ALBERT

Beschreibung: Sequence variation in the mtDNA control region of Arctic charr Salvelinus alpinus and Dolly Varden Salvelinus malma from 56 Siberian and North American populations was analysed to assess their phylogeographic relationships and the origins of sympatric forms. Phylogenetic trees confirm the integrity of phylogroups reported in previous mtDNA studies except that the Siberian group does not separate as a single cluster. Haplotype network analysis indicates the proximity of Siberian and Atlantic haplotypes. These are considered as one Eurasian group represented by the Atlantic, east Siberian (interior Siberia including Transbaikalia, Taimyr) and Eurosiberian (Finland, Spitsbergen, Taimyr) sub-groups. Salvelinus alpinus with presumably introgressed Bering group (malma) haplotypes were found along eastern Siberian coasts up to the Olenek Bay and the Lena Delta region, where they overlap with the Eurasian group and in the easternmost interior region. It is proposed that Siberia was colonized by S. alpinus in two stages: from the west by the Eurasian group and later from the east by the Bering group. The high diversity of Eurasian group haplotypes in Siberia indicates its earlier colonization by S. alpinus as compared with the European Alps. This colonization was rapid, proceeded from a diverse gene pool, and was followed by differential survival of ancestral mtDNA lineages in different basins and regions, and local mutational events in isolated populations. The results presented here support a northern origin of Transbaikalian S. alpinus, the dispersion of S. alpinus to the Lake Baikal Basin from the Lena Basin, segregation of S. alpinus between Lena tributaries and their restricted migration over the divides between sub-basins. These results also support sympatric origin of intralacustrine forms of S. alpinus.

Beschreibung: Recent Pan-Arctic shrub expansion has been interpreted as a response to a warmer climate. However, herbivores can also influence the abundance of shrubs in arctic ecosystems. We addressed these alternative explanations by following the changes in plant community composition during the last 10 years in permanent plots inside and outside exclosures with different mesh sizes that exclude either only reindeer or all mammalian herbivores including voles and lemmings. The exclosures were replicated at three forest and tundra sites at four different locations along a climatic gradient (oceanic to continental) in northern Fennoscandia. Since the last 10 years have been exceptionally warm, we could study how warming has influenced the vegetation in different grazing treatments. Our results show that the abundance of the dominant shrub, Betula nana, has increased during the last decade, but that the increase was more pronounced when herbivores were excluded. Reindeer have the largest effect on shrubs in tundra, while voles and lemmings have a larger effect in the forest. The positive relationship between annual mean temperature and shrub growth in the absence of herbivores and the lack of relationships in grazed controls is another indication that shrub abundance is controlled by an interaction between herbivores and climate. In addition to their effects on taller shrubs (〉 0.3 m), reindeer reduced the abundance of lichens, whereas microtine rodents reduced the abundance of dwarf shrubs (〈 0.3 m) and mosses. In contrast to short-term responses, competitive interactions between dwarf shrubs and lichens were evident in the long term. These results show that herbivores have to be considered in order to understand how a changing climate will influence tundra ecosystems.

Beschreibung: Snowfall rates at the Princess Elisabeth station, East Antarctica (71°57'S - 23°21'E) in 2011. The snowfall rate is in mm/hour (w.e) dervied from the ZE-SR relation. - FOR DETAILS AND DATA AVAILABILITY, SEE : https://ees.kuleuven.be/hydrant/aerocloud/

Beschreibung: Snowfall rates at the Princess Elisabeth station, East Antarctica (71°57'S - 23°21'E) in 2012. The snowfall rate is in mm/hour (w.e) dervied from the ZE-SR relation. - FOR DETAILS AND DATA AVAILABILITY, SEE : https://ees.kuleuven.be/hydrant/aerocloud/

Beschreibung: Snowfall rates at the Princess Elisabeth station, East Antarctica (71°57'S - 23°21'E) in 2013. The snowfall rate is in mm/hour (w.e) dervied from the ZE-SR relation. - FOR DETAILS AND DATA AVAILABILITY, SEE : https://ees.kuleuven.be/hydrant/aerocloud/

Beschreibung: Snowfall rates at the Princess Elisabeth station, East Antarctica (71°57'S - 23°21'E) in 2014. The snowfall rate is in mm/hour (w.e) dervied from the ZE-SR relation. - FOR DETAILS AND DATA AVAILABILITY, SEE : https://ees.kuleuven.be/hydrant/aerocloud/