Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food-web stability. In lakes, littoral and pelagic food-web compartments are typically coupled and controlled by generalist fish top predators. However, the ...

Understanding how a monophyletic lineage of a species diverges into several adaptive forms has received increased attention in recent years, but the underlying mechanisms in this process are still under debate. Postglacial fishes are excellent model organisms for exploring this process, especially the initial stages of ecological speciation, as postglacial lakes represent replicated discrete ...

Natural populations often vary in their degree of ecological, morphological and genetic divergence. This variation can be arranged along an ecological speciation continuum of increasingly discrete variation, with high inter-individual variation at one end and well defined species in the other. In postglacial fishes, evolutionary divergence has commonly resulted in the co-occurrence of a pelagic and ...

Invasions of non-native species represent a global problem of great scientific interest. Here we study in detail the response in population and life history characteristics of closely related native species, with divergent habitat preferences, that are impacted by an invading species over a sufficient time period to allow a new stable state to become established. A time series of 20 years starting ...

The numbers of divers, ducks, gulls, terns and waders in the 15 km2 oligotrophic lake Takvatn, North Norway, were estimated six times during 1983-2012. Systematic mapping surveys were done by boat within the first week after the ice-break in June. Twenty-one species were observed over the years and 12 were regarded as breeding on the lake. Red-breasted merganser Mergus serrator was the dominant diving ...

In adaptive radiations, ecological opportunity (i.e. niche availability) is considered to be an important driver to increase phenotypic variation, but diversity may also be constrained by historical factors related to colonization events. How do ecological opportunity and post-glacial colonization history affect the phenotypic diversity in a young species lineage? We quantified phenotypic diversity ...

We explore the long-term developments in population biology and life history during the invasion and establishment of the fish species vendace Coregonus albula in a subarctic watercourse by comparing life-history traits and molecular genetic estimates between the source and the colonist population. The two populations exhibited highly contrasting life-history strategies. Relative to the source ...

Morphological divergence was evident among three sympatric morphs of Arctic charr (Salvelinus alpinus (L.)) that are ecologically diverged along the shallow-, deep-water resource axis in a subarctic postglacial lake (Norway). The two deep-water (profundal) spawning morphs, a benthivore (PB-morph) and a piscivore (PP-morph), have evolved under identical abiotic conditions with constant low light ...

Parasite−host systems show markedly variable patterns in isotopic fractionation: parasites can be either depleted or enriched in 15N and 13C as compared to their hosts. However, it remains unknown whether isotopic fractionation patterns are similar in comparable parasite−host systems from markedly different ecosystems. Results of this study show that large-sized Schistocephalus spp. endoparasites ...

Arctic charr and European whitefish are considered to be strong competitors in lakes, with the latter usually being the superior species. However, high niche plasticity and lake morphometry may suggestively facilitate resource partitioning and coexistence between charr and whitefish. Here, we explore the trophic niche utilization (diet and habitat use) of charr and whitefish co-occurring with brown ...