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Source Habitat (source + habitat)
Selected AbstractsThe effects of dispersal and recruitment limitation on community structure of odonates in artificial pondsECOGRAPHY, Issue 4 2006Shannon J. McCauley I examined the effects of isolation on the structure of both adult and larval dragonfly (Odonata: Anisoptera) communities forming at physically identical artificial ponds over two years. Isolation, whether measured by distance to the nearest source habitat or by connectivity to multiple sources, was significantly negatively related to the species richness of dragonflies observed at and collected in these ponds. These results indicate that dispersal and recruitment limitation acted as filters on the richness of communities at these artificial ponds. The richness of larval recruits in artificial ponds was lower than the richness of adult dispersers observed at ponds, and distance from a source habitat explained a greater fraction of the variation in larval than adult richness (83 and 50%, respectively). These results and a male biased sex-ratio in adults observed at artificial ponds suggest that isolated habitats may be more recruitment limited than observations of dispersers would suggest. A Mantel test indicated there was a spatial component to the composition of communities forming in tanks, and that distance between tanks and community dissimilarity (1-Jaccard's) were significantly positively related (r=0.52). This pattern suggests that their position with respect to alternative source environments influenced the composition of the communities that recruited into these ponds. These results provide further evidence of recruitment limitation in this system. Results from this study highlight the importance behaviorally limited dispersal may have in taxa morphologically capable of broad dispersal and suggest that the role of dispersal and recruitment limitation may be critical in shaping community structure across habitat gradients that include variation in habitat duration. [source] Spatial viability analysis of Amur tiger Panthera tigris altaica in the Russian Far East: the role of protected areas and landscape matrix in population persistenceJOURNAL OF APPLIED ECOLOGY, Issue 6 2006CARLOS CARROLL Summary 1The Amur or Siberian tiger Panthera tigris altaica forms a relatively small and disjunct population of less than 600 individuals in the Russian Far East. Because tigers in this region require large territories to acquire sufficient prey, current strictly protected areas, comprising 3ˇ4% (10 300 km2) of the region, are unlikely to prevent extirpation of the subspecies in the face of expanding forestry and external demand for tiger parts. 2We used resource selection function models and spatially explicit population models to analyse the distribution and predict the demographic structure of the population to identify policy options that may enhance population viability. 3A resource selection function model developed from track distribution data predicted that tigers were most likely to occur in lower altitude valley bottoms with Korean pine forest and low human impacts. 4The results from the spatially explicit population model suggested that current tiger distribution is highly dependent on de facto refugia with low human impacts but without statutory protection, and that small increases in mortality in these areas will result in range fragmentation. Although an expanded reserve network only marginally increases tiger viability under current conditions, it dramatically enhances distribution under potential future scenarios, preventing regional extirpation despite a more hostile landscape matrix. 5The portion of tiger range most resistant to extirpation connects a large coastal reserve in the central portion of the region with largely unprotected watersheds to the north. A southern block of habitat is also important but more severely threatened with anthropogenic disturbances. The results suggest that preserving source habitat in these two zones and ensuring linkages are retained between blocks of habitat in the north and south will be critical to the survival of the tiger population. 6Synthesis and applications. Conservation priorities identified in this analysis differ from those suggested by a conservation paradigm focusing only on sustaining and connecting existing protected areas that has been applied to tiger conservation in more developed landscapes with higher prey densities. An alternative paradigm that assesses population viability in a whole-landscape context and develops priorities for both protected area expansion and increasing survival rates in the landscape matrix may be more appropriate in areas where tigers and other large carnivores coexist with low-density human populations. Although landscape connectivity merits increased emphasis in conservation planning, identification of landscape linkages should be tied to broad-scale recommendations resulting from spatial viability analyses in order to prevent misdirection of resources towards protecting corridors that add little to population persistence. [source] An empirical test of source,sink dynamics induced by huntingJOURNAL OF APPLIED ECOLOGY, Issue 5 2005ANDRÉS J. NOVARO Summary 1Under the source,sink model, persistence of populations in habitat sinks, where deaths outnumber births, depends on dispersal from high-quality habitat sources, where births outnumber deaths. The persistence of the regional population depends on the proportion of sink relative to source habitat. 2Hunting that occurs in some parts of the landscape and not in others can create patches where deaths outnumber births. We tested whether hunting of culpeo foxes Pseudalopex culpaeus, which is patchily distributed in relatively homogeneous habitat in Argentine Patagonia, induces source,sink dynamics. 3On Patagonian sheep ranches, culpeos are hunted for fur and to protect sheep, and on cattle ranches hunting is usually banned. We monitored culpeo densities using scent stations and estimated survival, fecundity and dispersal by radio-tracking 44 culpeos and analysing carcasses collected from hunters on two cattle and four sheep ranches between 1989 and 1997. 4Survival of juvenile culpeos was lower on hunted than unhunted ranches, mainly as a result of hunting mortality. Reproduction could not compensate for high mortality on hunted ranches. Interruption of hunting led to an increase in juvenile survival, indicating that hunting and natural mortality were not compensatory. We concluded that sheep ranches were sinks because of the high mortality and that sink populations may be maintained by dispersal from cattle ranches. 5We used a simulation model to assess implications of changes in the proportion of source and sink areas on population dynamics. The percentage of land on cattle ranches in the study area was 37%. Current hunting pressure on culpeos would not be sustainable if that percentage fell below 30%. 6Synthesis and applications. Source,sink dynamics may occur in landscapes where hunting is intense and spatially heterogeneous. Wildlife management traditionally monitors demographic rates to evaluate the sustainability of hunting, but our results suggest that the size and spatial arrangement of areas with and without hunting should be considered as well. In regions where enforcement and monitoring are limited, securing large and regularly distributed source areas for hunted species may be more effective than trying to regulate harvest size. [source] | ||||||||||