The forest–tundra ecotone, which spans the whole northern Hemisphere, is the zone where closed forests gradually give way to open arctic or alpine tundra. In northern Norway, the forest–tundra ecotone is formed by three main vegetation types: (1) subarctic forests, where the canopy layer is formed almost exclusively by mountain birch; (2) a transitional zone of tall-shrub tundra dominated by diverse willow species in various combinations; and (3) arctic and alpine tundra, with low vegetation consisting of dwarf shrubs, herbs, grasses, mosses, and lichens.
During the coming decades, the distributions of the different habitat types within the forest–tundra ecotone will change dramatically as a result of the warming climate. Especially open tundra habitats will shrink from their current extent due to shrub expansion. This may lead to significant losses of vertebrate and invertebrate species in open tundra habitats, but also of species living within other components of the forest–tundra ecotone.
Predicting the effects of climate change requires detailed information on current diversity as well as the habitat and niche requirements of individual species. In our project, we use DNA barcodes to identify and to infer niches of insect species in different habitats within the forest–tundra ecotone. The first part of our project concentrates on the most important groups of plant-feeding insects in the north: butterflies and moths, symphytan hymenopterans (sawflies), beetles, leaf-mining flies, and hyperdiverse gall midges. In particular, we aim to barcode larvae collected directly from identified host plants, because the host plants determine the habitat(s) in which a given insect species can survive. In our second main line of investigation, we barcode hymenopteran and dipteran parasitoids reared from the herbivore larvae. Parasitoids are known to be hyperdiverse in subarctic and arctic environments, but are extremely difficult to identify based on morphological traits. Parasitoids constitute the main source of mortality for the larvae of other insects, so understanding parasitoid species richness and community composition in the forest–tundra ecotone will, for example, help to understand the regulation of moth outbreaks in mountain birch forests.
Our barcoding project provides information on insect diversity in different habitats within the northern forest–tundra ecotone, provides genetic tools and reference databases for ongoing and planned environmental monitoring efforts, and results in data that can be used to estimate the threats that specific insect species, taxa, and communities face because of the warming climate of the future.