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Available Habitat (available + habitat)
Selected AbstractsA patch perspective on summer habitat use by brown trout Salmo trutta in a high plains stream in Wyoming, USAECOLOGY OF FRESHWATER FISH, Issue 3 2009R. R. O'Connor Abstract,,, We quantified the use of habitat patches by brown trout, Salmo trutta, during summer conditions in a plains stream in the western United States. A Global Positioning System was used to map discrete habitat patches (2,420 m2) consisting of macrophytes, wood accumulation, or deep water. Habitat use by brown trout was monitored by radio telemetry. Brown trout used habitat in a nonrandom manner with 99% of all daytime observations and 91% of all nighttime observations occurring in patches that consisted of combinations of deep water, wood accumulations or macrophytes even though such patches constituted only 9.8% of the available habitat. Brown trout used deep water almost exclusively during the day but broadened their habitat use at night. Most fish stayed within a large plunge pool created by a low-head dam. This pool supplemented the deep-water habitat that was naturally rare in our study area and illustrates how human modifications can sometimes create habitat patches important for stream fishes. [source] Diurnal stream habitat use of juvenile Atlantic salmon, brown trout and rainbow trout in winterFISHERIES MANAGEMENT & ECOLOGY, Issue 5 2009J. H. JOHNSON Abstract, The diurnal winter habitat of three species of juvenile salmonids was examined in a tributary of Skaneateles Lake, NY to compare habitat differences among species and to determine if species/age classes were selecting specific habitats. A total of 792 observations were made on the depth, velocity, substrate and cover (amount and type) used by sympatric subyearling Atlantic salmon, subyearling brown trout and subyearling and yearling rainbow trout. Subyearling Atlantic salmon occurred in shallower areas with faster velocities and less cover than the other salmonid groups. Subyearling salmon was also the only group associated with substrate of a size larger than the average size substrate in the study reach during both winters. Subyearling brown trout exhibited a preference for vegetative cover. Compared with available habitat, yearling rainbow trout were the most selective in their habitat use. All salmonid groups were associated with more substrate cover in 2002 under high flow conditions. Differences in the winter habitat use of these salmonid groups have important management implications in terms of both habitat protection and habitat enhancement. [source] Concurrent assessment of fish and habitat in warmwater streams in WyomingFISHERIES MANAGEMENT & ECOLOGY, Issue 1 2006M. C. QUIST Abstract, Fisheries research and management in North America have focused largely on sport fishes, but native non-game fishes have attracted increased attention due to their declines. The Warmwater Stream Assessment (WSA) was developed to evaluate simultaneously both fish and habitat in Wyoming streams by a process that includes three major components: (1) stream-reach selection and accumulation of existing information, (2) fish and habitat sampling and (3) summarisation and evaluation of fish and habitat information. Fish are sampled by electric fishing or seining and habitat is measured at reach and channel-unit (i.e. pool, run, riffle, side channel, or backwater) scales. Fish and habitat data are subsequently summarised using a data-matrix approach. Hierarchical decision trees are used to assess critical habitat requirements for each fish species expected or found in the reach. Combined measurements of available habitat and the ecology of individual species contribute to the evaluation of the observed fish assemblage. The WSA incorporates knowledge of the fish assemblage and habitat features to enable inferences of factors likely influencing both the fish assemblage and their habitat. The WSA was developed for warmwater streams in Wyoming, but its philosophy, process and conceptual basis may be applied to environmental assessments in other geographical areas. [source] Upward range extension of Andean anurans and chytridiomycosis to extreme elevations in response to tropical deglaciationGLOBAL CHANGE BIOLOGY, Issue 1 2007TRACIE A. SEIMON Abstract High-alpine life forms and ecosystems exist at the limits of habitable environments, and thus, are especially sensitive to environmental change. Here we report a recent increase in the elevational limit of anurans following glacial retreat in the tropical Peruvian Andes. Three species have colonized ponds in recently deglaciated terrain at new record elevations for amphibians worldwide (5244,5400 m). Two of these species were also found to be infected with Batrachochytrium dendrobatidis (Bd), an emerging fungal pathogen causally associated with global amphibian declines, including the disappearance of several Latin American species. The presence of this pathogen was associated with elevated mortality rates of at least one species. These results represent the first evidence of upward expansion of anurans to newly available habitat brought about by recent deglaciation. Furthermore, the large increase in the upper limit of known Bd infections, previously reported as 4112 m in Ecuador, to 5348 m in this study, also expands the spatial domain of potential Bd pathogenicity to encompass virtually all high elevation anuran habitats in the tropical Andes. [source] The discordance of diversification: evolution in the tropical-montane frogs of the Eastern Arc Mountains of TanzaniaMOLECULAR ECOLOGY, Issue 18 2010LUCINDA P. LAWSON Abstract Species with similar geographical distribution patterns are often assumed to have a shared biogeographical history, an assumption that can be tested with a combination of molecular, spatial, and environmental data. This study investigates three lineages of Hyperolius frogs with concordant ranges within the Eastern Afromontane Biodiversity Hotspot to determine whether allopatric populations of co-distributed lineages shared a parallel biogeographical response to their shared paleoclimatic histories. The roles of refugial distributions, isolation, and climate cycles in shaping their histories are examined through Hierarchical Approximate Bayesian Computation, comparative phylogeography, and comparisons of current and past geographical distributions using ecological niche models. Results from these analyses show these three lineages to have independent evolutionary histories, which current spatial configurations of sparsely available habitat (montane wetlands) have moulded into convergent geographical ranges. In spite of independent phylogeographical histories, diversification events are temporally concentrated, implying that past vicariant events were significant at the generic level. This mixture of apparently disparate histories is likely due to quantifiably different patterns of expansion and retreat among species in response to past climate cycles. Combining climate modelling and phylogeographical data can reveal unrecognized complexities in the evolution of co-distributed taxa. [source] The role of migration for spatial turnover of arctic bird species in a circumpolar perspectiveOIKOS, Issue 11 2008Sara Henningsson Several different factors may determine where species range limits are located within regions of otherwise continuously available habitat and suitable climate. Within the Arctic tundra biome many bird species are migratory and their breeding distributions are affected by migration routes that are in turn limited by factors such as suitable winter habitat, migratory stopover sites, geographical barriers and historical routes of colonization. We identified longitudinal zones in the circumpolar Arctic of pronounced changes in the avian species composition (high species spatial turnover; ,species divides'). We tested for the association between migratory status and the geographical location and numbers of such species divides for species with non-breeding habitats mainly within terrestrial, pelagic and coastal ecosystems. Our results demonstrate that migration is of profound importance for both the number and locations of species divides in the Arctic. Long-distance migration is associated with a large number of divides among terrestrial and coastal arctic birds but with a reduced number of divides among pelagic birds. We suggest that long-distance migration permits pelagic but not terrestrial and coastal birds to colonize large winter ranges, which in turn causes expansion of breeding ranges, with more homogenous communities and reduction of species divides as consequences, among the long-distance migrants of pelagic but not of terrestrial and coastal birds. Furthermore, the divides among long-distance migrants are situated in two main regions, the Beringia and Greenland zones, while divides among short-distance migrants are more evenly spaced throughout the circumpolar Arctic. The Beringia and Greenland divides result largely from inter-continental colonization of new breeding ranges but retainment of original winter quarters in a process of evolution through extension of migration routes, leading to aggregated divides in the meeting zones of major global flyways. [source] Rangeland degradation is poised to cause Africa's first recorded avian extinctionANIMAL CONSERVATION, Issue 3 2009C. N. Spottiswoode Abstract Rangeland degradation by livestock threatens several restricted-range species, but is largely overlooked by conservation biologists. The Sidamo lark Heteromirafra sidamoensis, confined to the Liben Plain grassland in southern Ethiopia, is critically endangered by bush encroachment, permanent settlement and agricultural conversion. Its global range was previously estimated at 760 km2, but in 2007,2008 available habitat covered<35 km2. Density estimates from multi-model inference analysis of distance transect data provided a global population estimate of 90,256 adults (possibly with a serious sex-ratio bias towards males). Logistic regression models of habitat selection showed that males preferentially occurred in areas of grassland with greater cover of medium-length grass (5,15 cm), less cover of bare ground and fewer bushes. Habitat transects extending outward from its core range revealed massive and rapid bush encroachment, corroborating information from semi-structured interviews. The survival of both local Borana pastoralism and this species , mainland Africa's likeliest first avian extinction , depends on restoring seasonal patterns of grazing, resisting agricultural conversion of grasslands, reversing fire suppression policies and clearing bush. [source] Edaphic niche differentiation among Polybotrya ferns in western Amazonia: implications for coexistence and speciationECOGRAPHY, Issue 3 2006Hanna TuomistoArticle first published online: 22 FEB 200 To study the degree of edaphic specialization in Amazonian plants, the distribution patterns of seven species of Polybotrya ferns were studied in 109 sites in a climatically uniform area of northwestern Amazonia (Colombia, Ecuador and northern Peru). The two most abundant species of Polybotrya were found in about two-thirds of the sites with almost 7000 individuals each, the rarest species occurred in just one site with 40 individuals. Each of the seven species appeared to have a unique realised niche, when niche dimensions were defined by gradients in soil texture, soil cation content, and inundation. The species also differed in how broadly or narrowly they were distributed along each gradient. Some species were practically never found in the same sites, whereas others co-occurred with a high frequency, in spite of showing clearly different abundance patterns among sites. A single site only contains a small part of the edaphic variation present in the landscape, and a small proportion of any species' niche space, so broad-scale studies are needed to adequately describe and compare species' niches and to assess to what degree niche differences promote species coexistence. The distribution patterns in Polybotrya are consistent with, but do not prove, that ecological speciation may have been important in the radiation of the genus. If such a pattern is found to be common in other Amazonian plants, this would indicate that each evolutionary lineage has adapted to the available habitats largely independently of the others. [source] Phylogeographical structure, postglacial recolonization and barriers to gene flow in the distinctive Valais chromosome race of the common shrew (Sorex araneus)MOLECULAR ECOLOGY, Issue 4 2002N. Lugon-Moulin Abstract Using one male-inherited and eight biparentally inherited microsatellite markers, we investigate the population genetic structure of the Valais chromosome race of the common shrew (Sorex araneus) in the Central Alps of Europe. Unexpectedly, the Y-chromosome microsatellite suggests nearly complete absence of male gene flow among populations from the St-Bernard and Simplon regions (Switzerland). Autosomal markers also show significant genetic structuring among these two geographical areas. Isolation by distance is significant and possible barriers to gene flow exist in the study area. Two different approaches are used to better understand the geographical patterns and the causes of this structuring. Using a principal component analysis for which testing procedure exists, and partial Mantel tests, we show that the St-Bernard pass does not represent a significant barrier to gene flow although it culminates at 2469 m, close to the highest altitudinal record for this species. Similar results are found for the Simplon pass, indicating that both passes represented potential postglacial recolonization routes into Switzerland from Italian refugia after the last Pleistocene glaciations. In contrast with the weak effect of these mountain passes, the Rhône valley lowlands significantly reduce gene flow in this species. Natural obstacles (the large Rhône river) and unsuitable habitats (dry slopes) are both present in the valley. Moreover, anthropogenic changes to landscape structures are likely to have strongly reduced available habitats for this shrew in the lowlands, thereby promoting genetic differentiation of populations found on opposite sides of the Rhône valley. [source] Habitat selection by the swamp wallaby (Wallabia bicolor) in relation to diel period, food and shelterAUSTRAL ECOLOGY, Issue 2 2009JULIAN DI STEFANO Abstract Patterns of resource selection by animals may be influenced by sex, and often change over a 24-h period. We used a dry sclerophyll landscape managed for commercial timber production to investigate the effects of sex and diel period on habitat selection by the swamp wallaby (Wallabia bicolor). We predicted that selection would be (i) affected by both sex and diel period; and (ii) positively related to lateral cover during the day, but to food resources at night. Non-metric multidimentional scaling indicated that some of the available habitats differed markedly with respect to visibility (an indicator of lateral cover), fern cover, forb cover, wallaby density and a forage quality index, providing the basis for non-random habitat selection. At the landscape scale, wallabies showed strong selection for 5-year-old regenerating sites, selected against 10-year-old regenerating sites and unharvested forest, and avoided recently harvested (3,10 months post-harvest) sites completely. At the scale of individual home ranges, a pooled male and female sample demonstrated selection for unharvested forest over recently harvested sites during both diurnal and nocturnal periods. A separate analysis showed that both sex and diel period influenced the selection of 5- and 10-year-old sites and the surrounding unharvested forest. Using a novel approach, we demonstrated that diurnal habitat selection by both sexes was negatively correlated with visibility, representing stronger selection for areas with more lateral cover. Nocturnal selection by females was positively correlated with values of a forage quality index, but this was not the case for males. We hypothesise that the observed patterns of selection were driven by the need to find food and avoid predators, but were also affected by the different reproductive strategies of males and females. Our results demonstrate the importance of incorporating factors such as sex and diel period into analyses of habitat selection. [source] | ||||||||||||||||||||||