Comparative study of the phylogenetic structure in six Apodemus species (Mammalia, Rodentia) inferred from ISSR-PCR data

The utility of the Inter Simple Sequence Repeat-Polymerase Chain Reaction (ISSR-PCR) was explored in order to determine genetic variation in six species of the genus Apodemus (A. flavicollis, A. sylvaticus, A. uralensis, A. agrarius, A. mystacinus and A. epimelas) at the individual level, population level, in separate geographic samples and in the species as a whole. Six optimized primers produced highly reproducible and polymorphic DNA markers with 98.3% polymorphic bands on a total sample of 91 individuals from 32 localities in Europe and Asia. Moreover, each primer allowed for an exact diagnosis of each of the six Apodemus species and thus provides a simple and reliable tool for the hitherto problematic discrimination of species from the subgenus Sylvaemus. Genetic distances between species ranged from 0.079, among the closely related A. flavicollis and A. sylvaticus, to 0.203 between A. mystacinus and A. agrarius. A. flavicollis, A. uralensis and A. sylvaticus display a strong population substructure. The range of genetic distances among geographic samples within last two species reaches the values obtained for closely related species. ISSR markers proved to be a simple and reliable tool for species diagnosis, as well as for estimating genetic diversity below the species level and for closely related species, but they showed questionable reliability for larger genetic distances.Ministry of Science and Technological Development of the Republic of Serbia [173003

Comparative study of the phylogenetic structure in six Apodemus species (Mammalia, Rodentia) inferred from ISSR-PCR data

The utility of the Inter Simple Sequence Repeat-Polymerase Chain Reaction (ISSR-PCR) was explored in order to determine genetic variation in six species of the genus Apodemus (A. flavicollis, A. sylvaticus, A. uralensis, A. agrarius, A. mystacinus and A. epimelas) at the individual level, population level, in separate geographic samples and in the species as a whole. Six optimized primers produced highly reproducible and polymorphic DNA markers with 98.3% polymorphic bands on a total sample of 91 individuals from 32 localities in Europe and Asia. Moreover, each primer allowed for an exact diagnosis of each of the six Apodemus species and thus provides a simple and reliable tool for the hitherto problematic discrimination of species from the subgenus Sylvaemus. Genetic distances between species ranged from 0.079, among the closely related A. flavicollis and A. sylvaticus, to 0.203 between A. mystacinus and A. agrarius. A. flavicollis, A. uralensis and A. sylvaticus display a strong population substructure. The range of genetic distances among geographic samples within last two species reaches the values obtained for closely related species. ISSR markers proved to be a simple and reliable tool for species diagnosis, as well as for estimating genetic diversity below the species level and for closely related species, but they showed questionable reliability for larger genetic distances.Ministry of Science and Technological Development of the Republic of Serbia [173003

Characterization of the satellite DNA Msat-160 from species of Terricola (Microtus) and Arvicola (Rodentia, Arvicolinae)

In the subfamily Arvicolinae (Cricetidae, Rodentia) the satellite DNA Msat-160 has been so far described in only some species from the genus Microtus and in one species from another genus, Chionomys nivalis. Here we cloned and characterized this satellite in two new arvicoline species, Microtus (Terricola) savii and Arvicola amphibius (terrestris). We have also demonstrated, by PCR and FISH, its existence in the genomes of several other species from both genera. These results suggest that Msat-160 already occurred in the common ancestor of the four genera/subgenera of Arvicolinae (Microtus, Chionomys, Arvicola, and Terricola). In Arvicola and Terricola, Msat-160 showed the basic monomer length of 160 bp, although a higher-order repeat (HORs) of 640 bp could have been probably replacing the original monomeric unit in A. a. terrestris. Msat-160 was localized by FISH mostly on the pericentromeric regions of the chromosomes, but the signal intensity and the number of carrier chromosomes varied extremely even between closely related species, resulting in a species-specific pattern of chromosomal distribution of this satellite. Such a variable pattern most likely is a consequence of a rapid amplification and contraction of particular repeats in the pericentromeric regions of chromosomes. In addition, we proposed that the rapid variation of pericentromeric repeats is strictly related to the prolific species radiation and diversification of karyotypes that characterize Arvicolinae lineage. Finally, we performed phylogenetic analysis in this group of related species based on Msat-160 that results to be in agreement with previously reported phylogenies, derived from other molecular markers

R2d2 drives selfish sweeps in the house mouse

A selective sweep is the result of strong positive selection driving newly occurring or standing genetic variants to fixation, and can dramatically alter the pattern and distribution of allelic diversity in a population. Population-level sequencing data have enabled discoveries of selective sweeps associated with genes involved in recent adaptations in many species. In contrast, much debate but little evidence addresses whether "selfish" genes are capable of fixation - thereby leaving signatures identical to classical selective sweeps - despite being neutral or deleterious to organismal fitness. We previously described R2d2, a large copy-number variant that causes nonrandom segregation of mouse Chromosome 2 in females due to meiotic drive. Here we show population-genetic data consistent with a selfish sweep driven by alleles of R2d2 with high copy number (R2d2) in natural populations. We replicate this finding in multiple closed breeding populations from six outbred backgrounds segregating for R2d2 alleles. We find that R2d2 rapidly increases in frequency, and in most cases becomes fixed in significantly fewer generations than can be explained by genetic drift. R2d2 is also associated with significantly reduced litter sizes in heterozygous mothers, making it a true selfish allele. Our data provide direct evidence of populations actively undergoing selfish sweeps, and demonstrate that meiotic drive can rapidly alter the genomic landscape in favor of mutations with neutral or even negative effects on overall Darwinian fitness. Further study will reveal the incidence of selfish sweeps, and will elucidate the relative contributions of selfish genes, adaptation and genetic drift to evolution