Colonization history of north European field voles (Microtus agrestis) revealed by mitochondrial DNA

The genetic structure of field vole (Microtus agrestis) populations from northern Europe was examined by restriction fragment length polymorphisms of mitochondrial DNA (mtDNA) in 150 individuals from 67 localities. A total of 83 haplotypes was observed, most of which were rare and highly localized geographically. Overall nucleotide diversity was high (134%), but showed a tendency to decrease with higher latitude. Two major mtDNA lineages differing by 2% in nucleotide sequence were identified. A southern mtDNA lineage was observed in field voles from Britain, Denmark and southern and central Sweden, whereas voles from Finland and northern Sweden belonged to a northern lineage. The strict phylogeographic pattern suggests that the present population generic structure in field voles reflects glacial history: the two groups are derived from different glacial refugia, and recolonized Fennoscandia from two directions. A 150–200-km-wide secondary contact zone between the two mtDNA groups was found in northern Sweden. Distinct phylogeographic substructuring was observed within both major mtDNA groups.     

Secondary metabolite from Nostoc XPORK14A inhibits photosynthesis and growth of Synechocystis PCC 6803

Screening of 55 different cyanobacterial strains revealed that an extract from Nostoc XPORK14A drastically modifies the amplitude and kinetics of chlorophyll a fluorescence induction of Synechocystis PCC 6803 cells. After 2 d exposure to the Nostoc XPORK14A extract, Synechocystis PCC 6803 cells displayed reduced net photosynthetic activity and significantly modified electron transport properties of photosystem II under both light and dark conditions. However, the maximum oxidizable amount of P700 was not strongly affected. The extract also induced strong oxidative stress in Synechocystis PCC 6803 cells in both light and darkness. We identified the secondary metabolite of Nostoc XPORK14A causing these pronounced effects on Synechocystis cells. Mass spectrometry and nuclear magnetic resonance analyses revealed that this compound, designated as M22, has a non‐peptide structure. We propose that M22 possesses a dual‐action mechanism: firstly, by photogeneration of reactive oxygen species in the presence of light, which in turn affects the photosynthetic machinery of Synechocystis PCC 6803; and secondly, by altering the in vivo redox status of cells, possibly through inhibition of protein kinases.     

Colonization history in Fennoscandian rodents

Fennoscandia probably constitutes one of the best places on earth to study faunal history. During the height of the most recent glacial period Fennoscandia was completely covered with ice. Thus, the majority of extant species must originate from ancestors who survived the latest glaciation in non-glaciated areas outside Fennoscandia. Moreover, the geography and geological history of Fennoscandia suggests that post-glacial recolonization by land mammals must have been restricted to specific routes in time and space. Phylogeographic surveys of mitochondrial DNA (mtDNA) variation in Fennoscandian rodents have demonstrated that glacial history and patterns of post-glacial colonization have played a major role in shaping present day patterns of genetic differentiation within species. Thus, the genetic imprints of historical demographic conditions and vicariant geographic events have been retained within species and can be used to infer the history of populations. The field vole (Microtus agrestis) is used to illustrate these data and processes. Comparisons are made with phylogeographic surveys of the bank vole (Clethrionomys glareolus) , the eastern house mouse (Mus musculus) and the wood lemming (Myopus schisticolor) as well as a few other species for which less extensive studies have been performed. The main patterns of post-glacial colonization of Fennoscandia by rodents are described. The effects of timing and patterns of colonization on contemporary population genetic structure and levels of genetic variation are discussed. Specifically, the effects of hybridization and introgression as well as founder events and bottlenecks are explored.     

Isolation and characterization of polymorphic microsatellite loci in the field vole,Microtus agrestis,and their cross‐utility in the common vole,Microtus arvalis

We developed nine polymorphic microsatellite loci for the field vole, Microtus agrestis. The number of alleles ranged from five to 15 and observed heterozygosities ranged from 0.40 to 1.00. We also tested the microsatellite loci for amplification and polymorphism in the congeneric species Microtus arvalis. Five of the nine loci were successfully analysed in this species. The microsatellite markers will be employed in studies of reproductive success and fine‐scale spatial genetic structure.     

Low mitochondrial DNA variation and recent colonization of Scandinavia by the wood lemming Myopus schisticolor

The population genetic structure of wood lemmings ( Myopus schisticolor ) from Scandinavia, Finland and western Siberia was examined by restriction fragment length polymorphism of mitochondrial DNA (mtDNA) in 45 individuals from six localities. The 12 observed mtDNA haplotypes demonstrated a distinct phylogeographic pattern, suggesting that the postglacial colonization of Scandinavia by wood lemmings occurred from north-east. However, a very low level of haplotype and nucleotide diversity and a lack of geographical structure were found within Scandinavia. The limited mtDNA diversity in the Scandinavian populations probably reflects recent divergence in situ after colonization by a limited number of founders. Allozyme data support this scenario.