Sympatric speciation is a process by which a single species splits into two, while remaining within the same geographic region. In contrast, so called allopatric speciation takes place in geographic isolation. Sympatric speciation is often viewed as more unlikely or problematic because gene flow may impede the two incipient species to evolve reproductive isolation. We have studied another potential obstacle to this type of speciation, namely competition in combination with environmental variation.
Shortly after speciation in sympatry the two newly formed species will share the same habitat and be ecologically similar. Therefore, there are reasons to believe that one of them will go extinct due to strong interspecific competition. Our theoretical investigation revealed that a combination of weak environmental correlation and high environmental variability make diverging branches go extinct and delays of the speciation. When it eventually occurs in those cases, the population densities fluctuate wildly indicating a high extinction risk.
To find out more about our research in this area, check out:
Johansson, J. and Ripa, J. 2006. Will sympatric speciation fail due to stochastic competitive exclusion? Am Nat 168: 572–578.
Johansson, J. et al. 2010. The risk of competitive exclusion during evolutionary branching: effects of resource variability, correlation and autocorrelation. Theor Pop Biol 77:95–104.