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  • 1
    Electronic Resource
    Electronic Resource
    Fire regimes of World Heritage Kakadu National Park., Australia (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Austral ecology 25 (2000), S. 0 
    Details
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract LANDSAT Multi-Spectral Scanner imagery was used to determine aspects of the fire regimes of Kakadu National Park (in the wet-dry tropics of Australia) for the period 1980–1995. Three landscape types recognized in this Park were Plateau, Lowlands and Floodplain. Areas burned in early and late dry seasons each year were documented using a Geographical Information System. Regression analyses were used to examine time trends in the areas burned each year and the interrelationships between early and late dry season burning. The proportions of landscapes having different stand ages (years since fire), and the proportions having had different fire intervals, were compared with results expected from the simplest random model (i.e. one in which the probability of ignition at a point [PIP] burning annually was constant). Using overlays of successive stand-age maps, PIP could be calculated as a function of stand age. The Lowlands burned extensively each year; the areas burned by late dry season fires adding to those burned in the early dry season such that around 50–60% of the total area burned annually. Early dry season fires have lower intensities than late dry season fires, on average. Using a theoretically constant PIP and the mean proportion burned per year as the only input, predictions of areas burned as a function of stand age and fire interval were reasonable when compared with the empirical data, but best for the Lowlands landscape. PIP functions for Lowlands and Floodplains had negative slopes, an unexpected result. The nature of these PIP functions may reflect heterogeneity in fire proneness of the various vegetation types within landscapes. The scale of measurement, the scale of variation in vegetation types within a landscape, and the accuracy of the determination of burned areas, are constraints on the accuracy of fire-interval and seasonally determination perceived from an analysis of satellite data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1442-9993.2000.tb00067.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of physical factors and ornithogenic products on plant and arthropod abundance at an Inland Nunatak group in Antarctica (1989)
    Springer
    Polar biology 10 (1989), S. 151-160 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Robertskollen is a group of geologically similar nunataks in western Dronning Maud Land, Antarctica, with breeding colonies of snow petrels Pagodroma nivea at some of the nunataks. Transects determining macro-plant structure and cover were conducted along an a priori determined bird-influence gradient to assess the relative importance of ornithogenic products and physical factors on plant assemblages. Fine-scale (intra-transect) dispersion patterns of plants were determined primarily by physical factors affecting water availability (i.e. the amount of drift-snow available and the effects of shelter and shade on evaporation rates). Coarse-scale (inter-transect) analysis of plant dispersion patterns, however, showed significant responses along the bird-influence gradient, with consistent responses between nunataks. Plant cover was directly related to bird-influence, but was depressed within bird colonies, apparently due to excessive nutrient enrichment. Mites (Acari) were the only arthropods recorded at Robertskollen and total mite abundance was related to plant cover, although specific responses varied. Thallus diameters of the abundant lichen Umbilicaria decussata decreased with decreasing bird influence, suggesting that nutrients limit plant growth away from bird colonies. Soil concentrations of major plant nutrients, N, P and K, were significantly greater close to bird colonies. We conclude that nutrients in ornithogenic products have direct causal effects on the abundance and dispersion of the biota of inland Antarctic nunataks, and that the effects of nutrient enrichment are detectable at different spatial scales from the effects of physical factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239162
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The distribution and abundance of aerial seabirds in relation to Antarctic krill in the Prydz Bay region, Antarctica, during late summer (1989)
    Springer
    Polar biology 10 (1989), S. 199-209 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The distribution patterns of aerial seabirds are analysed from counts made in the Prydz Bay region, Antarctica, during the African legs of SIBEX I and II in late summer (end of February to April), and compared with those made farther west at the same time of year during FIBEX. Species composition and abundances were similar in all three surveys, with sooty shearwaters Puffinus griseus contributing approximately half of the total aerial bird energy demand. Differences between surveys are explained in terms of longitudinal or seasonal differences in sampling areas and periods. Correlations between bird distribution patterns and environmental parameters are used to infer the scale-dependent factors affecting bird dispersion at sea. Two macro-scale bird assemblages, identified by physical parameters, were separated along latitudinal gradients (temperature and salinity) associated with the Antarctic Divergence. These assemblages are consistent with the Intermediate and Southern High Latitude Groups identified during FIBEX. At smaller spatial scales, almost all species were correlated with the abundance of Antarctic krill Euphausia superba, both across the entire SIBEX I grid, and within the areas north and south of the Antarctic Divergence. Similarly, during SIBEX II, seabird densities were six times greater when krill was abundant than when krill was scarce. Sooty shearwaters, which appeared to be moving through the area, were the only abundant bird species not correlated with krill abundance. Possible reasons why previous studies have not detected correlations between seabird and krill abundances are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238496
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  • 4
    Electronic Resource
    Electronic Resource
    Intraspecific mimicry and status signals in juvenile African penguins (1987)
    Springer
    Behavioral ecology and sociobiology 20 (1987), S. 69-76 
    Details
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Observations of resting groups of African penguins Spheniscus demersus on land showed that adults were more aggressive towards juveniles than towards adults. Head coloration was important in triggering this aggression. Adults probably discriminate against juveniles to exclude inexperienced birds from co-operative feeding groups and thus maximize their own energetic returns. There was a disproportionately low frequency of penguin groups at sea containing both adult and juvenile birds. Almost a quarter of juvenile penguins moulted a variable amount of their heads into adult plumage at sea. This reduced the amount of aggression received in proportion to the degree of head moult. Head moult probably occurs in only the fittest juveniles. Birds which moult can join adult feeding groups where communal feeding enhances success. The costs of moulting at sea prevent the occurrence of head moulting in the entire population of juveniles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292167
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  • 5
    Electronic Resource
    Electronic Resource
    The role of disturbance in the establishment of indigenous and alien plants at Inaccessible and Nightingale Islands in the South Atlantic Ocean (1994)
    Springer
    Plant ecology 113 (1994), S. 13-23 
    Details
    ISSN: 1573-5052
    Keywords: Albatross ; Alien-plants ; Disturbances ; Seedling ; Soil-slip ; South Atlantic Islands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Disturbances play an important role in the establishment of vegetation at Inaccessible and Nightingale Islands in the South Atlantic Ocean. Type, altitude and age of disturbance all influenced the species richness, life-form and abundance of seedlings. A few indigenous species appear to be dependent on small disturbances, such as the clearings around albatross nests, for their perpetuation, e.g. Acaena sarmentosa and Gnaphalium thouarsii. Alien forbs and grasses, e.g. Conyza albida, Holcus lanatus, Pseudognaphalium luteo-album and Rumex obtusifolius, tended to dominate large recent disturbances such as soil-slips and depressions, and to colonize man-modified sites. Alien plants were less common on the plateau at Inaccessible Island than on the lowlands. Their success appears to be enhanced by large-scale disturbances. The highest density and diversity of seedlings occurred on large soil-slips where mineral soil was exposed and vegetation cover was minimal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045460
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  • 6
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    Exploitation of mesoscale oceanographic features by grey-headed albatross Thalassarche chrysostoma in the southern Indian Ocean (2001)
    InterResearch
    In:  Marine Ecology Progress Series, 217 . pp. 15-26.
    Details
    Publication Date: 2021-06-28
    Description: Breeding grey-headed albatross Thalassarche chrysostoma, tracked from Marion Island (Prince Edward Islands) during November-December 1997 and January-February 1998, showed a strong association with mesoscale oceanographic features, as identified by sea surface height anomalies, in the southern Indian Ocean. During incubation, most birds foraged to the north of the island, at the edges of anomalies created by the Agulhas Return Current in the Subtropical Convergence and the Subantarctic zones. In contrast, during chick-rearing all tracked birds foraged to the southwest of the island, at the edges of anomalies along the South-West Indian Ridge. Previous work in this area has shown that these anomalies are in fact eddies that are created as the Antarctic Circumpolar Current crosses the South-West Indian Ridge. Diet samples taken during the chick-rearing period showed a predominance of fresh specimens of the predatory fish Magnisudis prionosa and the squid Martialia hyadesi. Myctophid fish and amphipods Themisto gaudichaudii, both known prey of M. hyadesi, were also well represented in our samples. Diet samples taken from tracked birds showed birds feeding at edges of positive anomalies returning with fresh specimens of M. prionosa and M. hyadesi. Predatory fish and squid are thus presumably concentrated at these features. Eddies formed at the South-West Indian Ridge have also been shown to drift closer to Marion Island, within the foraging range of penguins and seals breeding on Marion Island. We therefore suggest that these mesoscale oceanographic features may be an important component of the Œlife-support¹ system enabling globally significant populations of seabirds and seals to breed at the Prince Edward Islands.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps217015
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Foraging interactions of wandering albatrosses Diomedea exulans breeding on Marion Island with longline fisheries in the southern Indian Ocean: Seasonal and gender effects (2002)
    Wiley
    In:  Ibis, 144 (3). E141-E154.
    Details
    Publication Date: 2017-01-30
    Description: Wandering Albatrosses Diomedea exulans are frequently killed when they attempt to scavenge baited hooks deployed by long-line fishing vessels. We studied the foraging ecology of Wandering Albatrosses breeding on Marion Island in order to assess the scale of interactions with known long-line fishing fleets. During incubation and late chick-rearing, birds foraged further away from the island, in warmer waters, and showed high spatial overlap with areas of intense tuna Thunnus spp. long-line fishing. During early chick-rearing, birds made shorter foraging trips and showed higher spatial overlap with the local Patagonian Toothfish Dissostichus eleginoides long-line fishery. Tracks of birds returning with offal from the Toothfish fishery showed a strong association with positions at which Toothfish long-lines were set and most diet samples taken during this stage contained fishery-related items. Independent of these seasonal differences, females foraged further from the islands and in warmer waters than males. Consequently, female distribution overlapped more with tuna long-line fisheries, whereas males interacted more with the Toothfish long-line fishery. These factors could lead to differences in the survival probabilities of males and females. Non-breeding birds foraged in warmer waters and showed the highest spatial overlap with tuna long-line fishing areas. The foraging distribution of Marion Island birds showed most spatial overlap with birds from the neighbouring Crozet Islands during the late chick-rearing and non-breeding periods. These areas of foraging overlap also coincided with areas of intense tuna long-line fishing south of Africa. As the population trends of Wandering Albatrosses at these two localities are very similar, it is possible that incidental mortality during the periods when these two populations show the highest spatial overlap could be driving these trends.
    Type: Article , PeerReviewed
    DOI: 10.1046/j.1474-919X.2002.00092.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Genetics of Rapid and Extreme Size Evolution in Island Mice [Population and Evolutionary Genetics] (2015)
    Genetics Society of America (GSA)
    In: Genetics
    Details
    Publication Date: 2015-09-10
    Description: Organisms on islands provide a revealing window into the process of adaptation. Populations that colonize islands often evolve substantial differences in body size from their mainland relatives. Although the ecological drivers of this phenomenon have received considerable attention, its genetic basis remains poorly understood. We use house mice (subspecies: Mus musculus domesticus ) from remote Gough Island to provide a genetic portrait of rapid and extreme size evolution. In just a few hundred generations, Gough Island mice evolved the largest body size among wild house mice from around the world. Through comparisons with a smaller-bodied wild-derived strain from the same subspecies (WSB/EiJ), we demonstrate that Gough Island mice achieve their exceptional body weight primarily by growing faster during the 6 weeks after birth. We use genetic mapping in large F 2 intercrosses between Gough Island mice and WSB/EiJ to identify 19 quantitative trait loci (QTL) responsible for the evolution of 16-week weight trajectories: 8 QTL for body weight and 11 QTL for growth rate. QTL exhibit modest effects that are mostly additive. We conclude that body size evolution on islands can be genetically complex, even when substantial size changes occur rapidly. In comparisons to published studies of laboratory strains of mice that were artificially selected for divergent body sizes, we discover that the overall genetic profile of size evolution in nature and in the laboratory is similar, but many contributing loci are distinct. Our results underscore the power of genetically characterizing the entire growth trajectory in wild populations and lay the foundation necessary for identifying the mutations responsible for extreme body size evolution in nature.
    Print ISSN: 0016-6731
    Topics: Biology
    Published by Genetics Society of America (GSA)
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  • 9
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    Comment on "Marine plastic debris emits a keystone infochemical for olfactory foraging seabirds" by Savoca et al. (2017)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2017-06-29
    Description: In their recent paper, Savoca and collaborators (2016) showed that plastic debris in the ocean may acquire a dimethyl sulfide (DMS) signature from biofouling developing on their surface. According to them, DMS emission may represent an olfactory trap for foraging seabirds, which explains patterns of plastic ingestion among procellariiform seabirds. This hypothesis is appealing, but some of the data that Savoca et al. used to support their claim are questionable, resulting in a misclassification of species, as well as other decisions regarding the variables to include in their models. Furthermore, with their focus on a single lifestyle trait (nesting habit) of dubious relevance for explaining plastic ingestion, Savoca et al. neglect the opportunity to explore other factors that might provide better ecological insight. Finally, we are deeply concerned by the conservation policy recommendation proposed by Savoca et al. —to increase antifouling properties of consumer plastics—which constitutes a substantial environmental risk and delivers the wrong message to decision-makers. The reduction of plastic consumption, waste prevention, and proactive reuse through a circular economy should be at the heart of policy recommendations for future mitigation efforts.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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