Spatial and Temporal Dynamics of Contact Zones Between Chromosomal Races of House Mice, Mus musculus domesticus, on Madeira Island.

Joaquim T Tapisso,Maria Da Graça Ramalhinho,Maria Da Luz Mathias,Sofia I Gabriel,Guila Ganem,Jeremy B Searle,Ana Mota Cerveira,Janice Britton-Davidian

doi:10.3390/genes11070748

Abstract

Analysis of contact zones between parapatric chromosomal races can help our understanding of chromosomal divergence and its influence on the speciation process. Monitoring the position and any movement of contact zones can allow particular insights. This study investigates the present (2012–2014) and past (1998–2002) distribution of two parapatric house mouse chromosomal races—PEDC (Estreito da Calheta) and PADC (Achadas da Cruz)—on Madeira Island, aiming to identify changes in the location and width of their contact. We also extended the 1998–2002 sampling area into the range of another chromosomal race—PLDB (Lugar de Baixo). Clinal analysis indicates no major geographic alterations in the distribution and chromosomal characteristics of the PEDC and PADC races but exhibited a significant shift in position of the Rb (7.15) fusion, resulting in the narrowing of the contact zone over a 10+ year period. We discuss how this long-lasting contact zone highlights the role of landscape on mouse movements, in turn influencing the chromosomal characteristics of populations. The expansion of the sampling area revealed new chromosomal features in the north and a new contact zone in the southern range involving the PEDC and PLDB races. We discuss how different interacting mechanisms (landscape resistance, behaviour, chromosomal incompatibilities, meiotic drive) may help to explain the pattern of chromosomal variation at these contacts between chromosomal races.

Highlights

Since the first study by Gropp et al [1], numerous chromosomal races of the western house mouse (Mus musculus domesticus), resulting from centric or Robertsonian (Rb) fusions of pairs of acrocentric chromosomes, have been identified in Europe and North Africa [2,3]
We extend the sampling area northwards to investigate the northern contact between the PEDC and PADC races
We aimed to investigate: a) the structure of the contact zone between the PEDC and PADC races, by comparing the results from two surveys conducted over ten years apart, b) the chromosomal features of the northern populations of mice, that could not be analysed in the 1998–2002 survey because of unsuccessful trapping, and c) the effect of both environmental and physical barriers on mouse dispersal and the influence they may have on the chromosomal characteristics of the PEDC-PADC and PEDC-PLDB contact zones

Summary

Introduction

Since the first study by Gropp et al [1], numerous chromosomal races of the western house mouse (Mus musculus domesticus), resulting from centric or Robertsonian (Rb) fusions of pairs of acrocentric chromosomes, have been identified in Europe and North Africa [2,3]. It has been argued that chromosomal rearrangements may promote hybrid unfitness leading to reduced interracial gene flow close to the mutation breakpoint, as well as recombination suppression in the same genomic region. This can result in genetic divergence, leading to ’parapatric speciation’, i.e., the situation where, in a geographical context, two neighbouring forms/races become separate species whilst in contact and hybridising [8,10,11,12]

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