Clinal analysis of a chromosomal hybrid zone in the house mouse

Abstract

These studies centre on the 'Barcelona' karyotypic race of the western house mouse (Mus musculus domesticus), first described by Adolph & Klein (1981). This is one of many races within M. m. domesticus characterized by metacentric chromosomes that have originated by repeated Robertsonian fusions, with perhaps further modification by whole-arm reciprocal translocations. Data on 111 mice from 20 sites show that the race is centred 24 km to the west of Barcelona city and has a homozygous metacentric karyotype of 2n = 28 (3.8, 4.14, 5.15, 6.10, 9.11, 12.13). The race has a small range, and mice with the standard 40-acrocentric karyotype were caught only 30 km from the race centre. Throughout the area of occurrence of metacentrics there is polymorphism (i.e. presence of acrocentrics in the population), although all six metacentrics approach fixation close to the race centre. Thus, there is a hybrid zone between the Barcelona and standard races. The centres and widths of all clines (except 3.8) were determined. Likelihood ratio tests showed that most of the cline centres differed significantly in position (i.e. the clines were staggered) and the clines for metacentrics 6.10 and 9.11 were significantly narrower than those for 4.14, 5.15 and 12.13. Overall, the clines tended to be wider the further they were from the race centre. There are various possible explanations for this hybrid zone structure and further data are needed to distinguish between them.

Chromosomal and allozyme analysis of a hybrid zone between parapatric Robertsonian races of the house mouse: a case of monobrachial homology

“…Thus, within each system, two types of contact zones may exist, those between Rb and all-acrocentric mice and those between different Rb races. The consequences of hybrid unfitness on the structure and width of the hybrid zones will vary according to the nature of the chromosomal differences between the groups in contact (Gropp et al, 1982b;Barton and Hewitt, 1983;Capanna et al, 1985;Bauchau et al, 1990;Hauffe and Searle, 1993;Searle, 1993;Searle et al, 1993;Castiglia and Capanna, 1999a;Gündüz et al, 2001). In contact zones between Rb and all-acrocentric populations, hybrids will carry trivalents at meiosis, formed by pairing between the Rb fusions and the homologous acrocentric chromosomes.…”

Genetic recombination variation in wild Robertsonian mice: on the role of chromosomal fusions andPrdm9allelic background

“…Owing to the absence of a Rb race, as defined by Hausser et al [27], this system has been considered to be a Rb polymorphism zone rather than be a typical hybrid zone ( [26] and references therein). Although the chromosomal composition and structure of the Barcelona Rb system are known [26,28], the meiotic dynamics and genetic recombination of the mice that comprise it remain elusive. Here, we have studied the recombination features of this Rb system with two specific aims: (i) to analyse the effect of Rb fusions on both recombination rate and its chromosomal distribution, and (ii) to determine the genetic and mechanistic factors that are shaping the process.…”

Effect of chromosomal reorganizations on morphological covariation of the mouse mandible: insights from a Robertsonian system of Mus musculus domesticus

“…Jointly, these sets of populations are called Rb systems [5]. One of these, named 'Barcelona' Rb system, is present on the Northeastern Iberian Peninsula, specifically in part of the provinces of Barcelona, Tarragona and Lleida [17][18][19][20]. The set of metacentrics that characterizes this Rb system consists of Rb(3.8), Rb(4.14), Rb(5.15), Rb(6.10), Rb(7.17), Rb(9.11) and Rb (12.13), where the pairs of numbers refer to the acrocentric autosomes that gave rise to the metacentric in question.…”

“…In order to know the relative importance of direct interactions and parallel variation of developmental pathways in generating morphological covariation in the mouse mandible, we studied symmetric and asymmetric shape changes separately, which are usually termed symmetric component and asymmetric component of shape variation respectively. Lastly, because chromosomal variation in the 'Barcelona' Rb system is geographically arranged [18,20], we also assessed the effect of geographic distance on the covariance structure of the mandible.…”