Studies of mitochondrial DNA, allozyme and morphometric variation in a house mouse hybrid zone

HAUFFE HEIDI; FRAGUEDAKIS-TSOLIS STELLA; MIROL PATRICIA; SEARLE JEREMY

GENETICAL RESEARCH

CAMBRIDGE UNIV PRESS

Año: 2002 vol. 80 p. 117 - 129

0016-6723

An unusual chromosomal hybrid zone of the house mouse, Mus musculus domesticus, exists inUpper Valtellina, Northern Italy, consisting of four Robertsonian (Rb) races and the standard (allacrocentric,or 2n¯40) race, all hybridizing freely within 10 km#. The hybrid zone in Valtellinaprovides an excellent opportunity to study the role of Rb fusions in reproductive isolation andspeciation. This hybrid zone has already been well studied for the distribution of Rb fusions andthe fertility of hybrids, but in order to understand the dynamics of the zone, a basic understandingof the origin and genetic similarity of the chromosomal races is necessary. This paper presents theresults of three different methods of measuring genetic differentiation: multivariate analysis ofmorphological traits and analyses of allozyme variation and mitochondrial DNA sequences. Thestandard race is clearly distinguishable from the three Rb races by all three methods, but the Rbraces are not distinguishable from one another. This provides strong evidence for our previoussuggestions that the well-established Rb races in Valtellina are closely related, and that thestandard race was introduced into the valley more recently from a distant source. The fact that theRb races are indistinguishable is also consistent with our hypothesis that a within-village speciationevent involving two of the races (Hauffe & Searle, 1992) was a recent occurrence. The low level ofallozyme heterozygosity among the Rb races suggests that these populations are the products of atleast one bottleneck. The present article substantially extends earlier studies and provides the ®rstdetailed morphological and molecular analysis of this complex hybrid zone.