Article

Case studies and mathematical models of ecological speciation. 1. Cichlids in a crater

Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA.
Molecular Ecology (Impact Factor: 6.49). 08/2007; 16(14):2893-909. DOI: 10.1111/j.1365-294X.2007.03305.x
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ABSTRACT A recent study of a pair of sympatric species of cichlids in Lake Apoyo in Nicaragua is viewed as providing probably one of the most convincing examples of sympatric speciation to date. Here, we describe and study a stochastic, individual-based, explicit genetic model tailored for this cichlid system. Our results show that relatively rapid (<20,000 generations) colonization of a new ecological niche and (sympatric or parapatric) speciation via local adaptation and divergence in habitat and mating preferences are theoretically plausible if: (i) the number of loci underlying the traits controlling local adaptation, and habitat and mating preferences is small; (ii) the strength of selection for local adaptation is intermediate; (iii) the carrying capacity of the population is intermediate; and (iv) the effects of the loci influencing nonrandom mating are strong. We discuss patterns and timescales of ecological speciation identified by our model, and we highlight important parameters and features that need to be studied empirically to provide information that can be used to improve the biological realism and power of mathematical models of ecological speciation.

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    • "Second, this genetically based (i.e., heritable) divergence generates some degree of reproductive isolation between the populations, for instance through performance tradeoffs between the habitats (Hendry 2004; Nosil et al. 2005; Thibert-Plante and Hendry 2009), or divergence in reproductive behavior (Coyne and Orr 2004; Ritchie 2007; Maan and Seehausen 2011; Thibert-Plante and Gavrilets 2013). Although it is debatable how fast reproductive isolation through this pathway can emerge (Hendry et al. 2007; Gavrilets et al. 2007; Nosil 2012), selection over multiple generations is certainly needed to achieve the underlying genetic divergence—even when selection is strong and genetic variation is abundant. However, a faster pathway to speciation can occur when the exposure to ecologically different habitats directly causes divergence between populations through phenotypic "
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    Evolutionary Biology 05/2015; DOI:10.1007/s11692-015-9327-6 · 3.27 Impact Factor
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    • "Understanding local adaptation and speciation therefore requires inferences about the biogeography and past demography of populations, factors that may have changed substantially over the course of speciation (Hewitt 2011; Abbott et al. 2013). For example, speciation might be promoted by alternating cycles of separation by geographical barriers and secondary contact (Bierne et al. 2011), or local adaptation might be achieved more readily with some spatial arrangements of habitats than with others (Gavrilets et al. 2007). "
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    • "Instead, this finding may be, in part, a result of our tendency to name species only with clear and definable morphological characters (Rocha & Bowen, 2008; see 'Intraspecific Comparisons', below). Moreover, several lines of evidence indicate that isolation neither has to be absolute nor of long duration for speciation to occur (Gavrilets et al., 2007; Rocha & Bowen, 2008). Selection driven by ecological factors could accelerate divergence despite gene flow or continue generating divergence that began in isolation. "
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