ScienceDaily (Jan. 5, 2008) — Under which circumstances is sympatric speciation possible? An answer to this long-standing question of evolutionary biology has turned out to be challenging. In particular, models for the evolution of assortative mating under frequency-dependent disruptive selection necessarily depend on a large number of ecological and genetic factors.

For this reason, most previous approaches to this issue depend on individual-based simulations. However, simulation studies with only slightly different assumptions have come to wildly different conclusions, making it hard to generalize results and leading to fierce debate.

In a recent study Pleuni Pennings and her coworkers chose a different approach. They started out from a widely cited simulation model by Ulf Dieckmann and Michael Doebeli, who investigated sympatric speciation driven by resource competition. They then simplified the assumptions of this model to make it mathematically tractable. While retaining each of the crucial ingredients, Pennings et al. managed a completely analytical dissection of the model, something that had not appeared possible beforehand.

They found that varying the model parameters produced phenomena that had previously been described in separate papers. "This means that our model unifies insights from earlier work, which is very rewarding," says Michael Kopp, one of the authors of the study. "We also gained a better understanding of the underlying mechanisms, such as the interplay of natural and sexual selection."

The study,  "An analytically tractable model for competitive speciation" authored by Pleuni S. Pennings (Ludwig-Maximilians University), Michael Kopp (Ludwig-Maximilians University), Geza Meszena (Eotvos University), Ulf Dieckmann (International Institute for Applied Systems Analysis), and Joachim Hermisson (Ludwig-Maximilians University) was published in the January issue of the American Naturalist.

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