In speciation models, the simpler the genetic basis of host preference and performance, and the more these traits are tightly linked, the more likely sympatric speciation is to occur (Fry 2003).
What's more, he says ecologists could find many more examples of sympatric speciation by studying the numerous localities around the world with similarly sharp ecological boundaries.
This simple genetic basis can also contribute to understanding the genetic architectures that are more permissive of sympatric speciation in general.
More recently several simulation models suggested that ecology-driven sympatric speciation can occur more easily than previously thought [ 40, 41] (see review for [ 42]).
Recently several authors have concluded, based on simulation studies, that sympatric speciation can more easily occur than previously thought [ 40, 41].
We hypothesize that, as genotypic canalization enables differentiation despite random mating and increases the effectiveness of assortative mating, sympatric speciation is more likely than is commonly suggested.
According to Kunz [ 6], sympatric speciation is more likely to occur in parasites than in free-living organisms, considering that the isolation of parasite populations seems to be accomplished more easily than in free-living organisms.
"Sympatric speciation could be more common than we think," he says.
Eviatar Nevo, an evolutionary biologist at the University of Haifa in Israel, thinks that sympatric speciation could be much more common than is generally believed and he says that he has found a method to help prove it.
Although gene flow at the early stages of allopatric speciation is imaginable, parapatric and sympatric speciation appears to be the more natural scenario of speciation with gene flow.
