title: Chromosomal rearrangements, phenotypic variation and modularity: a case study from a contact zone between house mouse Robertsonian races in Central Italy.
abstract: The Western European house mouse, Mus musculus domesticus, is well-known for the high frequency of Robertsonian fusions that have rapidly produced more than 50 karyotipic races, making it an ideal model for studying the mechanisms of chromosomal speciation. The mouse mandible is one of the traits studied most intensively to investigate the effect of Robertsonian fusions on phenotypic variation within and between populations. This complex bone structure has also been widely used to study the level of integration between different morphogenetic units. Here, with the aim of testing the effect of different karyotypic assets on the morphology of the mouse mandible and on its level of modularity, we performed morphometric analyses of mice from a contact area between two highly metacentric races in Central Italy. We found no difference in size, while the mandible shape was found to be different between the two Robertsonian races, even after accounting for the genetic relationships among individuals and geographic proximity. Our results support the existence of two modules that indicate a certain degree of evolutionary independence, but no difference in the strength of modularity between chromosomal races. Moreover, the ascending ramus showed more pronounced interpopulation/race phenotypic differences than the alveolar region, an effect that could be associated to their different polygenic architecture. This study suggests that chromosomal rearrangements play a role in the house mouse phenotypic divergence, and that the two modules of the mouse mandible are differentially affected by environmental factors and genetic makeup.
authors: Department of Biology Lehrstuhl für Zoologie und Evolutionsbiologie University of Konstanz Universitätsstraße 1078457 Konstanz Germany; Dipartimento di Biologia e Biotecnologie "Charles Darwin" Universitá di Roma "La Sapienza" via Borelli 5000161 Roma Italy.
authors: Paolo
authors: P
authors: Franchini
authors: CNR Istituto per lo Studio degli Ecosistemi Verbania Italia.
authors: Paolo
authors: P
authors: Colangelo
authors: Department of Biology Lehrstuhl für Zoologie und Evolutionsbiologie University of Konstanz Universitätsstraße 10 78457 Konstanz Germany.
authors: Axel
authors: A
authors: Meyer
authors: Department of Biology Lehrstuhl für Zoologie und Evolutionsbiologie University of Konstanz Universitätsstraße 1078457 Konstanz Germany; School of Earth Environmental and Biological Sciences Queensland University of Technology Gardens Point 4000 Brisbane Australia.
authors: Carmelo
authors: C
authors: Fruciano
keywords: Chromosomal speciation; Robertsonian fusions; geometric morphometrics; house mouse; modularity; phenotypic variation