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Habitat Differentiation (habitat + differentiation)
Selected AbstractsHabitat differentiation within the large-carnivore community of Norway's multiple-use landscapesJOURNAL OF APPLIED ECOLOGY, Issue 5 2008Roel May Summary 1The re-establishment of large carnivores in Norway has led to increased conflicts and the adoption of regional zoning for these predators. When planning the future distribution of large carnivores, it is important to consider details of their potential habitat tolerances and strength of inter-specific differentiation. We studied differentiation in habitat and kill sites within the large-carnivore community of south-eastern Norway. 2We compared habitat selection of the brown bear Ursus arctos L., Eurasian lynx Lynx lynx L., wolf Canis lupus L. and wolverine Gulo gulo L., based on radio-tracking data. Differences in kill site locations were explored using locations of documented predator-killed sheep Ovis aries L. We modelled each species' selection for, and differentiation in, habitat and kill sites on a landscape scale using resource selection functions and multinomial logistic regression. Based on projected probability of occurrence maps, we estimated continuous patches of habitat within the study area. 3Although bears, lynx, wolves and wolverines had overlapping distributions, we found a clear differentiation for all four species in both habitat and kill sites. The presence of bears, wolves and lynx was generally associated with rugged, forested areas at lower elevations, whereas wolverines selected rugged terrain at higher elevations. Some degree of sympatry was possible in over 40% of the study area, although only 1·5% could hold all four large carnivores together. 4Synthesis and applications. A geographically differentiated management policy has been adopted in Norway, aimed at conserving viable populations of large carnivores while minimizing the potential for conflicts. Sympatry of all four carnivores will be most successful if regional zones are established of adequate size spanning an elevational gradient. High prey densities, low carnivore densities, low dietary overlap and scavenging opportunities have most probably led to reduced competitive exclusion. Although regional sympatry enhances the conservation of an intact guild of large carnivores, it may well increase conflict levels and resistance to carnivore conservation locally. [source] Patterns, sources and ecological implications of clonal diversity in apomictic Ranunculus carpaticola (Ranunculus auricomus complex, Ranunculaceae)MOLECULAR ECOLOGY, Issue 4 2006O. PAUN Abstract Sources and implications of genetic diversity in agamic complexes are still under debate. Population studies (amplified fragment length polymorphisms, microsatellites) and karyological methods (Feulgen DNA image densitometry and flow cytometry) were employed for characterization of genetic diversity and ploidy levels of 10 populations of Ranunculus carpaticola in central Slovakia. Whereas two diploid populations showed high levels of genetic diversity, as expected for sexual reproduction, eight populations are hexaploid and harbour lower degrees of genotypic variation, but maintain high levels of heterozygosity at many loci, as is typical for apomicts. Polyploid populations consist either of a single AFLP genotype or of one dominant and a few deviating genotypes. genotype/genodive and character incompatibility analyses suggest that genotypic variation within apomictic populations is caused by mutations, but in one population probably also by recombination. This local facultative sexuality may have a great impact on regional genotypic diversity. Two microsatellite loci discriminated genotypes separated by the accumulation of few mutations (,clone mates') within each AFLP clone. Genetic diversity is partitioned mainly among apomictic populations and is not geographically structured, which may be due to facultative sexuality and/or multiple colonizations of sites by different clones. Habitat differentiation and a tendency to inhabit artificial meadows is more pronounced in apomictic than in sexual populations. We hypothesize that maintenance of genetic diversity and superior colonizing abilities of apomicts in temporally and spatially heterogeneous environments are important for their distributional success. [source] Sea cucumber habitat differentiation and site retention as determined by intraspecific stable isotope variationAQUACULTURE RESEARCH, Issue 10 2010Matthew J Slater Abstract Stable carbon and nitrogen isotope ratios (,13C/,15N) were assessed as a means to ascertain the recent in situ feeding history of the common New Zealand sea cucumber Australostichopus mollis in relation to nutrient enrichment from a longline green-lipped mussel (Perna canaliculus) farm in Northern New Zealand. ,13C and ,15N isotopic signatures and the ratios of sea cucumbers sampled from within the impact footprint of the mussel farm were compared with those of sea cucumbers residing on adjacent natural reefs. Sea cucumbers from beneath mussel farming longlines had significantly different ,13C stable isotope signatures in comparison with sea cucumbers collected from neighbouring natural reef habitats. This difference supports the hypothesis that sea cucumbers in the same bay maintain distinctly different feeding histories, with those residing beneath mussel farming longlines deriving tissue carbon from sediment impacted by farming activities. This hypothesis is further supported by the finding that the isotope signature of sediment collected from beneath the mussel farm is consistent with the expectation that sea cucumbers were feeding on and consuming sediment enriched with bivalve waste (faeces and pseudo-faeces). In contrast, the nitrogen stable isotope signature (,15N) was found to be similar between sites for both sea cucumbers and assumed food sources. Both findings lend support to the viability of future sea cucumber/green-lipped mussel farm polyculture systems. Sea cucumbers in different locations (mussel farm, natural reef) possessed distinctly different isotope signatures, suggesting that mixing of sea ranched sea cucumbers with natural reef populations would be negligible or non-existent. Similarities between the isotope signatures in low metabolic tissue of sea cucumbers residing at the mussel farm site to that of mussel farm-impacted sediment suggest that cucumbers beneath mussel farms appear to have high rates of retention at the farm site. [source] Environmental changes in man-made coastal dune pools since 1850 as indicated by sedimentary and epiphytic diatom assemblages (Belgium)AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2003Luc Denys Abstract 1.Diatom assemblages of man-made coastal dune wetlands between Blankenberge and Heist (Belgium), dating from 1852 to 1929 and sampled from herbarium specimens of macrophytes, were compared with more recent samples collected in the remaining calcareous dune marshes and pools in this area. 2.Overall, nutrient conditions inferred from the reference assemblages were fairly eutrophic for phosphorus. Only a minority of the historical assemblages pointed to presumably nitrogen-limited conditions. 3.Significant alterations in general assemblage composition were observed, including a marked decline of epiphytic species, and a decrease in the compositional variation in sediment diatom assemblages. These changes can be attributed mainly to an increased availability of nutrients and degradable organic matter since the mid 1970s. No changes in the salinity range seem to have occurred, suggesting fairly stable hydrological conditions. 4.Possible causes for eutrophication include increased atmospheric deposition of nutrients, but also more site-related phenomena such as guanotrophication, angling and, perhaps, effects of nature management on soil,nutrient cycling. Their relative importance needs to be established and further monitoring is necessary. 5.Measures are required to reduce nutrient levels of both permanently and periodically inundated sites and to promote small-scale habitat differentiation. Due to physical constraints, the latter will be possible only by mimicking the processes that act upon more natural dune systems in management practice. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||