If chromosomal rearrangements could become established, they could provide a basis for rapid speciation. A rare rearrangement would be unlikely to be paired with a matching chromosome and would therefore be selected against. However, rearrangements could become common enough to yield a successfully interbreeding population, either by something like molecular drive or by inbreeding in which siblings would be likely to share the rearrangement. Chromosomal differences between species are fairly common, but they also occur within species. The importance of chromosomal changes for speciation remains unknown.
Many hypotheses can account for speciation.
Each hypothesis requires some special conditions. Which hypothesis applies in any particular case is difficult to determine, and which conditions are generally more important remain uncertain.