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Species' Ecology (species + ecology)
Selected AbstractsA model for range expansion of an introduced species: the common waxbill Estrilda astrild in PortugalDIVERSITY AND DISTRIBUTIONS, Issue 6 2002Tiago Silva Abstract. The common waxbill Estrilda astrild was first introduced to Portugal from Africa in 1964, and has spread across much of the country and into Spain. We modelled the expansion of the common waxbill on a 20 × 20 km UTM grid in 4-year periods from 1964 to 1999. The time variation of the square root of the occupied area shows that this expansion process is stabilizing in Portugal, and reasons for this are discussed. Several methods used to model biological expansions are not appropriate for the present case, because little quantitative data are available on the species ecology and because this expansion has been spatially heterogeneous. Instead, colonization on a grid was modelled as a function of several biophysical and spatio-temporal variables through the fitting of a multivariate autologistic equation. This approach allows examination of the underlying factors affecting the colonization process. In the case of the common waxbill it was associated positively with its occurrence in adjacent cells, and affected negatively by altitude and higher levels of solar radiation. [source] Do changes in climate patterns in wintering areas affect the timing of the spring arrival of trans-Saharan migrant birds?GLOBAL CHANGE BIOLOGY, Issue 1 2005Oscar Gordo Abstract The life cycles of plants and animals are changing around the world in line with the predictions originated from hypotheses concerning the impact of global warming and climate change on biological systems. Commonly, the search for ecological mechanisms behind the observed changes in bird phenology has focused on the analysis of climatic patterns from the species breeding grounds. However, the ecology of bird migration suggests that the spring arrival of long-distance migrants (such as trans-Saharan birds) is more likely to be influenced by climate conditions in wintering areas given their direct impact on the onset of migration and its progression. We tested this hypothesis by analysing the first arrival dates (FADs) of six trans-Saharan migrants (cuckoo Cuculus canorus, swift Apus apus, hoopoe Upupa epops, swallow Hirundo rustica, house martin Delichon urbica and nightingale Luscinia megarhynchos), in a western Mediterranean area since from 1952 to 2003. By means of multiple regression analyses, FADs were analysed in relation to the monthly temperature and precipitation patterns of five African climatic regions south of the Sahara where species are thought to overwinter and from the European site from where FADs were collected. We obtained significant models for five species explaining 9,41% of the variation in FADs. The interpretation of the models suggests that: (1) The climate in wintering quarters, especially the precipitation, has a stronger influence on FADs than that in the species' potential European breeding grounds. (2) The accumulative effects of climate patterns prior to migration onset may be of considerable importance since those climate variables that served to summarize climate patterns 12 months prior to the onset of migration were selected by final models. (3) Temperature and precipitation in African regions are likely to affect departure decision in the species studied through their indirect effects on food availability and the build-up of reserves for migration. Our results concerning the factors that affect the arrival times of trans-Saharan migrants indicate that the effects of climate change are more complex than previously suggested, and that these effects might have an interacting impact on species ecology, for example by reversing ecological pressures during species' life cycles. [source] Modelling species distribution at multiple spatial scales: gibbon habitat preferences in a fragmented landscapeANIMAL CONSERVATION, Issue 3 2010T. N. E. Gray Abstract Conservation of Indochinese primates is hampered by a lack of knowledge of species ecology, habitat preferences and, locally, distribution. Predictive distribution and habitat suitability models, using predictors known to affect the distribution of similar species elsewhere, may, therefore be of great benefit to conservationists within the region. Yellow-cheeked crested gibbon Nomascus gabriellae is an IUCN-listed endangered primate distributed east of the Mekong River in Cambodia, southern Vietnam, and possibly southern Lao PDR. Within Cambodia, yellow-cheeked crested gibbon are naturally restricted to evergreen forest fragments within a landscape matrix of deciduous dipterocarp and semi-evergreen forests. During the 2008 dry season, auditory surveys for yellow-cheeked crested gibbon were conducted within Phnom Prich Wildlife Sanctuary, Mondulkiri province, Cambodia. Predictive distribution models, in which variables were included at the scale at which they best explained gibbon occurrence (multi-grain models), were constructed to examine the species' habitat associations and tolerance of habitat fragmentation within the wildlife sanctuary. Gibbon occupancy (,) was higher in evergreen (0.43±0.26,0.62) than in semi-evergreen forest (0.21±0.09,0.4), with gibbon presence constrained by a critical amount of evergreen forest within 5 km radius of listening posts. Three patches of optimal habitat within Phnom Prich Wildlife Sanctuary were identified. These, and connecting habitats, should be the target of increased enforcement effort to limit hunting and habitat conversion. Similar multi-grain models are likely to be valuable for conservationists within mosaic habitats as they can facilitate identification of the minimum suitable fragment size for species of conservation concern. [source] Using multi-scale species distribution data to infer drivers of biological invasion in riparian wetlandsDIVERSITY AND DISTRIBUTIONS, Issue 1 2010Jane A. Catford Abstract Aim, Biological invasion is a major conservation problem that is of interest to ecological science. Understanding mechanisms of invasion is a high priority, heightened by the management imperative of acting quickly after species introduction. While information about invading species' ecology is often unavailable, species distribution data can be collected near the onset of invasion. By examining distribution patterns of exotic and native plant species at multiple spatial scales, we aim to identify the scale (of those studied) that accounts for most variability in exotic species abundance, and infer likely drivers of invasion. Location, River Murray wetlands, south-eastern Australia. Methods, A nested, crossed survey design was used to determine the extent of variation in wetland plant abundance, grazing intensity and water depth at four spatial scales (reaches, wetland clumps, wetlands, wetland sections), and among three Depth-strata. We examined responses of exotic and native species groups (grouped into terrestrial and amphibious taxa), native weeds and 10 individual species using hierarchical ANOVA. Results, As a group dominated by terrestrial taxa, exotic species cover varied at reach-, wetland- and section-scales. This likely reflects differences in abiotic characteristics and propagule pressure at these scales. Groups based on native species did not vary at any scale examined. Cover of 10 species mostly varied among and within wetlands (patterns unrelated to species' origin or functional group), but species' responses differed, despite individual plants being similar in size. While flora mostly varied among wetlands, exotic cover varied most among reaches (26%), which was attributed to hydrological modification and human activities. Main conclusions, Multi-scale surveys can rapidly identify factors likely to affect species' distributions and can indicate where future research should be directed. By highlighting disproportionate variation in exotic cover among reaches, this study suggests that flow regulation and human-mediated dispersal facilitate exotic plant invasion in River Murray wetlands. [source] Effects of species' ecology on the accuracy of distribution modelsECOGRAPHY, Issue 1 2007Jana M. McPherson In the face of accelerating biodiversity loss and limited data, species distribution models , which statistically capture and predict species' occurrences based on environmental correlates , are increasingly used to inform conservation strategies. Additionally, distribution models and their fit provide insights on the broad-scale environmental niche of species. To investigate whether the performance of such models varies with species' ecological characteristics, we examined distribution models for 1329 bird species in southern and eastern Africa. The models were constructed at two spatial resolutions with both logistic and autologistic regression. Satellite-derived environmental indices served as predictors, and model accuracy was assessed with three metrics: sensitivity, specificity and the area under the curve (AUC) of receiver operating characteristics plots. We then determined the relationship between each measure of accuracy and ten ecological species characteristics using generalised linear models. Among the ecological traits tested, species' range size, migratory status, affinity for wetlands and endemism proved most influential on the performance of distribution models. The number of habitat types frequented (habitat tolerance), trophic rank, body mass, preferred habitat structure and association with sub-resolution habitats also showed some effect. In contrast, conservation status made no significant impact. These findings did not differ from one spatial resolution to the next. Our analyses thus provide conservation scientists and resource managers with a rule of thumb that helps distinguish, on the basis of ecological traits, between species whose occurrence is reliably or less reliably predicted by distribution models. Reasonably accurate distribution models should, however, be attainable for most species, because the influence ecological traits bore on model performance was only limited. These results suggest that none of the ecological traits tested provides an obvious correlate for environmental niche breadth or intra-specific niche differentiation. [source] Diet and food preferences of the endangered Bearded Vulture Gypaetus barbatus: a basis for their conservationIBIS, Issue 2 2009ANTONI MARGALIDA The Bearded Vulture Gypaetus barbatus population in the Pyrenees is managed using feeding stations to increase breeding success and reduce mortality in the pre-adult population. Nevertheless, very little quantitative and qualitative information has been published on such basic aspects of the species' ecology as feeding habits and dietary preferences. This study investigated both aspects through direct and unbiased observation of breeding Bearded Vultures during the chick-rearing period. Bearded Vulture diet comprises mammals (93%), birds (6%) and reptiles (1%), with medium-sized ungulates (mainly sheep/goats) the most important species in the diet (61%, n = 677). Prey items were not selected in proportion to their availability, with the remains of larger species (cows and horses) being avoided, probably due to the variable cost/benefit ratios in handling efficiency, ingestion process and transport. There is no relationship between the proportion of sheep limbs in the diet and the proximity of feeding stations, suggesting that these sites are probably less important for breeding adults than for the pre-adult population. On the other hand, diet specificity seems related to productivity, with territories with greater trophic breadth being those with higher fecundity. Bearded Vultures prefer to eat limbs, although meat remains (provided principally by small mammals) can play an important role in guaranteeing breeding success during the first few weeks after hatching. The management of carrion provided by animals that die naturally in extensive livestock practices and the remains of wild ungulates which have died naturally or by human hunting, are important conservation tools for the Bearded Vulture and other carrion-eating species. [source] Afrothismiagabonensis sp. nov. (Burmanniaceae) from GabonNORDIC JOURNAL OF BOTANY, Issue 5-6 2007G. Dauby A new species Afrothismia gabonensis Dauby & Stévart (Burmanniaceae) is described from the Pongara National Park (Gabon). It is the second Afrothismia species recorded from this country and the twelfth of the genus. The new species mainly differs from Afrothismia winkleri by its dorsal tepals which are much longer. Information on the species' ecology, phenology and distribution is provided. [source] | ||||||||||