摘要
Chromosomal evolution is widely considered an important driver of speciation because it can promote the establishment of reproductive barriers.Karyotypic reorganization is also expected to affect the mea n phe no type,as well as its developme nt and patter ns of phenotypic in tegrati on,through processes such as variation in genetic linkage between quantitative trait loci or between regulatory regions and their targets.Here we explore the relationship between chromosomal evolution and phenotypic integration by analyzing a well-known house mouse parapatric contact zone between a highly derived Robertsonian(Rb)race(2n=22)and populations with standard karyotype(2n=40).Populations with hybrid karyotypes are scattered throughout the hybrid zone connecting the two parental races.Using mandible shape data and geometric morphometries,we test the hypothesis that patter ns of in tegration progressively diverge from the"normal"integration pattern observed in the standard race as they accumulate Rb fusions.We find that the main pattern of integration observed between the posterior and anterior part of the mandible can be largely attributed to allometry.We find no support for a gradual increase in divergence from normal patterns of integration as fusions accumulate.Surprisingly,however,we find that the derived Rb race(2n=22)has a distinct allometric trajectory compared with the standard race.Our results suggest that either individual fusions disproportionately affect patterns of integration or that there are mechanisms which"purge"extreme variants in hybrids(e.g.reduced fitness of hybrid shape).
基金
the Ministry of Scientific Research and Education,Italy(MIUR).
