The mammalian model for population studies of B chromosomes: the wood mouse <i>(Apodemus)</i>

Abstract

The presence of B chromosomes was reported in six species of the genus Apodemus (A. peninsulae, A. agrarius, A. sylvaticus, A. flavicollis, A. mystacinus, A. argenteus). High frequencies of Bs were recorded particularly in A. peninsulae and A. flavicollis. The origin of Bs in Apodemus seems to be rather ancient, and it is possible that the supernumerary elements, and/or a tendency for their appearance, were inherited from the common ancestor of the extant species. We have not found any correlated changes between frequencies of Bs and the level of protein polymorphism and/or heterozygosity assessed in electrophoretic studies. No measurable effect of Bs on overall genetic variability was thus revealed in studied populations. The pattern of evolutionary dynamics of Bs can be distinctly different between geographical populations, and both the parasitic and the heterotic models can be applied to explain the maintenance of Bs in different populations. Further studies are desirable to improve our understanding of the complicated evolutionary dynamics of Bs in the Apodemus species. An essential condition for success in this respect is much more detailed information on inheritance and the molecular structure of Bs.

The origin of B chromosomes in yellow-necked mice (Apodemus flavicollis)—Break rules but keep playing the game

“…In this species, Bs were found in almost all studied populations [36–39]. The standard karyotype (2n = 48) can harbour additionally up to eight B chromosomes [40]. The additional elements were described as acrocentric, the same size as the smallest autosome pairs or rarely, even smaller micro-Bs [41, 42].…”

A complex B chromosome system in the Korean field mouse, <i>Apodemus peninsulae</i>

“…Each subspecies occupies its own geographical region and has a slight differentiation in morphometric character (Vorontsov et al, 1977;Koh and Lee, 1994), the transferrin gene (Pavlenko, 1989), and mitochondrial DNA (Serizawa et al, 2002). A. peninsulae belongs to the genus Apodemus, in which six species have been shown to carry B chromosomes (Kartavtseva, 2002;Wó jcik et al, 2004). However, the Korean field mouse shows the widest spectrum of B chromosome variability and about 100 % of animals with Bs are found in most populations.…”

Selection in a Cycling Population: Differential Response Among Skeletal Traits

“…Juveniles were excluded from the spring samples using age estimates from teeth eruption and wear (Adamczewska-Andrzejewska 1967). The Białowieża population of A. flavicollis has been studied for variation in reproductive rates (Adamczewska 1961), daily activity rhythms (Wó jcik and Wołk 1985), body size and haematology (Wołk and Kozłowski 1989), population dynamics (Pucek et al 1993), protein polymorphism (Wó jcik 1993), and B chromosomes (Wó jcik et al 2004). Both juvenile and extremely old individuals were excluded from the morphometric analyses to avoid the effects of ontogenetic changes on our results.…”