion very rapidly. Sympatric speciation is possible if ...

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“…However, there has been no clear description of the nature of the genes that might be specifically involved in speciation. In an attempt to fill this gap, an alternative model of speciation was proposed (Singh 1990), emphasizing the role of genes affecting primary reproductive traits in the development of reproductive isolation. This idea was based on two key observations:…”

Section: The Role Of Reproductive Tract Proteins In Reproductive Isolmentioning

confidence: 99%

“…Considering species pairs from different groups may introduce a bias in an attempt to correlate divergence with reproductive isolation, as pairs of sibling species from different Drosophila groups vary considerably in their levels of genetic divergence (Ayala 1975;Singh 1990). The virilis group species has the advantage of offering, within the same group, a wide range of variation in levels of reproductive isolation (Throckmorton 1982;Coyne and Orr 1989).…”

Section: Introductionmentioning

confidence: 99%

High divergence of reproductive tract proteins and their association with postzygotic reproductive isolation in Drosophila melanogaster and Drosophila virilis group species

1995

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The possible association between gonadal protein divergence and postzygotic reproductive isolation was investigated among species of the Drosophila melanogaster and D. virilis groups. Protein divergence was scored by high-resolution two-dimensional electrophoresis (2DE). Close to 500 protein spots from gonadal tissues (testis and ovary) and nongonadal tissues (malpighian tubules and brain) were analyzed and protein divergence was calculated based on presence vs absence. Both testis and ovary proteins showed higher divergence than nongonadal proteins, and also a highly significant positive correlation with postzygotic reproductive isolation but a weaker correlation with postzygotic reproductive isolation. Particularly, a positive and significant correlation was found between proteins expressed in the testis and postzygotic reproductive isolation among closely related species such as the within-phylad species in the D. virilis group. The high levels of male-reproductive-tract protein divergence between species might be associated with F1 hybrid male sterility among closely related species. If so, a lower level of ovary protein divergence should be expected on the basis that F1 female hybrids are fully fertile. However, this is not necessarily true if relatively few genes are responsible for the reproductive isolation observed between closely related species, as recent studies seem to suggest. We suggest that the faster rate of evolution of gonadal proteins in comparison to nongonadal proteins and the association of that rate with postzygotic reproductive isolation may be the result of episodic and/or sexual selection on male and female molecular traits.

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Patterns of Species Divergence and Genetic Theories of Speciation

Cited by 19 publications

References 0 publications

Patterns of Parapatric Speciation

Patterns of Parapatric Speciation

Perspective: Models of Speciation: What Have We Learned in 40 Years?

High divergence of reproductive tract proteins and their association with postzygotic reproductive isolation in Drosophila melanogaster and Drosophila virilis group species

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