Staggered chromosomal hybrid zones in the house mouse: relevance to reticulate evolution and speciation.
In the house mouse there are numerous chromosomal races distinguished by different combinations of metacentric chromosomes. These may come into contact with each other and with the ancestral all-acrocentric race, and form hybrid zones. The chromosomal clines that make up these hybrid zones may be coincident or separated from each other (staggered). Such staggered hybrid zones are interesting because they may include populations of individuals homozygous for a mix of features of the hybridising races. We review the characteristics of four staggered hybrid zones in the house mouse and discuss whether they are examples of primary or secondary contact and whether they represent reticulate evolution or not. However, the most important aspect of staggered hybrid zones is that the homozygous populations within the zones have the potential to expand their distributions and become new races (a process termed 'zonal raciation'). In this way they can add to the total 'stock' of chromosomal races in the species concerned. Speciation is an infrequent phenomenon that may involve an unusual set of circumstances. Each one of the products of zonal raciation has the potential to become a new species and by having more races increases the chance of a speciation event.
Department of Biology, University of York, PO Box 373, York YO10 5YW, UK. gunduzi@omu.edu.tr.
Islam
I
Gündüz
Department of Biology, University of York, PO Box 373, York YO10 5YW, UK. christianne.pollock@pms.ac.uk.
Christianne L
CL
Pollock
Department of Biology, University of York, PO Box 373, York YO10 5YW, UK. mdg500@york.ac.uk.
Mabel D
MD
Giménez
Department of Biology, University of York, PO Box 373, York YO10 5YW, UK. dwgfoerster@googlemail.com.
Daniel W
DW
Förster
School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK. tawhite201@hotmail.com.
Thomas A
TA
White
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA. sans@email.arizona.edu.
Maria A
MA
Sans-Fuentes
Department of Biology, University of York, PO Box 373, York YO10 5YW, UK. heidi.hauffe@iasma.it.
Heidi C
HC
Hauffe
Departament de Biologia Animal, de Biologia Vegetal i d'Ecologia, Facultat de Biociènces, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain. jacint.ventura.queija@uab.es.
Jacint
J
Ventura
Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain. marialopez@ub.edu.
María José
MJ
López-Fuster
Department of Biology, University of York, PO Box 373, York YO10 5YW, UK. jbs3@york.ac.uk.
Jeremy B
JB
Searle