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Large Water Bodies (large + water_body)
Selected AbstractsEstimated migration rates under scenarios of global climate changeJOURNAL OF BIOGEOGRAPHY, Issue 7 2002Jay R. Malcolm Aim Greenhouse-induced warming and resulting shifts in climatic zones may exceed the migration capabilities of some species. We used fourteen combinations of General Circulation Models (GCMs) and Global Vegetation Models (GVMs) to investigate possible migration rates required under CO2 -doubled climatic forcing. Location Global. Methods Migration distances were calculated between grid cells of future biome type x and nearest same-biome-type cells in the current climate. In `base-case' calculations, we assumed that 2 × CO2 climate forcing would occur in 100 years, we used ten biome types and we measured migration distances as straight-line distances ignoring water barriers and human development. In sensitivity analyses, we investigated different time periods of 2 × CO2 climate forcing, more narrowly defined biomes and barriers because of water bodies and human development. Results In the base-case calculations, average migration rates varied significantly according to the GVM used (BIOME3 vs. MAPSS), the age of the GCM (older- vs. newer-generation GCMs), and whether or not GCMs included sulphate cooling or CO2 fertilization effects. However, high migration rates (, 1000 m year,1) were relatively common in all models, consisting on average of 17% grid cells for BIOME3 and 21% for MAPSS. Migration rates were much higher in boreal and temperate biomes than in tropical biomes. Doubling of the time period of 2 × CO2 forcing reduced these areas of high migration rates to c. 12% of grid cells for both BIOME3 and MAPSS. However, to obtain migration rates in the Boreal biome that were similar in magnitude to those observed for spruce when it followed the retreating North American Glacier, a radical increase in the period of warming was required, from 100 to >1000 years. A reduction in biome area by an order of magnitude increased migration rates by one to three orders of magnitude, depending on the GVM. Large water bodies and human development had regionally important effects in increasing migration rates. Main conclusions In conclusion, evidence from coupled GCMs and GVMs suggests that global warming may require migration rates much faster than those observed during post-glacial times and hence has the potential to reduce biodiversity by selecting for highly mobile and opportunistic species. Several poorly understood factors that are expected to influence the magnitude of any such reduction are discussed, including intrinsic migrational capabilities, barriers to migration, the role of outlier populations in increasing migration rates, the role of climate in setting range limits and variation in species range sizes. [source] Spatio-temporal shifts in gradients of habitat quality for an opportunistic avian predatorECOGRAPHY, Issue 2 2003Fabrizio Sergio We used the conceptual framework of the theory of natural selection to study breeding habitat preferences by an opportunistic avian predator, the black kite Milvus migrans. In Europe, black kite populations are mostly found near large networks of aquatic habitats, usually considered optimal for foraging and breeding. We hypothesized that proximity to wetlands could vary among individuals and affect their fitness, and thus be subject to natural selection. We tested the hypothesis first on a population on Lake Lugano (Italian pre-Alps) which has been monitored for nine years, and then on seven other populations, each studied for four,five years, located along a continuum of habitat from large water bodies to scarce aquatic habitat of any kind. In the Lake Lugano population, black kite abundance was negatively related to distance to the lake in all the nine years of study, consistent with long-term natural selection. There was evidence of ongoing directional selection on strategic nest location in three of the years, and evidence of stabilizing selection in two years. In eight of the nine years the trend was for a linear increase in fitness with increasing proximity to the lake. At the population level, results were consistent with adaptive habitat choice in relation to the previous year's spatial variation in fitness: higher associations between fitness and distance to the lake (i.e. higher selection gradients) resulted in higher density variations in the following year, in turn related to the availability of fish, the main local prey. The progressive decline of inland pairs and increase in the density of lakeshore pairs caused a directional long-term trend of declining mean distance to the lake. Breeding near aquatic habitats was associated with higher foraging success, and higher frequency and biomass of prey deliveries to offspring. There was weak evidence of selection in other populations. The inland-wetland gradient of habitat quality may have been affected by predation risk, as estimated by density of a major predator of adults and nestlings, the eagle owl Bubo bubo. Behavioral decisions at the level of the individual probably translated into population effects on density and distribution at various spatial scales. Populations in optimal habitats showed higher density and produced six times as many young per unit space as those in sub-optimal habitats. [source] The Branchiopoda (Crustacea: Anomopoda, Ctenopoda and Cyclestherida) of the rain forests of Cameroon, West Africa: low abundances, few endemics and a boreal,tropical disjunctionJOURNAL OF BIOGEOGRAPHY, Issue 9 2005George Y. Chiambeng Abstract Aim, We provide the first in-depth study of the Branchiopoda of the rain forests of Cameroon and also of the African continent. Location, Surface water environments, Cameroon. Methods, Qualitative plankton samples were collected in all types of surface water environments present, ranging from big lakes to water collected in rock crevices or fallen fruit cavities. A tow or hand-held plankton net of mesh size 100 ,m was used, and water volumes filtered were at least several m3 in large water bodies, or half to whole water volume in small water bodies. Results, We recorded 61 species (53 first records for the country), based on 700+ samples collected between September 1998 and March 2002. Anomopoda (92%) was the dominant order, followed by Ctenopoda (6.5%) and Cyclestherida (1.5%). Chydoridae (67%) was the most speciose family followed by Macrothricidae (6.5%) and Daphniidae (5%). Alona (11%) was the dominant genus followed by Chydorus (10%) and Pleuroxus (8%). Several species of Chydorinae, especially of the genus Pleuroxus, are shared with continental Eurasia,North America, but are absent from the Mediterranean and desert,steppe,savanna zones of Africa (boreal,tropical disjunction). Daphnia was absent, as in most tropical lowlands. No single species was really abundant, and a majority were rare to very rare, and of restricted occurrence within the rain forest patches. Comparing Africa, South America and Southeast Asia, we found a current total of 196 species for the combined rain forest areas, out of a world total of 500+ species. Systematic trends in richness at three taxonomic levels were the same for all continents: Anomopoda,Ctenopoda,Cyclestherida at ordinal level, Chydoridae,Daphniidae,Macrothricidae,Sididae at family level and Alona,Chydorus,Macrothrix,Diaphanosoma at genus level. Southeast Asia was richest (111 species, 14 endemics) with South America a close second (110 species, 27 endemics). Africa was the most species-poor (95 species, of which only 5 are endemics). Main conclusions, We hypothesize that the post-Miocene cooling and aridization of the world climate hit the freshwater biota of Africa particularly hard, with more extinction here than elsewhere, and little recolonization. Most extinction occurred in the savanna-desert belt, and eight disjunct boreal species (four Pleuroxus, Picripleuroxus laevis, Kurzia latissima, Alonella exigua, and Monospilus dispar) survive morphologically unchanged since pre-Pleistocene times in the Cameroon rain forest. Slow evolution thus appears typical of these cyclic parthenogenetic branchiopods in which sexual recombination occurs only at intervals. Illustrative of the same slow evolution is the fact that the two endemic cladocerans of Cameroon (Nicsmirnovius camerounensis and Bryospilus africanus) belong to tropicopolitan genera of Gondwanan age. [source] Effects of shear sheltering in a stable atmospheric boundary layer with strong shearTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 596 2004Ann-Sofi Smedman Abstract Data from two marine field experiments in the Baltic Sea with stable stratification have been analysed. The purpose was to test the concept of the ,detached' or ,top-down' eddies and the ,shear-sheltering' mechanism in the presence of a low-level wind speed maximum in the atmosphere. Data used include turbulence and profile measurements on two 30 m towers and concurrent wind profiles throughout the boundary layer obtained from pilot-balloon soundings. Measurements show that large eddies are being suppressed when there is a low-level wind speed maximum present somewhere in the layer 40,300 m above the water surface and when the stratification is slightly stable. The effect is seen both in normalized standard deviations of the velocity components and in corresponding component spectra. In previous work it was argued that the relatively large eddies, which dominate the low wave number spectra in measurements in the surface layer, are detached or top-down eddies generated higher up in the boundary layer, that interact with the surface layer. The low-level wind maximum introduces a distinct layer with strong vorticity which, according to the shear-sheltering hypothesis, prevents these eddies from penetrating downwards. In the limit of the wind maximum occurring at a very low height (less than about 100 m), usual turbulence statistics characteristic of the ,canonical' boundary layer are found. Combining all the statistics, it is demonstrated that the wavelength of maximum spectral energy is locally related to a turbulence length-scale, which shows that for values of the Richardson number of unity or less the effect of the local wind gradient is greater than that of static stability. The reduction of length-scale with the strength of a low-level wind maximum, explains the observed reduction (by a factor of two) of the turbulent flux of sensible heat at the surface. This result indicates that the shear-sheltering mechanism is likely to play an important role in the turbulent exchange process at the surface in sea areas where low-level wind maxima are a frequently occurring phenomenon, such as the Baltic and other large water bodies surrounded by landmasses. Copyright © 2004 Royal Meteorological Society [source] Morphological divergence of North-European nine-spined sticklebacks (Pungitius pungitius): signatures of parallel evolutionBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010GÁBOR HERCZEG Parallel evolution is characterised by repeated, independent occurrences of similar phenotypes in a given habitat type, in different parts of the species distribution area. We studied body shape and body armour divergence between five marine, four lake, and ten pond populations of nine-spined sticklebacks [Pungitius pungitius (Linnaeus, 1758)] in Fennoscandia. We hypothesized that marine and lake populations (large water bodies, diverse fish fauna) would be similar, whereas sticklebacks in isolated ponds (small water bodies, simple fish fauna) would be divergent. We found that pond fish had deeper bodies, shorter caudal peduncles, and less body armour (viz. shorter/absent pelvic spines, reduced/absent pelvic girdle, and reduced number of lateral plates) than marine fish. Lake fish were intermediate, but more similar to marine than to pond fish. Results of our common garden experiment concurred with these patterns, suggesting a genetic basis for the observed divergence. We also found large variation among populations within habitat types, indicating that environmental variables other than those related to gross habitat characteristics might also influence nine-spined stickleback morphology. Apart from suggesting parallel evolution of morphological characteristics of nine-spined sticklebacks in different habitats, the results also show a number of similarities to the evolution of three-spined stickleback (Gasterosteus aculeatus Linnaeus, 1758) morphology. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 403,416. [source] | ||||||||||