During the last 15 years the internal transcribed spacer (ITS) of nuclear DNA has been used as a target for analyzing fungal diversity in environmental samples, and has recently been selected as the standard marker for fungal DNA barcoding. In this study we explored the potential amplification biases that various commonly utilized ITS primers might introduce during amplification of different parts of the ITS region in samples containing mixed templates ('environmental barcoding'). We performed in silico PCR analyses with commonly used primer combinations using various ITS datasets obtained from public databases as templates.

In order to understand the role of herbivores in trophic webs, it is essential to know what they feed on. Diet analysis is, however, a challenge in many small herbivores with a secretive life style. In this paper, we compare novel (high-throughput pyrosequencing) DNA barcoding technology for plant mixture with traditional microhistological method. We analysed stomach contents of two ecologically important subarctic vole species, Microtus oeconomus and Myodes rufocanus, with the two methods. DNA barcoding was conducted using the P6-loop of the chloroplast trnL (UAA) intron.

Traditionally, the Arctic has been viewed as an ‘evolutionary freezer’ with low evolutionary rates caused by extreme environmental constraints and depauperated by repeated glaciations. This view has been modified in recent years. Here we summarise recent studies demonstrating a very high diversity relative to the age of the arctic ecosystem (2–3 million years). Arctic species' diversity is underestimated in the sense that most arctic plants are polyploids, combining the genomes of several ancestral species and that they may contain considerable hidden diversity as cryptic species. There are now many examples of arctic species that originated in the Pleistocene, via divergent evolution or successively higher-level polyploidizations, following hybridization. Apart from genetic diversity associated with polyploid origin, many arctic plants show considerable variation both within and among populations. Genetic diversity varies with breeding system, frequency of inter- and intraspecific hybridization, and history in terms of refugial isolation and range shifts. Many cold-adapted species probably proliferated in vast tundra populations during most of the Pleistocene, followed by broad-fronted postglacial recolonisation resulting in little loss of genetic diversity. Migration at the beginning and end of warm and cold periods is likely to be an important driver of diversification. Molecular data have now provided ample evidence for extreme long-distant colonisation ability of many arctic plants. Local variants may thus spread over vast distances and create multiple hotspots for evolutionary novelty, and it is possible that even small differences in immigration history may have a considerable effect on the evolutionary emergence of diversity.

Polyploidy, the duplication of entire genomes, plays a major role in plant evolution. In allopolyploids, genome duplication is associated with hybridization between two or more divergent genomes. Successive hybridization and polyploidization events can build up species complexes of allopolyploids with complicated network-like histories, and the evolutionary history of many plant groups cannot be adequately represented by phylogenetic trees because of such reticulate events. The history of complex genome mergings within a high-polyploid species complex in the genus Cerastium (Caryophyllaceae) is here untangled by the use of a network algorithm and noncoding sequences of a low-copy number gene. The resulting network illustrates how hybridization and polyploidization have acted as key evolutionary processes in creating a plant group where high-level allopolyploids clearly outnumber extant parental genomes.