Interactions among quantitative traits in the course of sympatric speciation

Abstract

Sympatric speciation, the origin of two or more species from a single local population, has almost certainly been involved in formation of several species flocks, and may be fairly common in nature. The most straightforward scenario for sympatric speciation requires disruptive selection favouring two substantially different phenotypes, and consists of the evolution of reproductive isolation between them followed by the elimination of all intermediate phenotypes. Here we use the hypergeometric phenotypic model to show that sympatric speciation is possible even when fitness and mate choice depend on different quantitative traits, so that speciation must involve formation of covariance between these traits. The increase in the number of variable loci affecting fitness facilitates sympatric speciation, whereas the increase in the number of variable loci affecting mate choice has the opposite effect. These predictions may enable more cases of sympatric speciation to be identified.

Incipient allochronic speciation due to non-selective assortative mating by flowering time, mutation and genetic drift

“…Random genetic drift has previously been shown to accelerate the evolution of reproductive isolation by facilitating strong linkage disequilibrium between ecological and mating strategies (Dieckmann & Doebeli 1999;van Doorn & Weissing 2001) or fostering local adaptation to adjacent habitats differing in flowering time (Stam 1983). Previous models of sympatric speciation involved disruptive natural or sexual selection (Kondrashov & Kondrashov 1999;Drossel & McKane 2000;Doebeli & Dieckmann 2003;Bü rger et al 2006;Doebeli et al 2007;Gavrilets & Vose 2007;Leimar et al 2008). In those models, disruptive selection and reproductive isolation are caused by resource competition among similar phenotypes, displacement into distinct ecological niches or selective assortative mating.…”

“…In contrast to previous models of sympatric speciation based on disruptive sexual selection ( Nei et al 1983;Wu 1985;Higashi et al 1999;Kondrashov & Kondrashov 1999;Doebeli & Dieckmann 2003), we evaluate the potential for sympatric speciation in the absence of disruptive natural or sexual selection. Our model includes neither disruptive selection caused by pollinators (e.g.…”

Heterozygote deficiencies in small lacustrine populations of brook charr Salvelinus Fontinalis Mitchill (Pisces, Salmonidae): a test of alternative hypotheses

“…Consequently, the occurrence of sympatric but differentiated populations of brook charr in our samples may have remained undetected. Although the underlying mechanisms are still debated (Diekman and Doebeli, 1999;Kondrashov and Kondrashov, 1999), intraspecific competition is believed to be one of the major causes of the divergence of sympatric populations of northern temperate lacustrine fishes (reviewed in Schluter, 2000). If intraspecific competition is increased in smaller lakes because of more limited resources, the probability and intensity of population divergence could be higher in smaller lakes, thereby explaining the observed correlation between lake size and heterozygote deficiency due to Wahlund effect.…”

Drosophila flies in “Evolution Canyon” as a model for incipient sympatric speciation

“…Several theoretical models have been proposed for evolution of premating isolation promoted by divergent ecological and sexual selections (6,(14)(15)(16)(17). However, extensive field studies on suitable experimental models are mandatory for a better understanding of this controversial scenario (8,18,19).…”

“…Is sexual isolation an incidental by-product of genetic divergence independent of whether differentiation evolved by random drift or selection? Is it selected because of its contribution to higher fitness (14)? Will reproductive isolation evolve repeatedly in independent, closely related populations subjected to divergent selection?…”