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Large Islands (large + island)
Selected AbstractsAdaptive Units for Conservation: Population Distinction and Historic Extinctions in the Island Scrub-JayCONSERVATION BIOLOGY, Issue 2 2005KATHLEEN S. DELANEY Aphelocoma; diversidad genética especie; endémica; genética de conservación; Islas Channel Abstract:,The Island Scrub-Jay (Aphelocoma insularis) is found on Santa Cruz Island, California, and is the only insular bird species in the continental United States. We typed seven microsatellite loci and sequenced a portion of the mitochondrial DNA control region of Island Scrub-Jays and their closest mainland relative, the Western Scrub-Jay (Aphelocoma californica), to assess levels of variability and effective population size and to examine the evolutionary relationship between the two species. The estimated female effective population size, Nef, of the Island Scrub-Jay was 1603 (90% confidence interval: 1481,1738) and was about 7.5% of the size of the mainland species. Island and Western Scrub-Jays have highly divergent control-region sequences, and the value of 3.14 ± 0.09% sequence divergence between the two species suggests a divergence time of approximately 151,000 years ago. Because the four northern Channel Islands were joined as one large island as recently as 11,000 years ago, extinctions must have occurred on the three other northern Channel islands, Santa Rosa, San Miguel, and Anacapa, highlighting the vulnerability of the remaining population. We assessed the evolutionary significance of four island endemics, including the Island Scrub-Jay, based on both genetic and adaptive divergence. Our results show that the Island Scrub-Jay is a distinct species of high conservation value whose history and adaptive potential is not well predicted by study of other island vertebrates. Resumen:, Aphelocoma insularis se encuentra en la Isla Santa Cruz, California, y es la única especie de ave insular en Estados Unidos continental. Clasificamos siete locus microsatelitales y secuenciamos una porción de la región control del ADN mitocondrial de A. insularis y su pariente continental más cercano A. californica para evaluar niveles de variabilidad y tamańo poblacional efectivo y examinar las relaciones evolutivas entre las dos especies. El tamańo poblacional efectivo de hembras, Neh, de A. insularis fue estimado en 1603 (90% CI: 1481-1738) y fue aproximadamente 7.5% del tamańo de la especie continental. Aphelocoma insularis y A. californica tienen secuencias muy divergentes en la región control, y el valor de divergencia secuencial de 3.14 ± 0.09% entre las dos especies sugiere un tiempo de divergencia de aproximadamente 151,000 ańos. Debido a que las cuatro Islas Channel estuvieron unidas en una sola isla tan recientemente como hace 11,000 ańos, deben haber ocurrido extinciones en las otras tres islas Channel, Santa Rosa, San Miguel y Anacapa, acentuando la vulnerabilidad de la población remanente. Evaluamos el significado evolutivo de cuatro especies insulares endémicas incluyendo A. insularis con base en la divergencia genética y adaptativa. Nuestros resultados muestran que A. insularis es una especie distinta de alto valor de conservación, cuya historia y potencial adaptativo no es pronosticado correctamente por el estudio de otros vertebrados insulares. [source] Estimating natal dispersal movement rates of female European ducks with multistate modellingJOURNAL OF ANIMAL ECOLOGY, Issue 6 2003Peter Blums Summary 1We used up to 34 years of capture,recapture data from about 22 100 new releases of day-old female ducklings and multistate modelling to test predictions about the influence of environmental, habitat and management factors on natal dispersal probability of three species of ducks within the Engure Marsh, Latvia. 2The mean natal dispersal distances were very similar (c. 0·6,0·7 km) for all three species and were on average 2·7 times greater than breeding dispersal distances recorded within the same study system. 3We were unable to confirm the kinship hypothesis and found no evidence that young first-nesting females nested closer to their relatives (either mother or sister) than to the natal nest. 4Young female northern shovelers, like adults, moved from small islands to the large island when water level was high and vice versa when water level was low before the construction of elevated small islands. Movement probabilities between the two strata were much higher for young shovelers than adults, suggesting that young birds had not yet developed strong fidelity to the natal site. Movements of young female tufted ducks, unlike those of shovelers, were not dependent on water level fluctuations and reflected substantial flexibility in choice of first nesting sites. 5Data for young birds supported our earlier conclusion that common pochard nesting habitats in black-headed gull colonies were saturated during the entire study period. Young females, like the two adult age groups, moved into and out of colonies with similar probability. Fidelity probability of female pochards to each stratum increased with age, being the lowest (0·62) for young (DK) females, intermediate (0·78) for yearlings (SY) and the highest (0·84) for adult (ASY) females. 6Young female tufted ducks, like adults, showed higher probabilities of moving from islands to emergent marshes when water levels were higher both before and after habitat management. The relationship between the spring water levels and movement was much weaker for young females than for adults. 7Young female diving ducks exhibited much stronger (compared to adults) asymmetric movement with respect to proximity to water, with higher movement probabilities to near-water locations than away from these locations. 8Local survival of day-old ducklings during the first year of life was time-specific and very low (means for different strata/states 0·01,0·08) because of high rates of emigration and prefledging mortality. [source] Phylogeography of the world's tallest angiosperm, Eucalyptus regnans: evidence for multiple isolated Quaternary refugiaJOURNAL OF BIOGEOGRAPHY, Issue 1 2010Paul G. Nevill Abstract Aim, There is a need for more Southern Hemisphere phylogeography studies, particularly in Australia, where, unlike much of Europe and North America, ice sheet cover was not extensive during the Last Glacial Maximum (LGM). This study examines the phylogeography of the south-east Australian montane tree species Eucalyptus regnans. The work aimed to identify any major evolutionary divergences or disjunctions across the species' range and to examine genetic signatures of past range contraction and expansion events. Location, South-eastern mainland Australia and the large island of Tasmania. Methods, We determined the chloroplast DNA haplotypes of 410 E. regnans individuals (41 locations) based on five chloroplast microsatellites. Genetic structure was examined using analysis of molecular variance (AMOVA), and a statistical parsimony tree was constructed showing the number of nucleotide differences between haplotypes. Geographic structure in population genetic diversity was examined with the calculation of diversity parameters for the mainland and Tasmania, and for 10 regions. Regional analysis was conducted to test hypotheses that some areas within the species' current distribution were refugia during the LGM and that other areas have been recolonized by E. regnans since the LGM. Results, Among the 410 E. regnans individuals analysed, 31 haplotypes were identified. The statistical parsimony tree shows that haplotypes divided into two distinct groups corresponding to mainland Australia and Tasmania. The distribution of haplotypes across the range of E. regnans shows strong geographic patterns, with many populations and even certain regions in which a particular haplotype is fixed. Many locations had unique haplotypes, particularly those in East Gippsland in south-eastern mainland Australia, north-eastern Tasmania and south-eastern Tasmania. Higher haplotype diversity was found in putative refugia, and lower haplotype diversity in areas likely to have been recolonized since the LGM. Main conclusions, The data are consistent with the long-term persistence of E. regnans in many regions and the recent recolonization of other regions, such as the Central Highlands of south-eastern mainland Australia. This suggests that, in spite of the narrow ecological tolerances of the species and the harsh environmental conditions during the LGM, E. regnans was able to persist locally or contracted to many near-coastal refugia, maintaining a diverse genetic structure. [source] Patterns of species richness on very small islands: the plants of the Aegean archipelagoJOURNAL OF BIOGEOGRAPHY, Issue 7 2006Maria Panitsa Abstract Aim, To investigate the species,area relationship (SAR) of plants on very small islands, to examine the effect of other factors on species richness, and to check for a possible Small Island Effect (SIE). Location, The study used data on the floral composition of 86 very small islands (all < 0.050 km2) of the Aegean archipelago (Greece). Methods, We used standard techniques for linear and nonlinear regression in order to check several models of the SAR, and stepwise multiple regression to check for the effects of factors other than area on species richness (,habitat diversity', elevation, and distance from nearest large island), as well as the performance of the Choros model. We also checked for the SAR of certain taxonomic and ecological plant groups that are of special importance in eastern Mediterranean islands, such as halophytes, therophytes, Leguminosae and Gramineae. We used one-way anova to check for differences in richness between grazed and non-grazed islands, and we explored possible effects of nesting seabirds on the islands' flora. Results, Area explained a small percentage of total species richness variance in all cases. The linearized power model of the SAR provided the best fit for the total species list and several subgroups of species, while the semi-log model provided better fits for grazed islands, grasses and therophytes. None of the nonlinear models explained more variance. The slope of the SAR was very high, mainly due to the contribution of non-grazed islands. No significant SIE could be detected. The Choros model explained more variance than all SARs, although a large amount of variance of species richness still remained unexplained. Elevation was found to be the only important factor, other than area, to influence species richness. Habitat diversity did not seem important, although there were serious methodological problems in properly defining it, especially for plants. Grazing was an important factor influencing the flora of small islands. Grazed islands were richer than non-grazed, but the response of their species richness to area was particularly low, indicating decreased floral heterogeneity among islands. We did not detect any important effects of the presence of nesting seabird colonies. Main conclusions, Species richness on small islands may behave idiosyncratically, but this does not always lead to a typical SIE. Plants of Aegean islets conform to the classical Arrhenius model of the SAR, a result mainly due to the contribution of non-grazed islands. At the same time, the factors examined explain a small portion of total variance in species richness, indicating the possible contribution of other, non-standard factors, or even of stochastic effects. The proper definition of habitat diversity as pertaining to the taxon examined in each case is a recurrent problem in such studies. Nevertheless, the combined effect of area and a proxy for environmental heterogeneity is once again superior to area alone in explaining species richness. [source] THE HIGH-WATER MARK: THE SITING OF MEGALITHIC TOMBS ON THE SWEDISH ISLAND OF TJÖRNOXFORD JOURNAL OF ARCHAEOLOGY, Issue 2 2004RICHARD BRADLEY Summary. In 1977 Grahame Clark suggested that the siting of megalithic tombs along the west coast of Scandinavia reflected the distribution of productive fishing grounds. Unlike the situation in other parts of Europe, these monuments were not associated with agriculture. Opinions have varied over the last quarter century, but enough is now known about changes of sea-level for his interpretation to be investigated on the ground. There seems to have been considerable diversity. On the large island of Örust some of the tombs located near to the sea appear to be associated with small natural enclosures defined by rock outcrops and may have been associated with grazing land. On the neighbouring island of Tjörn, however, the tombs were associated with small islands and important sea channels. During the Bronze Age the same areas included carvings of ships. Recent fieldwork in western Norway suggests that such locations were especially important in a maritime economy. [source] Distributions of forest birds and butterflies in the Andaman islands, Bay of Bengal: nested patterns and processesECOGRAPHY, Issue 1 2002Priya Davidar The distributional patterns of forest birds and butterflies in the Andaman islands, an oceanic chain located off SE Asia, were tested for nestedness. Both taxa were highly nested. Nestedness could be due to colonization or extinction processes, area or distance effects or nestedness of habitats. Nestedness in forest bird distributions were strongly influenced by area and habitat related factors. Habitats were significantly nested in all three island groups, however most strongly for the North Andamans. However forest bird distributions in the North Andamans, as indicated by row order in the packed matrix, was not correlated with habitat diversity, suggesting that habitat related factors alone cannot account for these patterns. Other causal influences could be passive sampling, where common and abundant species and habitats are more likely to have a widespread distribution than rare species and habitats. The nested subset pattern seen in two unrelated taxa suggests that the Andamans are extinction dominated and that the protection of forests on large islands is critical for the conservation of its biodiversity. [source] Temporal dynamics and nestedness of an oceanic island bird faunaGLOBAL ECOLOGY, Issue 4 2006Ermias T. Azeria ABSTRACT Aim, To examine temporal variation in nestedness and whether nestedness patterns predict colonization, extinction and turnover across islands and species. Location, Dahlak Archipelago, Red Sea. Method, The distributions of land birds on 17 islands were recorded in two periods 30 years apart. Species and islands were reordered in the Nestedness Temperature Calculator, software for assessing degrees of nestedness in communities. The occupancy probability of each cell, i.e. species,island combinations, was calculated in the nested matrix and an extinction curve (boundary line) was specified. We tested whether historical and current nested ranks of species and islands were correlated, whether there was a relationship between occupancy probability (based on the historical data) and number of extinctions or colonizations (regression analyses) and whether the boundary line could predict extinctions and colonizations (chi-square analyses). Results, Historical and current nested ranks of islands and species were correlated but changes in occupancy patterns were common, particularly among bird species with intermediate incidence. Extinction and turnover of species were higher for small than large islands, and colonization was negatively related to isolation. As expected, colonizations were more frequent above than below the boundary line. Probability of extinction was highest at intermediate occupancy probability, giving a quadratic relationship between extinction and occupancy probability. Species turnover was related to the historical nested ranks of islands. Colonization was related negatively while extinction and occupancy turnover were related quadratically to historical nested ranks of species. Main conclusions, Some patterns of the temporal dynamics agreed with expectations from nested patterns. However, the accuracy of the predictions may be confounded by regional dynamics and distributions of idiosyncratic, resource-limited species. It is therefore necessary to combine nestedness analysis with adequate knowledge of the causal factors and ecology of targeted species to gain insight into the temporal dynamics of assemblages and for nestedness analyses to be helpful in conservation planning. [source] Bird species numbers in an archipelago of reeds at Lake Velence, HungaryGLOBAL ECOLOGY, Issue 6 2000András Báldi Abstract 1,Bird species numbers were studied on 109 reed islands at Lake Velence, Hungary, in the 1993 and 1994 breeding seasons. The aim was to describe and account for the abundance and distribution patterns of the bird species. 2,It was expected that an exponential model would fit the calculated species,area curves. However, for the 1993 data, both the power function (LogS ~ LogArea) and the exponential (S ~ LogArea) models did so, while the power function, exponential and linear (S ~ A) models fitted the curves for the 1994 data. 3,The results showed that the pattern was not random: a collection of small islands held more species than a few large islands with the same total area. 4,The relative species richness of small islands is a result of the preference of most common passerine bird species for the edges of reed islands. Most individuals were found in the first 5 m of the reedbed, and no edge avoidance was detected on a local spatial scale. Large, rarer species (e.g. Great White Egret), however, were found to be dependent on large reed islands. 5,Comparison of results with two other studies on bird communities of reed islands revealed that the type of landscape matrix (e.g. deep water, shallow water or agricultural lands) among reed patches significantly influences bird communities. Deep water was dominated by grebes and coot, shallow water by reed-nesting passerines, and farmed areas by reed- and bush-nesting passerines. [source] Body size,climate relationships of European spidersJOURNAL OF BIOGEOGRAPHY, Issue 3 2010Wiebke Entling Abstract Aim, Geographic body size patterns of mammals and birds can be partly understood under the framework of Bergmann's rule. Climatic influences on body size of invertebrates, however, appear highly variable and lack a comparable, generally applicable theoretical framework. We derived predictions for body size,climate relationships for spiders from the literature and tested them using three datasets of variable spatial extent and grain. Location, Europe. Methods, To distinguish climate from space, we compared clines in body size within three datasets with different degrees of co-variation between latitude and climate. These datasets were: (1) regional spider faunas from 40 European countries and large islands; (2) local spider assemblages from standardized samples in 32 habitats across Europe; and (3) local spider assemblages from Central European habitats. In the latter dataset climatic conditions were determined more by habitat type than by geographic position, and therefore this dataset provided a non-spatial gradient of various microclimates. Spider body size was studied in relation to latitude, temperature and water availability. Results, In all three datasets the mean body size of spider assemblages increased from cool/moist to warm/dry environments. This increase could be accounted for by turnover from small-bodied to large-bodied spider families. Body size,climate relationships within families were inconsistent. Main conclusions, Starvation resistance and accelerated maturation can be ruled out as explanations for the body size clines recorded, because they predict the inverse of the observed relationship between spider body size and temperature. The relationship between body size and climate was partly independent of geographic position. Thus, the restriction of large-bodied spiders to their glacial refugia owing to dispersal limitations can be excluded. Our results are consistent with mechanisms invoking metabolic rate, desiccation resistance and community interactions to predict a decrease in body size from warm and dry to cool and moist conditions. [source] Towards a more general species,area relationship: diversity on all islands, great and smallJOURNAL OF BIOGEOGRAPHY, Issue 4 2001Lomolino Aim To demonstrate a new and more general model of the species,area relationship that builds on traditional models, but includes the provision that richness may vary independently of island area on relatively small islands (the small island effect). Location We analysed species,area patterns for a broad diversity of insular biotas from aquatic and terrestrial archipelagoes. Methods We used breakpoint or piecewise regression methods by adding an additional term (the breakpoint transformation) to traditional species,area models. The resultant, more general, species,area model has three readily interpretable, biologically relevant parameters: (1) the upper limit of the small island effect (SIE), (2) an estimate of richness for relatively small islands and (3) the slope of the species,area relationship (in semi-log or log,log space) for relatively large islands. Results The SIE, albeit of varying magnitude depending on the biotas in question, appeared to be a relatively common feature of the data sets we studied. The upper limit of the SIE tended to be highest for species groups with relatively high resource requirements and low dispersal abilities, and for biotas of more isolated archipelagoes. Main conclusions The breakpoint species,area model can be used to test for the significance, and to explore patterns of variation in small island effects, and to estimate slopes of the species,area (semi-log or log,log) relationship after adjusting for SIE. Moreover, the breakpoint species,area model can be expanded to investigate three fundamentally different realms of the species,area relationship: (1) small islands where species richness varies independent of area, but with idiosyncratic differences among islands and with catastrophic events such as hurricanes, (2) islands beyond the upper limit of SIE where richness varies in a more deterministic and predictable manner with island area and associated, ecological factors and (3) islands large enough to provide the internal geographical isolation (large rivers, mountains and other barriers within islands) necessary for in situ speciation. [source] What do human economies, large islands and forest fragments reveal about the factors limiting ecosystem evolution?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2009E. G. LEIGH Abstract What factors limit ecosystem evolution? Like human economies, ecosystems are arenas where agents compete for locally limiting resources. Like economies, but unlike genes, ecosystems are not units of selection. In both economies and ecosystems, productivity, diversity of occupations or species and intensity of competition presuppose interdependence among many different agents. In both, competitive dominants need abundant, varied resources, and many agents' products or services, to support the activity and responsiveness needed to maintain dominance. Comparing different-sized land masses suggests that productivity is lower on islands whose area is too small to maintain some of the interdependences that maintain diversity, productivity and competitiveness in mainland ecosystems. Islands lacking the rare, metabolically active dominants that make competition so intense in mainland ecosystems are more easily invaded by introduced exotics. Studies of islets in reservoirs identify mechanisms generating these phenomena. These phenomena suggest how continued fragmentation will affect future ,natural' ecosystems. [source] Investigations of InSb-based quantum dots grown by molecular-beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2007N. Deguffroy Abstract InSb quantum dots (QDs) have been grown by molecular-beam epitaxy (MBE) on GaSb substrates. Typical MBE growth conditions lead to a low density (,109 cm,2) of large islands which are dislocated. Insertion of a thin InAs nucleation layer increases the QDs density by one order of magnitude which is interpreted in terms of differing In-to-group-V binding energies. Finally, we show that a high density (,7 x 1010 cm,2) of small coherent QDs can be grown by using a two-steps procedure. Photoluminescence near 3.5 µm is demonstrated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Temporal changes in the island flora at different scales in the archipelago of SW FinlandAPPLIED VEGETATION SCIENCE, Issue 4 2010Jens-Johan Hannus Abstract Question: How have species richness and vegetation patterns changed in a group of islands in the northern Baltic Sea over a 58-yr period of changing land use and increasing eutrophication? Location: A group of 116 islands, the Brunskär sub-archipelago, in SW Finland. Methods: A complete survey of vascular plant species performed in 1947,1949 by Skult was repeated by our group using the same methodology in 2005,2007 (historical versus contemporary, respectively). DCAs were performed and total number of species, extinction,colonization rates, species frequency changes and mean Ellenberg indicator values for light, moisture and nitrogen and Eklund indicator values for dependence of human cultural influence were obtained for each island and relevé. Results: Species richness has declined on large islands and increased on small islands. The increase in number of species on small islands is driven by a strong increase in frequency of shore species, which in turn is induced by more productive shores. The decrease in species richness on large islands is related to overgrowth of open semi-natural habitats after cessation of grazing and other agricultural practices. Conclusions: After the late 1940s, open habitats, which were created and maintained by cattle grazing and other traditional agricultural activities, have declined in favour of woody shrub and forest land. Shores have been stabilized and influenced by the eutrophication of the Baltic Sea, and the vegetation has become more homogeneous. This development, resulting in lower species diversity, poses a challenge for the preservation of biodiversity both on a local and on a landscape level. [source] | |||||||||||||