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To date the studies that link community structure of benthic invertebrates with fish feeding are rare as well as factors that are behind this feeding selectivity are poorly known. In this study, we related invertebrate species composition, their dominance structure and fish biological characteristics to the feeding selectivity and overlap of the native flounder, perch and the invasive round goby in Muuga Bay, the Baltic Sea. Species composition and proportion of benthic invertebrates in the diet of fishes differed from what was available in the field. Except for the round goby, the studied fishes preferred small and mobile invertebrates over large bivalves. However, diet of the studied species, namely the round goby and flounder overlapped. Besides, perch preyed on young stages of the round goby indicating that the introduction of round goby may negatively affect flounder but positively perch.
We describe eight new micro satellite loci for hawkmoths of the Hyles euphorbiae complex. They are polymorphic (except for one locus in one population) with 2–18 alleles per locus, an expected heterozygosity between 0.14 and 0.94, and an observed heterozygosity between 0.10 and 0.75. As typical for Lepidoptera, the yield of new loci was low due to the presence of microsatellite gene families and variable flanking regions. These microsatellites provide informative results in population studies of the West Palearctic H. euphorbiae complex since cross amplification for H. euphorbiae and H. tithymali was successful for all but one locus.
Coturnix coturnix is a climatically widespread farmland specialist bird with a well-known distribution in the Iberian Peninsula. Therefore, its current real distribution can be finely mapped. We used recent atlas data and high-resolution climate layers to model the climatic distribution of this species. Next, we compared the obtained predictive maps with the real distribution of the species. Precise information about underestimation and overestimation of model predictions at different sample sizes was obtained. An increase in sample size allowed the predicted distribution to approach the current real distribution, but unbalanced the climatic prediction. This is because the distribution of occurrences is mostly determined by habitat, which depends more on agricultural factors and less on climate. Modelling the climatic distribution of widespread species while ignoring habitat constraints could lead to a non-equilibrium scenario where obtained predictions may not be reliable.
Empirical evidence does not fully support the universal nature of the positive interspecific abundance—distribution relationship. We have earlier documented a negative relationship for butterfly species in Finland, but recently our view was again challenged using a small subset of Finnish butterflies as apparent evidence. Here we scrutinize the critique and identify some general conceptual challenges in analyses of interspecific abundance—distribution relationships. We identify the common problem that the abundance—distribution studies include only a small subset of species, and thus reveal only sample characteristics, not overall patterns in complete assemblages. Small subsets of species are also unlikely to have sufficient power to reveal nonlinear relationships. Second, varying definitions of abundance, especially the practice of using a single point estimate to describe average density, further spur the empirical evidence for the abundance—distribution relationship. To get theoretically relevant results abundance and distribution must be defined and operationalised consistently; otherwise macroecology will reduce to simple documentation of ambiguous patterns and aid little in understanding the biological world.
Cyclic dynamics with extensive spatial synchrony has long been regarded as characteristic of key herbivores at high latitudes. This contrasts to recent reports of fading cycles in arvicoline rodents in boreal and alpine Fennoscandia. We investigate the spatiotemporal dynamics of boreal red fox and alpine arctic fox in Sweden as a proxy for the dynamics of their main prey, voles and Norwegian lemming, respectively. We analyse data from five decades, 1960–2008, with wavelets and autocorrelation approaches. Cyclic dynamics were identified with at least one method in all populations (arctic fox n = 3, red fox n = 6). The dynamics were synchronous between populations, or coupled with a 1-yr lag, in 8 of 13 pairwise comparisons. Importantly though, the dynamics were heterogeneous in space and time. All analytical approaches identified fading cycles in the three arctic fox populations and two northern red fox populations. At least one method identified similar patterns in three southern red fox populations. Red fox dynamics were cyclic in the 1970s primarily, while arctic fox dynamics was cyclic until the late 1980s or early 1990s. When cyclic, 4-yr cycles dominated in arctic fox and northern red fox, whilst 3–4-yr cycles was found in southern red foxes. Significant cyclic regimes reappeared in the 1990s or 2000s in two red fox populations and one arctic fox population. Cycles and regionally coupled dynamics appeared associated in northern arctic and red foxes. This study supports accumulating evidence which suggests that cyclic and synchronous patterns in the dynamics of lemmings and voles are nonstationary in space and time. Furthermore, the similar patterns of change in both fox species indicate that persistence of cycles is governed by similar mechanisms in lemmings and voles.
The niche variation hypothesis suggests that a population's ability to react to varying environmental conditions depend on the behavioural variability of its members. However, most studies on bats, including the work on the habitat use of the western barbastelle bat, Barbastella barbastellus, have not considered sex-specific and individual variability. We studied the habitat use of 12 female and five male western barbastelle bats within their home ranges with respect to available habitat types by applying kernel methods and Euclidean distances. Our results indicate individual habitat preferences within and among sexes of this species. Females preferred deciduous forest and linear elements within the forest. Males used habitat patches in the vicinity of the maternity colony and preferred forest edges and open habitats. Our results strongly suggest that both sexes' as well as individual variability in habitat choice are to be considered to assess a population's true potential to react on habitat alterations.