We studied reciprocal hybrids of Mus musculus musculus and M. m. domesticus. These two subspecies of house mouse were found to differ in their social behaviour, the former being less aggressive than the latter. The paternal effect on aggression (observed repeatedly in laboratory mice) was not found. However, F2 generation mice were less aggressive than those from the F1 generation, and the maternal effect was also significant in a homogenous test set.
The common shrew is a major evolutionary model for understanding the factors that lead to chromosomal subdivision; it is one of the most chromosomally variable species. We karyotyped 106 common shrews (Sorex araneus) from 24 localities in north-eastern European Russia which we showed to belong to five chromosomal races: Kirillov, Manturovo, Petchora, Serov and Sok. These new data were combined with published results on 146 individuals from 55 localities (with three additional races: Kanin, Yagry and Yuryuzan) to provide a substantive analysis of chromosomal variation in this region. The ranges of the eight races were mapped, the areas of contacts between neighbouring races were determined and new interracial hybrid zones were localised. In total, F
1 hybrid karyotypes were found in 22 individuals from 11 localities; including our demonstration of Manturovo-Petchora, Manturovo-Sok, Petchora-Serov, Petchora-Sok and Serov-Sok F 1 hybrid karyotypes for the first time. These hybrids would be expected to produce ring-of-four, ring-of-six or ring-
of-eight meiotic configurations. The distribution of the races could not readily be related to environmental or geographic features, and in particular major rivers did not appear important in separation of races. This represents one of the most detailed studies of chromosomal variation in the common shrews at a regional geographic scale and is of especial significance because north-eastern European Russia has been little affected by human activity, and therefore the results are likely to represent fully natural processes.
Crested newts (Triturus cristatus superspecies) are a group of closely related species with parapatric distributions that are likely to interbreed where their ranges meet. Coexistence of three species of the complex (Triturus cristatus, T. dobrogicus and T. carnifex) has been recently confirmed in central Europe. In this study we aim to elucidate the distribution of crested newts in contact zones in the Czech Republic and Slovakia, and determine the extent of hybridization and introgression using nuclear (microsatellites and Randomly Amplified Polymorphic DNA, RAPD) and mitochondrial DNA (mtDNA) markers. Nuclear markers reveal hybrid zones between T. cristatus and T. dobrogicus at the foothills of the Carpathians in southern Slovakia, and between T. cristatus and T. carnifex in the southern parts of the Czech Republic. Analysis of mitochondrial cytochrome b sequences reveals T. cristatus and T. dobrogicus-specific haplotypes in contact zones in southern Slovakia. Surprisingly, most T. carnifex and individuals with mixed ancestry between T. carnifex and T. cristatus possess haplotypes specific for T. dobrogicus, most likely as a result of historical mtDNA introgression. Only one T. carnifex-specific haplotype carried by a single specimen is found in the Czech Republic. Our study shows that genetic structure of central European populations of crested newts is complex and influenced by historical and contemporary hybridization.
Analysis of the hybridisation events between two Iberian Chondrostoma species in the Távora River (Douro Basin) suggests different levels of trait introgression. Nuclear traits studied showed different introgression levels, whereas mitochondrial DNA introgression was not found. Lack of mtDNA introgression suggests that male and female hybrids may not equally fit or that possibly backcross matings may not be random. This could be contributing to the maintenance of a relative morphologic cohesion of hybridizing species, in spite of differences relative to allopatric populations. The hybrid zone was possibly originated by secondary contacts between populations of the species involved, motivated by connectivity between adjacent basins. Reanalysis of the hybridizing taxa revealed that Chondrostoma macrolepidotum is the species involved in the interspecific crosses with C. duriense, instead of C. arcasii as previously proposed.
Overlapping measurements in the length of the genitalia of Leptidea sinapis/reali collected in Slovenia triggered an investigation of a possible natural hybridization between these two well known sibling species of butterflies. Random polymorphic DNA (RAPD) was used to generate species specific markers and sequences of the cytochrome oxidase subunit one gene for determination of the progeny. RAPD's clustering and mitochondrial DNA (mtDNA) phylogeny were congruent with the taxonomic placement of specimens of both species, but slightly incongruent with the results of the analysis of genital morphology. Two specimens with L. reali genitalia measurements, but genetically belonging to L. sinapis, had species specific RAPD markers of both species indicating probable hybrid origin. All the specimens with genitalia of intermediate length were also genetically assigned to L. sinapis indicating a possible one way introgression as predicted from their genitalia morphology. Leptidea sinapis was found predominantly in xerothermic habitats in Slovenia, whereas L. reali was more of a generalist except in the sub-Mediterranean region where it is limited to humid meadows.