Hypotheses about speciation by chromosomal rearrangements in the Steropleurus martorelli complex (Tettigoniodea,Orthoptera)

Four chromosomal races ranging from 2n♂ = 29 to 2n♂ = 23 have been found in the taxonomic species S. martorelli. It is assumed that this species is not a natural entity but a species complex. Cytogenetic analysis suggests that continental race I and coastal races II, III and IV have evolved in different ways from a common ancestor called protomartorelli. The coastal races have followed a chromosome-number reduction process, arising from race II by the occurrence of two successive chromosomal fusions. The model of speciation of these coastal forms is based on chromosomal rearrangements, similar to the stasipatric model described by White, although no zones of hybridization have been found in nature.