Are we analyzing speciation without prejudice?

Physical isolation has long been the null hypothesis of speciation, with exceptional evidence required to suggest speciation with gene flow Following recent persuasive theoretical support and strong empirical examples of nonal lopatric speciation, one night expect a changed view However, a review of 73 recent empirical studies shows that when allopatric speciatior is suggested a nonallopatric alternative is rarely considered, whereas the opposite is true in studies suggesting symratric speciation, indicating a biased treatment of different speciation models Although increasing support for ecological speciation suggests natural selection as the most critical component of speciation, gene flow remains an issue Methods for unbiased hypothesis testing are available, and the genetic and phylogeographic data required for appropritate tests can be generated Focus on phylogenies and functions of individual genes have revealed strong idiosyner the elements of speciation, such as single genes with possible allopatric origin that make significant contributions luring nonallopatric phases of speciation Hence a more complex picture of speciation is now emerging that will benefit from unbiased evaluation of both allopatric and sympatric mechanisms of speciation