Multi-indicator evidence for habitat use and trophic strategy segregation of two sympatric forms of Arctic char from the Cumberland Sound region of Nunavut, Canada

We analyzed Arctic Char stable isotope ratios and fatty acid composition from two geographically proximal Nunavut lakes, Qasigiyat and Iqalugaarjuit, to determine if anadromous and resident Arctic char occupied different trophic niches. Resident Arctic char had lower δ13C and δ34S, indicative of a freshwater feeding, compared to anadromous individuals. Significantly lower δ15N of residents suggests the ecotypes feed at different trophic levels. Significantly wider δ13C and δ15N ranges in residents implied a broader trophic niche or a wider range in baseline prey isotope values. Results also provide further evidence for resident use of the estuarine environment in Qasigiyat. Immature Arctic char occupy a different trophic niche than both resident and anadromous fish within Iqalugaarjuit, but this relationship is less clear in Qasigiyat. Distinct stable isotope and fatty acid profiles indicate that resident and anadromous Arctic char have distinct trophic niches, marine for anadromous, freshwater for resident. Immature Arctic char seem to occupy a distinct niche from both anadromous and resident fish, which likely relates to use of both freshwater and estuarine environments, depending on developmental stage. We show the first evidence of the fatty acid differences and niche segregation between sympatric anadromous and resident ecotypes in Arctic Char.

ДОЛГОВРЕМЕННАЯ ДИНАМИКА ОСНОВНЫХ КОМПОНЕНТОВ ЭКОСИСТЕМЫ ОЗЕРА КУЭТСЪЯРВИ (СИСТЕМА РЕКИ ПАСВИК, МУРМАНСКАЯ ОБЛАСТЬ)

The lake Kuotsjarvi (lower course of Pasvik River, Murmansk Oblast) is located in the borderline territory between Russia and Norway. It one of the most polluted water bodies of European Arctic. Because of the the metallurgic plant Pechenganikel located at the coast of the lake is the source, water and bottom sediments of the lake contain extremely high levels of heavy metals. Long-term comprehensive studies of the ecosystem of the lake revealed that the responses of its ecosystem to global and regional environmental and climatic changes include an increasing toxicity and eutrophication of lake water, decreasing number of stenobiont aqueous species and increasing numbers of ubiquistic and invasive species. The present-time communities in the lake developed as results of interactions between long-term changes in abiotic and biotic factors. Pollution with heavy metals, which lasts since 1990-ies, resulted in the development of communities of species that are tolerant to this impact and are able to maintain their abundance. Adaptations of the communities to changes in their environments are manifested as changes in their species compositions, in proportions of different taxonomic groups, and structures of their populations. In particular, whitefish is able to remain the dominant species and sustain its populations due to development of sympatric forms differing in their ecological niches, morphological features, and life cycle strategies, including transition to shorter life cycles. At difference from changes at the levels of organisms, responses of populations and communities to medium-term environmental changes are more inertial and less specific.

Adaptive radiation of barbs of the genus Labeobarbus (Cyprinidae) in the East African river

Large African barbs of the genus Labeobarbus are widely distributed in African freshwaters, and exhibit profound phenotypic plasticity that could be a prerequisite for adaptive radiation. Using morphological, molecular, and stable isotope analyses, we investigated whether an adaptive radiation has occurred in a riverine assemblage of the L. gananensis complex. This complex is composed of six phenotypically distinct sympatric forms inhabiting the Genale River (Ethiopian highlands, East Africa). Of the six forms, five were divergent in their mouth morphology, corresponding to ‘generalized’, ‘lipped’, ‘scraping’ (two forms) and ‘large-mouthed’ phenotypes. Stable isotope analysis revealed differences in 15N and 13C among these forms, representing different foraging strategies (omnivorous, scraping and piscivorous). Phylogenetic analysis of two mtDNA markers confirmed the monophyly of L. gananensis, suggesting an intra-riverine radiation. However, the Genale assemblage appears to have originated through a combination of allopatric and sympatric events. Some of the specialized forms within this drainage originated independently from the local generalized forms in three different river regions within local ‘mini-flocks’ composed of two to three sympatric forms. Our study shows that adaptive radiation in rivers can be enhanced by a combination of sympatric speciation and temporal geographic isolation, leading to local sympatric speciation followed by migration.

More than meets the eye: diversity and geographic patterns in sea cucumbers

Estimates for the number of species in the sea vary by orders of magnitude. Molecular taxonomy can greatly speed up screening for diversity and evaluating species boundaries, while gaining insights into the biology of the species. DNA barcoding with a region of cytochrome oxidase 1 (COI) is now widely used as a first pass for molecular evaluation of diversity, as it has good potential for identifying cryptic species and improving our understanding of marine biodiversity. We present the results of a large scale barcoding effort for holothuroids (sea cucumbers). We sequenced 3048 individuals from numerous localities spanning the diversity of habitats in which the group occurs, with a particular focus in the shallow tropics (Indo-Pacific and Caribbean) and the Antarctic region. The number of cryptic species is much higher than currently recognized. The vast majority of sister species have allopatric distributions, with species showing genetic differentiation between ocean basins, and some are even differentiated among archipelagos. However, many closely related and sympatric forms, that exhibit distinct color patterns and/or ecology, show little differentiation in, and cannot be separated by, COI sequence data. This pattern is much more common among echinoderms than among molluscs or arthropods, and suggests that echinoderms acquire reproductive isolation at a much faster pace than other marine phyla. Understanding the causes behind such patterns will refine our understanding of diversification and biodiversity in the sea.