Molecular insights into the colonization and chromosomal diversification of Madeiran house mice

Abstract

The colonization history of Madeiran house mice was investigated by analysing the complete mitochondrial (mt) D-loop sequences of 156 mice from the island of Madeira and mainland Portugal, extending on previous studies. The numbers of mtDNA haplotypes from Madeira and mainland Portugal were substantially increased (17 and 14 new haplotypes respectively), and phylogenetic analysis confirmed the previously reported link between the Madeiran archipelago and northern Europe. Sequence analysis revealed the presence of four mtDNA lineages in mainland Portugal, of which one was particularly common and widespread (termed the 'Portugal Main Clade'). There was no support for population bottlenecks during the formation of the six Robertsonian chromosome races on the island of Madeira, and D-loop sequence variation was not found to be structured according to karyotype. The colonization time of the Madeiran archipelago by Mus musculus domesticus was approached using two molecular dating methods (mismatch distribution and Bayesian skyline plot). Time estimates based on D-loop sequence variation at mainland sites (including previously published data from France and Turkey) were evaluated in the context of the zooarchaeological record of M. m. domesticus. A range of values for mutation rate (mu) and number of mouse generations per year was considered in these analyses because of the uncertainty surrounding these two parameters. The colonization of Portugal and Madeira by house mice is discussed in the context of the best-supported parameter values. In keeping with recent studies, our results suggest that mutation rate estimates based on interspecific divergence lead to gross overestimates concerning the timing of recent within-species events.

Origin of the chromosomal radiation of Madeiran house mice: a microsatellite analysis of metacentric chromosomes

“…Karyotypes of mice were determined in previous studies, as follows: Madeira and Portugal, Förster et al (2009);Denmark, Smadja et al (2004);Spain, Gündüz et al (2001b); northern Italy, Hauffe and Searle (1993) and Panithanarak et al (2004);and Scotland, Searle (1991), Searle et al (1993) and Palmer (1997).…”

“…It is worth noting that the populations on Madeira characterised by metacentric 3.8 occupy the eastern portion of the island (Figure 1), where the main port and airport are located; this is the area most likely to receive mouse immigrants from Portugal, and mice here show within-race polymorphism involving metacentrics and their acrocentric homologues (Britton-Davidian et al, 2005, 2007. However, it has not been conclusively determined if this chromosomal polymorphism is due to immigration of standard karyotype (all-acrocentric) mice, and no mice with what could be considered Portuguese mtDNA haplotypes have been detected in this area (Gündüz et al, 2001a;Förster et al, 2009).…”

“…This includes metacentric 3.8, which phylogenetic studies suggest is likely to be one of the first Rb fusions to have arisen on the island (BrittonDavidian et al, 2005;White et al, 2010). As the proposed north European source of the Madeiran mice (based on mitochondrial (mt) DNA analysis: Gündüz et al (2001a) and Förster et al (2009)) includes a region of Denmark inhabited by races fixed for metacentric 3.8 (Piálek et al (2005), and references therein), it is possible that this metacentric was introduced to Madeira from Denmark during colonisation. Such (human-mediated) long-distance dispersal of metacentric-bearing mice has already been confirmed for some European populations (Riginos and Nachman, 1999).…”

“…The island is a Portuguese dependency and passive transport (by humans) of mice from mainland Portugal to Madeira is expected to have occurred since the island's settlement in the 15th century. In spite of a virtual absence of Portuguese mtDNA sequences on Madeira (Gündüz et al, 2001a;Förster et al, 2009), there is high genic similarity between most Madeiran metacentric races and Portuguese house mice at nuclear allozyme markers (Britton-Davidian et al, 2007). It has been proposed that mice introduced from Portugal likely represent a secondary wave of colonisers after an initial colonisation from northern Europe (Britton-Davidian et al, 2007;Förster et al, 2009).…”

“…In spite of a virtual absence of Portuguese mtDNA sequences on Madeira (Gündüz et al, 2001a;Förster et al, 2009), there is high genic similarity between most Madeiran metacentric races and Portuguese house mice at nuclear allozyme markers (Britton-Davidian et al, 2007). It has been proposed that mice introduced from Portugal likely represent a secondary wave of colonisers after an initial colonisation from northern Europe (Britton-Davidian et al, 2007;Förster et al, 2009). Several Portuguese mouse populations that could have contributed to this second wave of colonisers were included in the study (that is, from cities along the Atlantic coast with active harbours since the settlement period of Madeira from Portugal).…”