Abstract
Although karyotypic differences between species have long been recognized, the question of whether these mutations play a causal role in speciation remains unanswered. This is because most models of chromosomal speciation focus on underdominance, which presents a theoretical paradox in that the strength of an underdominant barrier is inversely proportional to its fixation probability. To counter this problem, a new model has been proposed that focuses on the modification of effective recombination rates, whereby rearrangements facilitate the build up of linkage disequilibrium in the presence of gene flow. This model is discussed, along with new supporting data from the Solanaceae.