Spatio-temporal variation in the structure of a chromosomal polymorphism zone in the house mouse

Abstract

Several long-term temporal analyses of the structure of Robertsonian (Rb) hybrid zones in the western house mouse, Mus musculus domesticus, have been performed. Nevertheless, the detection of gradual or very rapid variations in a zone may be overlooked when the time elapsed between periods of study is too long. The Barcelona chromosomal polymorphism zone of the house mouse covers about 5000 km 2 around the city of Barcelona and is surrounded by 40 chromosome telocentric populations. Seven different metacentrics and mice with diploid numbers between 27 and 40 chromosomes and several fusions in heterozygous state (from one to seven) have been reported. We compare the present (period 2008-2010) and past (period 1996-2000) structure of this zone before examining its dynamics in more detail. Results indicate that there is not a Rb race in this area, which is consistent with the proposal that this zone was probably originated in situ, under a primary intergradation scenario. The lack of individuals with more than five metacentrics in heterozygous state in the current period suggests that selection acted against such mice. By contrast, this situation did not occur for mice with fewer than five fusions in heterozygous condition. Changes in human activity may affect the dynamics of gene flow between subpopulations, thus altering the chromosomal composition of certain sites. Although these local variations may have modified the clinal trend for certain metacentrics, the general staggered structure of the zone has not varied significantly in a decade.

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

“…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 this system, the frequency of metacentrics is distributed in a staggered way over 5,000 km 2 , leading to a progressive reduction in diploid number towards the center of the zone [20].…”

“…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.…”

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

“…Among them, the Barcelona Rb system is found in the provinces of Barcelona, Tarragona and Lleida (Spain), extending over approximately 5000 km 2 (figure 1a). Diploid numbers (2n) range from 27 to 39 chromosomes, with the lowest 2n values observed at sites located approximately 30 km west of the city of Barcelona ( [26] and references therein). This Rb system is characterized by a high level of chromosomal polymorphism, with seven different Rb chromosomes (Rb (3.8), (4.14), (5.15), (6.10), (7.17), (9.11) and (12.13)) showing non-geographically coincident (staggered) clines ( [26] and references therein).…”

“…Diploid numbers (2n) range from 27 to 39 chromosomes, with the lowest 2n values observed at sites located approximately 30 km west of the city of Barcelona ( [26] and references therein). This Rb system is characterized by a high level of chromosomal polymorphism, with seven different Rb chromosomes (Rb (3.8), (4.14), (5.15), (6.10), (7.17), (9.11) and (12.13)) showing non-geographically coincident (staggered) clines ( [26] and references therein). 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).…”