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Unsuitable Habitat (unsuitable + habitat)
Selected AbstractsComputer-generated null models as an approach to detect perceptual range in mark,re-sight studies , an example with grasshoppersECOLOGICAL ENTOMOLOGY, Issue 2 2005Silke Hein Abstract., 1. Dispersal and habitat detection are key factors for the colonisation of habitat fragments in heterogeneous landscapes. The ability to recognise a habitat from a certain distance should increase the survival chances of a dispersing individual; however, due to methodological problems there is little information on the perceptual range of most species. 2. In a field experiment, 44 individually marked grasshoppers of the species Oedipoda caerulescens (Orthoptera: Acrididae: Locustinae) were released into an unfamiliar, hostile environment at various distances from a patch of preferred habitat. 3. Whether individuals reached the habitat or not was measured, as well as the daily movement distances. The number of individuals that reached the habitat was tested against computer-generated predictions based on different underlying rules for the movement behaviour of individuals but not accounting for the ability to detect habitat from distance. 4. On the first day a significantly higher proportion of grasshoppers arrived in the habitat than predicted by any of the null models. 5. It was concluded that individuals of O. caerulescens are able to detect their preferred habitat from a distance. 6. Edge permeability was very low as none of the individuals left the habitat once they had reached it. 7. Additional analyses showed that individuals changed movement behaviour from a directed walk with great daily distances in unsuitable habitat to a walk with significantly shorter daily distances within the preferred habitat. 8. The problems that arose in the field experiment are discussed and recommendations are given for further studies. [source] On the relationship between niche and distributionECOLOGY LETTERS, Issue 4 2000H.R. Pulliam Applications of Hutchinson's n -dimensional niche concept are often focused on the role of interspecific competition in shaping species distribution patterns. In this paper, I discuss a variety of factors, in addition to competition, that influence the observed relationship between species distribution and the availability of suitable habitat. In particular, I show that Hutchinson's niche concept can be modified to incorporate the influences of niche width, habitat availability and dispersal, as well as interspecific competition per se. I introduce a simulation model called NICHE that embodies many of Hutchinson's original niche concepts and use this model to predict patterns of species distribution. The model may help to clarify how dispersal, niche size and competition interact, and under what conditions species might be common in unsuitable habitat or absent from suitable habitat. A brief review of the pertinent literature suggests that species are often absent from suitable habitat and present in unsuitable habitat, in ways predicted by theory. However, most tests of niche theory are hampered by inadequate consideration of what does and does not constitute suitable habitat. More conclusive evidence for these predictions will require rigorous determination of habitat suitability under field conditions. I suggest that to do this, ecologists must measure habitat specific demography and quantify how demographic parameters vary in response to temporal and spatial variation in measurable niche dimensions. [source] A metapopulation perspective for salmon and other anadromous fishFISH AND FISHERIES, Issue 4 2007Nicolas Schtickzelle Abstract Salmonids are an important component of biodiversity, culture and economy in several regions, particularly the North Pacific Rim. Given this importance, they have been intensively studied for about a century, and the pioneering scientists recognized the critical link between population structure and conservation. Spatial structure is indeed of prime importance for salmon conservation and management. At first glance, the essence of the metapopulation concept, i.e. a population of populations, widely used on other organisms like butterflies, seems to be particularly relevant to salmon, and more generally to anadromous fish. Nevertheless, the concept is rarely used, and barely tested. Here, we present a metapopulation perspective for anadromous fish, assessing in terms of processes rather than of patterns the set of necessary conditions for metapopulation dynamics to exist. Salmon, and particularly sockeye salmon in Alaska, are used as an illustrative case study. A review of life history traits indicates that the three basic conditions are likely to be fulfilled by anadromous salmon: (i) the spawning habitat is discrete and populations are spatially separated by unsuitable habitat; (ii) some asynchrony is present in the dynamics of more or less distant populations and (iii) dispersal links populations because some salmon stray from their natal population. The implications of some peculiarities of salmon life history traits, unusual in classical metapopulations, are also discussed. Deeper understanding of the population structure of anadromous fish will be advanced by future studies on specific topics: (i) criteria must be defined for the delineation of suitable habitats that are based on features of the biotope and not on the presence of fish; (ii) the collection of long-term data and the development of improved methods to determine age structure are essential for correctly estimating levels of asynchrony between populations and (iii) several key aspects of dispersal are still poorly understood and need to be examined in detail: the spatial and temporal scales of dispersal movements, the origin and destination populations instead of simple straying rates, and the relative reproductive success of immigrants and residents. [source] Climate warming causes phenological shift in Pink Salmon, Oncorhynchus gorbuscha, behavior at Auke Creek, AlaskaGLOBAL CHANGE BIOLOGY, Issue 2 2008SIDNEY G. TAYLORArticle first published online: 23 NOV 200 Abstract Thirty-four years (1972,2005) of water temperature data and extensive biological observations at Auke Creek, Alaska indicate a general warming trend that affected the native pink salmon (Oncorhynchus gorbuscha) population. Serial environmental records at nearby Auke Bay, Alaska over 46 years show trends of increasing air and sea surface temperatures. Trends of increased total precipitation and earlier date of ice out on nearby Auke Lake also occurred, but not at significant rates. Average water temperatures during the incubation of pink salmon in Auke Creek increased at a rate of 0.03 °C yr,1 over the 34-year period. For the 1972,2005 broods, midpoints of fry migrations from Auke Creek ranged between April 2 and May 7, and there was a trend of earlier migration of pink salmon fry at a rate of , 0.5 days yr,1. The migration timing of adult salmon into Auke Creek also showed a trend toward earlier timing. The earlier adult migration combined with warmer incubation temperatures are related to earlier migration of pink salmon fry. If the observed warming trend continues, Auke Creek may become unsuitable habitat for pink salmon. Given the trend for salmon fry to migrate earlier, a larger portion of the population may become mismatched with optimum environmental conditions during their early marine life history. If salmon adults continue to migrate into the creek earlier when water temperatures are commonly high, it will result in increased prespawning mortality. [source] Modelling past and present geographical distribution of the marine gastropod Patella rustica as a tool for exploring responses to environmental changeGLOBAL CHANGE BIOLOGY, Issue 10 2007FERNANDO P. LIMA Abstract A climate envelope approach was used to model the distributions of the intertidal gastropod Patella rustica, to test the robustness of forecast responses to climate change. The model incorporated variables that were likely to determine the abundance and the northern range limit of this species in the NE Atlantic. The model was built using classification and regression tree analysis (CART) trained with historical distribution data from the mid 1950s and a set of corresponding climatic and oceanographic variables. Results indicated air and sea temperature, in particular during the reproductive and settlement periods, as the main determinants of the Atlantic distribution of P. rustica. The model was subsequently fed with contemporary climatic data and its output was compared with the current distribution and abundance of P. rustica, assessed during a 2002,2003 survey. The model correctly hindcasted the recent collapse of a distributional gap in northern Portugal, as well as an increase in abundance at locations within its range. The predicted northward expansion of the northern range limit did not occur because the absence of the species was confirmed in a survey encompassing the whole Atlantic French coast up to Brest. Stretches of unsuitable habitat too long to be overcome by dispersal are the likely mechanism controlling the northern limit of the distribution of this intertidal species. [source] Habitat heterogeneity influences connectivity in a spatially structured pest populationJOURNAL OF APPLIED ECOLOGY, Issue 2 2006G. S. HAMILTON Summary 1Patterns of connectivity influence pest population system dynamics, and it is essential to consider connectivity when planning effective management strategies. Traditional connectivity models often consider populations embedded in a matrix of unsuitable habitat. This approach is unlikely to be applicable to those pest species that can utilize most of the landscape in which they live. There is therefore a need for a simple and flexible tool to assess connectivity in such systems. 2In this study, we developed a new model in which contiguous resource patches that differ in quality, and landscape elements that impede dispersal, impact on connectivity within a population system. The model was applied to a wild rabbit population system, a well-studied pest species in Australia. An independent population genetic data set was used to validate the model. 3There was a highly significant association between pairwise population connectivity and the genetic data (Mantel test, r=,0·502, P= 0·002). As predicted, two populations that showed very low connectivity were strongly isolated genetically. These sites appeared to be substantially isolated because of forests, which acted to impede rabbit dispersal. When these sites were excluded from analysis, connectivity indices again explained the pattern of genetic data (Mantel test, r=,0·46, P= 0·037). This showed that both spatial variation in resource quality and forests influenced connectivity in this system. Sensitivity analyses confirmed that the distribution and extent of forests was important in limiting connectivity to some sites. The model was relatively robust to changes in population parameters. 4Synthesis and applications. Connectivity among wild rabbit populations in this system was strongly influenced by habitat heterogeneity, rather than factors such as geographical distance or major landscape elements such as rivers, both of which are traditionally considered to influence system dynamics. This may have substantial implications for many pest systems, and suggests that the impact of habitat heterogeneity on connectivity should be considered when planning efficient management strategies. [source] Modelling the distribution of a threatened habitat: the California sage scrubJOURNAL OF BIOGEOGRAPHY, Issue 11 2009Erin C. Riordan Abstract Aim, Using predictive species distribution and ecological niche modelling our objectives are: (1) to identify important climatic drivers of distribution at regional scales of a locally complex and dynamic system , California sage scrub; (2) to map suitable sage scrub habitat in California; and (3) to distinguish between bioclimatic niches of floristic groups within sage scrub to assess the conservation significance of analysing such species groups. Location, Coastal mediterranean-type shrublands of southern and central California. Methods, Using point localities from georeferenced herbarium records, we modelled the potential distribution and bioclimatic envelopes of 14 characteristic sage scrub species and three floristic groups (south-coastal, coastal,interior disjunct and broadly distributed species) based upon current climate conditions. Maxent was used to map climatically suitable habitat, while principal components analysis followed by canonical discriminant analysis were used to distinguish between floristic groups and visualize species and group distributions in multivariate ecological space. Results, Geographical distribution patterns of individual species were mirrored in the habitat suitability maps of floristic groups, notably the disjunct distribution of the coastal,interior species. Overlap in the distributions of floristic groups was evident in both geographical and multivariate niche space; however, discriminant analysis confirmed the separability of floristic groups based on bioclimatic variables. Higher performance of floristic group models compared with sage scrub as a whole suggests that groups have differing climate requirements for habitat suitability at regional scales and that breaking sage scrub into floristic groups improves the discrimination between climatically suitable and unsuitable habitat. Main conclusions, The finding that presence-only data and climatic variables can produce useful information on habitat suitability of California sage scrub species and floristic groups at a regional scale has important implications for ongoing efforts of habitat restoration for sage scrub. In addition, modelling at a group level provides important information about the differences in climatic niches within California sage scrub. Finally, the high performance of our floristic group models highlights the potential a community-level modelling approach holds for investigating plant distribution patterns. [source] Dispersal and phylogeography of the agamid lizard Amphibolurus nobbi in fragmented and continuous habitatMOLECULAR ECOLOGY, Issue 6 2005D. A. DRISCOLL Abstract Approximately 90% of native vegetation has been cleared for agriculture in central New South Wales, Australia. Habitat loss has reduced and fragmented populations of the agamid lizard Amphibolurus nobbi. We compared genetic structure of populations of this species in an unmodified landscape with those from small nature reserves and linear remnants in farming areas. We ask: Is there evidence for reduced dispersal and population fragmentation among farm populations? Using 2008 bp mtDNA sequences and allozyme electrophoresis, we found that small populations in farming areas had as much genetic variation as populations in nature reserves. Application of nested clade analysis (NCA) indicated isolation-by-distance effects among populations from uncleared areas, but not among populations within farming locations. The genetic evidence therefore implied a high level of migration in the cleared landscapes. High dispersal after fragmentation may have resulted from either a burst of movement at the time of land clearing with dragons from many sources finding refuge in a few remnants, or from ongoing rapid dispersal through unsuitable habitat. A phylogeny based on mtDNA revealed that A. nobbi populations in the study area are deeply divided into two reciprocally monophyletic groups. Although we did not sample the entire species range, one of these evolutionarily significant units was only detected in remnant vegetation in the agricultural landscape. Therefore, a substantial subclade of this species may be vulnerable to extinction. Our findings emphasize that local populations of widespread species can harbour important intraspecific genetic diversity, supporting the case for maintaining widespread species throughout production landscapes. [source] Constraints on home range behaviour affect nutritional condition in urban house sparrows (Passer domesticus)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010CARL VANGESTEL In human-dominated landscapes (semi)natural habitats are typically embedded in tracts of unsuitable habitat. Under such conditions, habitat characteristics and grain size of the surrounding landscape may affect how much food, and at what cost, is available for sedentary species with low home-range plasticity. Here we combine behavioural radio-tracking, feather ptilochronology, and landscape analysis to test how nutritional condition varies with home range size in 13 house sparrow [Passer domesticus (Linnaeus, 1758)] populations along an urban gradient. Urban individuals occupied smaller home ranges than conspecifics from rural areas, most distinctly if key cover was highly scattered. In urban plots, patch connectivity, home range sizes, and activity areas were positively correlated, indicating that individual ranging behaviour was related to the spatial distribution of suitable habitat. Urban House sparrows also showed the smallest feather growth bars, which were positively related to home range size at plot level. In contrast, growth bar widths and home range sizes were negatively related in rural populations, whereas in suburban populations, both variables varied independently. We conclude that individuals from progressively more built-up areas show a restricted ability to adjust their daily ranging behaviour to the scattered distribution of critical resources. This may complement other putative causes of the widespread population decline of urban house sparrows. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 41,50. [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] | ||||||||||