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Size Classes (size + class)
Kinds of Size Classes Terms modified by Size Classes Selected AbstractsCorrelation Between Two Size Classes of Pacific White Shrimp Litopenaeus vannamei and Its Potential Implications for Selective Breeding ProgramsJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2000Brad J. Argue Breeders may assume that the largest brood-stock shrimp were also the largest market shrimp. In this study, 120 market shrimp were individually tagged and grown to broodstock in an earthen pond. There was a significant relationship between market and broodstock weight (P < 0.001) but it was not highly correlated (r = 0.42). There was no correlation between market weight and post-market weight gain (P= 0.477; r= 0.08). Of the largest 20 broodstock, only seven were among the top 20 at market weight. If the goal of a breeding program is to select the fastest growing individuals to market, shrimp should be individually selected at market weight and not as broodstock. [source] Scale-dependent controls upon the fluvial export of large wood from river catchmentsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2009Jung Il Seo Abstract The annual fluvial export of large wood (LW) was monitored by local reservoir management offices in Japan. LW export per unit watershed area was relatively high in small watersheds, peaked in intermediate watersheds, and decreased in large watersheds. To explain these variations, we surveyed the amount of LW with respect to channel morphology in 78 segments (26 segments in each size class) in the Nukabira River, northern Japan. We examined the differences in LW dynamics, including its recruitment, transport, storage, and fragmentation and decay along the spectrum of watershed sizes. We found that a large proportion of LW produced by forest dynamics and hillslope processes was retained because of the narrower valley floors and lower stream power in small watersheds. The retained LW pieces may eventually be exported during debris flows. In intermediate watersheds, the volume of LW derived from hillslopes decreased substantially with reductions in the proportion of channel length bordered by hillslope margins, which potentially deliver large quantities of LW. Because these channels have lower wood piece length to channel width ratios and higher stream power, LW pieces can be transported downstream. During transport, LW pieces are further fragmented and can be more easily transported. Therefore, the fluvial export of LW is maximized in intermediate watersheds. Rivers in large watersheds, where the recruitment of LW is limited by the decreasing hillslope margins, cannot transport LW pieces because of their low stream power, and thus LW pieces accumulate at various storage sites. Although these stored LW pieces can be refloated and transported by subsequent flood events, they may also become trapped by obstacles such as logjams and standing trees on floodplains and in secondary channels, remaining there for decades and eventually decaying into fine organic particles. Thus, the fluvial export of LW pieces is low in large watersheds. Copyright © 2009 John Wiley & Sons, Ltd. [source] Seasonal change in offspring sex and size in Dawson's burrowing bees (Amegilla dawsoni) (Hymenoptera: Anthophorini)ECOLOGICAL ENTOMOLOGY, Issue 3 2005John Alcock Abstract., 1.,Nesting females of Dawson's burrowing bees, Amegilla dawsoni, produce a large size class of offspring, which includes daughters and major sons, and a small size class, which consists entirely of minor sons averaging half the weight of their larger siblings. Female allocation patterns change over the flight season such that the initial pattern of producing daughters shifts toward the production of both daughters and major sons in the middle of the season, and then the production of primarily minor sons in the latter part of the nesting season. 2.,In Dawson's burrowing bees, this pattern is correlated with declines in pollen and nectar availability as the nesting season progresses as well as a heightened risk of dying before the final brood cell is completed. Here, the relation between these factors and the provisioning tactics of nesting Dawson's burrowing bees is discussed. [source] Functional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.)ECOLOGY OF FRESHWATER FISH, Issue 2 2010P. Gustafsson Gustafsson P, Bergman E, Greenberg LA. Functional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.).Ecology of Freshwater Fish 2010: 19: 170,177. © 2010 John Wiley & Sons A/S Abstract ,, Terrestrial invertebrate subsidies are believed to be important energy sources for drift-feeding salmonids. Despite this, size-specific use of and efficiency in procuring this resource have not been studied to any great extent. Therefore, we measured the functional responses of three size classes of wild brown trout Salmo trutta (0+, 1+ and ,2+) when fed either benthic- (Gammarus sp.) or surface-drifting prey (Musca domestica) in laboratory experiments. To test for size-specific prey preferences, both benthic and surface prey were presented simultaneously by presenting the fish with a constant density of benthic prey and a variable density of surface prey. The results showed that the functional response of 0+ trout differed significantly from the larger size classes, with 0+ fish having the lowest capture rates. Capture rates did not differ significantly between prey types. In experiments when both prey items were presented simultaneously, capture rate differed significantly between size classes, with larger trout having higher capture rates than smaller trout. However, capture rates within each size class did not change with prey density or prey composition. The two-prey experiments also showed that 1+ trout ate significantly more surface-drifting prey than 0+ trout. In contrast, there was no difference between 0+ and ,2+ trout. Analyses of the vertical position of the fish in the water column corroborated size-specific foraging results: larger trout remained in the upper part of the water column between attacks on surface prey more often than smaller trout, which tended to seek refuge at the bottom between attacks. These size-specific differences in foraging and vertical position suggest that larger trout may be able to use surface-drifting prey to a greater extent than smaller conspecifics. [source] Size-fractionated phytoplankton biomass and its implications for the dynamics of an oligotrophic tropical lakeFRESHWATER BIOLOGY, Issue 1 2008MARÍA FERNANDA ADAME Summary 1. Size-fractionated phytoplankton biomass was examined in relation to the hydrodynamics of tropical Lake Alchichica from 1999 to 2002. 2. Alchichica is a warm monomictic lake, in which mixing takes place from late December to early March. The lake is oligotrophic (mean total chlorophyll- a concentration 4.2 ± 4.2 ,g L,1) and its phytoplankton biomass is dominated (72.3 ± 16.4%) by large individuals (>2 ,m). The degree of dominance of the large size class (nano- and microplankton) over the small size class (picoplankton) throughout the year is mainly determined by the availability of silicate and the Si/N ratio in the hypolimnion prior to the mixing period. 3. This is the first record of an oligotrophic tropical lake dominated by large size fractions of phytoplankton. Because of this dominance, the fate of most primary productivity is rapid sedimentation to the bottom followed by decomposition that promotes an anoxic hypolimnion. 4. Our findings in tropical Lake Alchichica challenge the idea that oligotrophic waters are dominated by small phytoplankton, as has been well established for the oligotrophic ocean and temperate lakes. [source] Short-term variability in physical forcing in temperate reservoirs: effects on phytoplankton dynamics and sedimentary fluxesFRESHWATER BIOLOGY, Issue 1 2007ALEXANDRINE PANNARD Summary 1. The effects of wind events on phytoplankton dynamics were investigated in two temperate reservoirs. 2. Meteorological forcing, change in physical and chemical structure of the water column and biological responses of phytoplankton communities were followed for 3 weeks in three seasons. 3. Depending on the season, the phytoplankton response differed in response to nutrient and light conditions, and to the intensity of stratification and mixing. 4. We demonstrated that, on a time scale of a few days, wind events can modify phytoplankton dynamics, in terms of size structure and exported biomass. An increase of mixing favoured the largest size class and disadvantaged the smallest size class, while an increase in stratification had the opposite effects. The short-term change in size structure was reflected in the sedimentary fluxes but with a time lag. [source] Lethal and non-lethal effects of multiple indigenous predators on the invasive golden apple snail (Pomacea canaliculata)FRESHWATER BIOLOGY, Issue 10 2004Nils Carlsson Summary 1. We investigated the individual and combined effects of two predators (the climbing perch, Anabas testudineus, and the wetland crab, Esanthelphusa nimoafi) indigenous to wetlands in Laos, on the behaviour and survival of the invasive South American golden apple snail (Pomacea canaliculata). The snail is considered a pest, consuming large amounts of rice and other aquatic vegetation in the region. 2. Snail avoidance reactions to released predator chemical cues were investigated in aquaria while the effects of predators on a mixed snail population were studied in field enclosures that contained native aquatic plants (Salvinia cucullata, Ludwigia adscendens and Ipomoea aquatica). 3. In the aquaria experiment, neonate (2,3 mm) and medium-sized snails (8,10 mm) responded to fish chemical cues by going to the surface, whereas adult snails (35,40 mm) went to the bottom. In contrast, no size class of snails reacted to chemical cues released by crabs. 4. In the field experiment, fish reduced the abundance of neonate snails, and crabs reduced the abundance of all size classes. The effect of the combined predators could not be predicted from the mortality rate observed in single predator treatments. The survival of neonate and medium-sized snails was greater and of adults less than expected. The presence of predators did not affect egg production. Snails consumed significant amounts of plants despite the presence of predators. 5. Our findings suggest that some indigenous Asian predators have lethal and sublethal effects on P. canaliculata that depend on snail size and predator type. When in the presence of several predators the response of snails to one predator may either increase or decrease the vulnerability of snails to the others. [source] Tree growth is related to light interception and wood density in two mixed dipterocarp forests of MalaysiaFUNCTIONAL ECOLOGY, Issue 3 2005D. A. KING Summary 1The development of simple predictors of tree growth is important in understanding forest dynamics. For this purpose, tree height, crown width in two perpendicular directions, trunk diameter at 1·3 m height (d.b.h.) and crown illumination index (CI) were determined for 727 pole-sized trees (8,20 cm d.b.h.) of 21 species, on forest dynamics plots at Pasoh Forest Reserve, Peninsular Malaysia and Lambir Hills National Park, Sarawak, Malaysia. A light-interception index (LI = AcrCI2, where Acr is crown area) was calculated for each tree, and wood density (stem wood dry mass/fresh volume) was estimated for each species from reported values. 2Diameter growth rates were linearly correlated with LI (mean per species r2 = 0·45, excluding substantially damaged and vine-covered trees). 3Among trees of all species, diameter growth rate was highly correlated with LI/wood density. 4Mean growth rate per species varied 10-fold among the study species, but increased linearly with mean LI/wood density ratio (r2 = 0·78), consistent with the previous pattern. 5Thus much of the variability in tree growth rates, both within and among species, can be accounted for by the simple mechanistic assumption that, within a given size class, growth is proportional to light interception/wood density. [source] Non-random patterns in the Yellowstone ecosystem: inferences from mammalian body size, order and biogeographical affinityGLOBAL ECOLOGY, Issue 2 2007Judsen E. Bruzgul ABSTRACT Aim, Our aim was to investigate how the environment, species characteristics and historical factors at the subcontinental scale affect patterns of diversity. We used the assembly of the Yellowstone biota over the past 10,000 years as a natural experiment for investigating the processes that generate a modern non-volant mammal species pool. Location, The data represent species from throughout North America with special attention to the non-volant mammals of Yellowstone National Park, USA. Methods, We used digitized range maps to determine biogeographical affinity for all non-volant mammals in the Rocky Mountains, Deserts and Great Plains biogeographical regions of North America. This biogeographical affinity, along with taxonomic order and body size class, was used to test whether non-random patterns exist in the assemblage of Yellowstone non-volant mammals. These characteristics were also used to investigate the strength of non-random processes, such as habitat or taxon filtering, on particular groups of species or individual species. Results, Our results indicated that the Yellowstone fauna is composed of a non-random subset of mammals from specific body size classes and with particular biogeographical affinities. Analyses by taxonomic order found significantly more Carnivora from the Rocky Mountains region and significantly fewer Rodentia from the Deserts region than expected from random assembly. Analyses using body size classes revealed deviations from expectations, including several significant differences between the frequency distribution of regional body sizes and the distribution of those species found within Yellowstone. Main conclusions, Our novel approach explores processes affecting species pool assembly in the Yellowstone region and elsewhere, and particularly identifies unique properties of species that may contribute to non-random assembly. Focusing on the mechanisms generating diversity, not just current diversity patterns, will assist the design of conservation strategies given future environmental change scenarios. [source] Effects of surfactant replacement on alveolar overdistension and plasma cytokines in ventilator-induced lung injuryACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2010H. WU Background: Overdistension of the lung causes ventilator-induced lung injury (VILI) accompanied by surfactant abnormalities and inflammatory changes. We investigated the effects of surfactant replacement on overdistension of the terminal airspaces and plasma cytokine levels in VILI. Methods: VILI was induced by high-pressure ventilation (HPV) in rats anesthetized with pentobarbital, followed by ventilation for 2 h in the maintenance mode (tidal volume=10 ml/kg, positive end-expiratory pressure=7.5 cmH2O) with or without surfactant replacement. The sizes of the terminal airspaces were determined after fixing the lungs at an airway pressure of 10 cmH2O on deflation. Cytokine levels were assessed by enzyme-linked immunosorbent assay. Results: The mean ratio of the largest terminal airspace size class (,64,000 ,m2) was increased from 13.4% to 32.0% by HPV (P<0.05). After maintenance-mode ventilation, the ratio decreased to 16.1% with surfactant replacement (P<0.05), but increased to 44.6% without surfactant replacement (P<0.05). Mean macrophage inflammatory protein-2 (MIP-2) levels in the plasma increased from <0.02 to 6.9 ng/ml with HPV (P<0.05), and further increased to ,11.8 ng/ml, regardless of surfactant replacement after maintenance-mode ventilation. Similar tendencies were observed in the interleukin (IL)-6 and IL-10 levels. Tumor necrosis factor-, levels were almost negligible during the experiment. Conclusion: In rats with VILI, surfactant replacement reversed overdistension of the terminal airspaces that may induce barotrauma, but not upregulation of MIP-2, IL-6, and IL-10 within 2 h. [source] Feeding habits and trophic levels of bluefin tuna Thunnus thynnus of different size classes in the Mediterranean SeaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2007G. Sarà Summary Possible changes in diet and trophic levels in relation to size of Mediterranean bluefin tuna, Thunnus thynnus, were investigated using labelled carbon (,13C) and nitrogen (,15N) stable isotopes. Samples were obtained from two locations in the southern Tyrrhenian Sea (Western Mediterranean Sea) in May and October 2004. The ,13C and ,15N analyses revealed at least three significant isotopic groups [small juveniles (0.7,2.2 kg), sub-adults (15,50 kg) and adults (70 to 225 kg)]. ,13C was negatively dependent on weight, while ,15N was positively dependent on weight [TW = 8.2 (±0.16) + 0.03 (± 0.0) *,15N (n = 49; r = 0.91; P < 0.001)]. Different prey contribution to the diet was highlighted for each class. The diet of juveniles comprised zooplankton, small pelagic fish and some coastal fish; sub-adults relied on medium pelagic fish, shrimps and cephalopods, and adults relied mainly on cephalopods and larger fish. The trophic level (TL) of tunas belonging to each size class was closely correlated to weight, starting from ca 3.0 TL for Group I and reaching 4.4,4.8 TL for the giants. Bluefin tuna, from small juveniles to giants, showed a shift in feeding preferences due to different use of habitats and food items as a function of the life stage. [source] Effects of secondary tuber harvest on populations of devil's claw (Harpagophytum procumbens) in the Kalahari savannas of South AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2010Kristine M. Stewart Abstract Devil's claw (Harpagophytum procumbens) is an internationally traded species that is harvested for its secondary tubers. Root extracts are used to treat arthritis and other inflammatory diseases. This study examined population structure, density, growth, mortality, and seed and fruit production in harvested and unharvested populations in the Kalahari savannas of South Africa over 4 years. Plant density and population structure differed significantly between overgrazed and grass-dominated areas, suggesting that the differences may be due to competition for water and nutrients. Experimental removal of secondary tubers (harvest) was not a significant factor for mortality in any of the harvested size classes. Harvest also did not affect growth, although plants in the 3,4 cm size class grew more in both the harvested and unharvested populations. Fruit production was variable; fruits matured only after sufficient rains. Under the conditions of this study, the species appears to be resilient to harvest, with both harvested and unharvested plants surviving. After harvest, both groups recovered and grew (on average) at the same rate. Because of the spatially variable habitat and the plasticity of the plants themselves, a large number of plants over a wide area are required to better understand the species' life history. Résumé La griffe du diable Harpagophytum procumbens est une espèce qui est commercialisée à l'échelle internationale; on en récolte les tubercules poussant sur les racines secondaires. Les extraits de racines sont utilisés pour traiter l'arthrite et d'autres maladies inflammatoires. Cette étude examine la structure de sa population, sa densité, sa croissance, sa mortalité et sa production de semences et de fruits chez les populations récoltées ou non des savanes du Kalahari en Afrique du Sud, pendant quatre ans. La densité des plantes et la structure des populations différaient significativement entre les zones surpâturées et celles où les herbes dominaient, ce qui suggère que les différences pourraient être dues à la compétition pour l'eau et les nutriments. Le prélèvement expérimental des tubercules secondaires (récolte) n'était un facteur significatif de mortalité dans aucune des classes de taille récoltées. La récolte n'affectait pas non plus la croissance, même si les plants de la classe de taille des 3,4 cm croissaient plus chez les populations aussi bien récoltées que non récoltées. La production de fruits était variable; les fruits n'arrivaient à maturité qu'après des pluies suffisantes. Dans les conditions où fut réalisée cette étude, les espèces ont semblé résilientes à la récolte, les plants récoltés survivant aussi bien que ceux qui ne l'avaient pas été. Après la récolte, les deux groupes se rétablissaient et croissaient (en moyenne) au même rythme. Étant donné que l'habitat est très variable selon les endroits et vu la plasticité des plantes elles-mêmes, il faut étudier un grand nombre de plantes sur une grande superficie pour mieux comprendre l'histoire complète de cette espèce. [source] The production, storage and viability of seeds of Acacia karroo and A. nilotica in a grassy savanna in KwaZulu-Natal, South AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 3 2003Michele Walters Abstract African Acacias are often major contributors to the progressive increase in the woody component of savannas, a phenomenon commonly referred to as bush encroachment. They produce large quantities of seed and may have large soil-stored seed banks. In Hluhluwe,Umfolozi Park, the number of adult Acacia nilotica trees per hectare far exceed that of A. karroo adults. The relative dominance is reversed in the juvenile stage with A. karroo outnumbering A. nilotica threefold outside closed woodlands. Acacia karroo trees were smaller than A. nilotica trees on average, but produced more seeds for a given basal diameter size class. Acacia karroo showed less bruchid infestation than A. nilotica at all stages of pod development. Unlike A. nilotica, a proportion of A. karroo seeds was able to germinate after bruchid attack. We detected no difference between the two species in the soil-stored seed bank or in the viability of seeds found in the seed bank. Résumé Les acacias africains sont souvent des contributeurs majeurs de l'augmentation progressive des composants ligneux de la savane, un phénomène connu comme l'envahissement du bush. Ils produisent de grandes quantités de semences et il peut y avoir de grands stocks de semences dans le sol. Dans le Parc de Hluhluwe-Umfolozi, le nombre d'Acacia nilotica adultes par hectare dépasse de loin celui d'A. karroo adultes. Cette dominance relative est inversée au stade juvénile, les A. karrooétant trois fois plus nombreux que les A. nilotica en dehors des forêts fermées. Les Acacia karroo sont en moyenne plus petits que les A. nilotica, mais ils produisent plus de graines pour une classe de diamètre donnée. Les A. karroo présentent une moindre infestation par les bruchidés que les A. nilotica, à tous les stades de développement de la gousse. Contrairement aux graines d'A. nilotica, une certaine proportion de celles d'A. karrooétaient capables de germer après une attaque de bruchidés. Nous n'avons décelé aucune différence entre les deux espèces en ce qui concerne le stock de graines dans le sol ou la viabilité des semences que l'on y trouve. [source] Demographic factors and genetic variation influence population persistence under environmental changeJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2009YVONNE WILLI Abstract Population persistence has been studied in a conservation context to predict the fate of small or declining populations. Persistence models have explored effects on extinction of random demographic and environmental fluctuations, but in the face of directional environmental change they should also integrate factors affecting whether a population can adapt. Here, we examine the population-size dependence of demographic and genetic factors and their likely contributions to extinction time under scenarios of environmental change. Parameter estimates were derived from experimental populations of the rainforest species, Drosophila birchii, held in the lab for 10 generations at census sizes of 20, 100 and 1000, and later exposed to five generations of heat-knockdown selection. Under a model of directional change in the thermal environment, rapid extinction of populations of size 20 was caused by a combination of low growth rate (r) and high stochasticity in r. Populations of 100 had significantly higher reproductive output, lower stochasticity in r and more additive genetic variance (VA) than populations of 20, but they were predicted to persist less well than the largest size class. Even populations of 1000 persisted only a few hundred generations under realistic estimates of environmental change because of low VA for heat-knockdown resistance. The experimental results document population-size dependence of demographic and adaptability factors. The simulations illustrate a threshold influence of demographic factors on population persistence, while genetic variance has a more elastic impact on persistence under environmental change. [source] Hunger, light level and body size affect refuge use by post-settlement lingcod Ophiodon elongatusJOURNAL OF FISH BIOLOGY, Issue 4 2006M. E. Petrie Using experimental methods, body size, nutritional state (hunger) and light level were investigated as possible determinants of the extent to which juvenile lingcod Ophiodon elongatus used structural refuges. In the laboratory, older, larger individuals (134,162 mm total length, LT) exhibited a higher propensity for structure use than did smaller juvenile fish (78,103 mm LT). In fish of both body sizes, increasing hunger levels caused fish to emerge more readily from refuges than satiated individuals, with this effect most prominent for smaller fish. Diel patterns of ambient illumination were simulated in the laboratory, and refuge use by large individuals decreased significantly in response to lower nocturnal light levels, a pattern that was not observed in the smaller size class. These results indicate an ontogenetic shift in refuge use. During the summer, as post-settlement fish grew larger, they tended to increase affinity for structurally complex habitat, and also showed divergent patterns of behaviour in relation to hunger and light level. [source] HOMOTHALLIC AUXOSPORULATION IN PSEUDO-NITZSCHIA BRASILIANA (BACILLARIOPHYTA),JOURNAL OF PHYCOLOGY, Issue 1 2009Sonia Quijano-Scheggia Most pennate diatoms are allogamous, and various types of mating systems have been described. In Pseudo-nitzschia, reproductive stages have been identified in some species, and it is generally accepted that the genus is mainly heterothallic. Here we report homothallic auxosporulation of Pseudo-nitzschia brasiliana Lundholm, Hasle et G. A. Fryxell. To our knowledge, this is the first verified description of homothallic sexual reproduction in the genus. Auxospore formation was observed in all 16 subclones derived from three initial clonal cultures of P. brasiliana. Pairing was followed by production of two gametes per gametangium, which fused to give two zygotes. Each zygote (early auxospore) was initially spherical and adhered to one girdle band of the parental frustule. The two auxospores tended to expand parallel to each other and perpendicular to the parental frustule. Elongation was synchronous, slightly asynchronous, or totally asynchronous. The entire process of sexual reproduction, from gamete formation to the appearance of the initial vegetative cells, took 2,4 d. The occurrence of sex in a homothallic species seems an advantageous life strategy for this species in that any encounter between cells of the right size class is potentially sexual. [source] Evaluating land use/land cover changes and fragmentation in the Camili forest planning unit of northeastern Turkey from 1972 to 2005LAND DEGRADATION AND DEVELOPMENT, Issue 4 2007F. Sivrikaya Abstract Changes in land use/land cover have important consequences on the management of natural resources including soil and water quality, global climatic systems and biodiversity. This study analysed the spatial and temporal pattern of land use/land cover change in the Camili forest planning unit that includes the Camili Biosphere Reserve Area within the Caucasian hotspot, in the northeast corner of Turkey. To assess the patterns during a 33-year period, the necessary data were obtained from forest stand maps and evaluated with Geographic Information Systems and FRAGSTATS. Results showed that the total forested areas increased from 19,946·5,ha (78·6% of the study area) in 1972 to 20,797·3,ha (81·9 per cent) in 2005 with a slight net increase of 851,ha. Softwood cover types (411·8,ha) completely transitioned to other cover types over 33-year period. In terms of spatial configuration, the total number of forest fragments increased from 172 to 608, and mean size of forest patch (MPS) decreased from 147·7,ha to 41·8,ha during the period. Nearly 84 per cent of the patches in 1972 and 93 per cent of them in 2005 generally seem to concentrate into 0,100,ha patch size class, indicating more fragmented landscape over time that might create a risk for the maintenance of biodiversity of the area. There were apparent trends in the temporal structure of forest landscape, some of which may issue from mismanagement of the area, social conflict, and illegal utilization of forest resources due to ineffective forest protection measurements. The study revealed that it is important to understand both spatial and temporal changes of land use/land cover and their effects on landscape pattern to disclose the implications for land use planning and management. Copyright © 2007 John Wiley & Sons, Ltd. [source] A simple laser photogrammetry technique for measuring Hector's dolphins (Cephalorhynchus hectori) in the fieldMARINE MAMMAL SCIENCE, Issue 2 2010Trudi Webster Abstract The ability to measure and age individuals within a population has many important applications, for example, for examining growth and determining size class. We developed a simple photogrammetric system using two parallel lasers and a digital camera, in order to measure dorsal fin dimensions of free-ranging Hector's dolphins. Laser dots were projected onto the fin, providing scale, thus allowing measurement as well as simultaneous photo-ID of 34 individuals from fin nicks and other marks. Multiple measurements (,5) were available for six individuals; these resulted in mean CVs of 3.71% for fin length and 3.76% for fin height. Errors due to variations in angle and measurement were quantified via photography of a fiberglass Hector's dolphin model. Allometric measurements and age data were collated from 233 autopsied Hector's dolphins. Using these data, fin length was found to be a better predictor of total length (females r2= 0.732, males r2= 0.678) than fin height. Gompertz age/length growth curves were fitted to these individuals. Linear regressions were used to estimate total length for 34 individuals from laser-metrically estimated fin base length. Individuals were then assigned one of three age categories. This system shows promise as a noninvasive way of measuring individuals, while allowing simultaneous photographic identification. [source] Demographic genetics of American beech (Fagus grandifolia Ehrh.) IV.PLANT SPECIES BIOLOGY, Issue 3 2008Development of genetic variability, gene flow during succession in a coastal plain forest in Maryland Abstract Genetic recovery of an American beech (Fagus grandifolia) population in deciduous forests that were once pastures was studied using 16 allozyme loci from 410 individuals in a 600 m × 600 m study plot in Maryland, USA. We also examined the spatio-temporal genetic structure of the American beech population at a regional scale. Overall genetic diversity of mature trees was measured by estimating average heterozygosity (H = 0.156). Rare alleles were observed in five loci, Lap, 6Pdgh3, Pgi, Adh1 and Got3. Mature individuals were divided into three size classes based on d.b.h. The genetic component of each size class was compared and it was revealed that several alleles (Pgm-a, 6Pgdh3-a and Lap-b) were shared only in specific size classes. The spatial distribution of the genotypes demonstrated a conspicuous localization in three loci (Aco, Adh1 and Idh). Spatial autocorrelation analyses were carried out among the mature trees for a 20 m interval, and were positive for 0,120 m and negative for >180 m. Distrograms indicated that a unique genetic localization occurs among mature individuals. Seven hundred and seventy-five seedlings in the 10 m × 120 m transect were analyzed to measure gene flow via seed and/or pollen. We obtained a genetic neighborhood area of 1.17 ha and an effective population size of 32.4. The temporal and spatial modes of genetic recovery of the population are discussed in the context of conservation biology. [source] Effects of turbidity on feeding of the young-of-the-year pikeperch (Sander lucioperca) in fishpondsAQUACULTURE RESEARCH, Issue 2 2010Priit Zingel Abstract The effect of water turbidity on the prey selection and consumption of the young-of-the-year (YOY) pikeperch in the planktivorous feeding stage was studied. Attention was paid particularly to the question of how the food selectivity depends on the size of YOY pikeperch and how the turbidity affects feeding in different size classes. Studies were carried out in ponds of two fish farms in Estonia over 4 years. Small cladocerans were the most preferred prey in the smallest pikeperch size class. In larger size classes, the most selected prey were the large cladocerans. Water turbidity affected the prey selection of the planktivorous pikeperch significantly. In more turbid environments, the larger zooplankters were more positively selected than the smaller ones. Turbidity decreased both total zooplankton consumption and Fulton's condition factor of fish only in the largest size class of pikeperch. The effect of turbidity on foraging and growth, and thus on the size of juvenile pikeperch of a particular year class is substantial under conditions where juveniles cannot shift from planktivory to piscivory. [source] Managing invasive carp (Cyprinus carpio L.) for habitat enhancement at Botany Wetlands, AustraliaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2005L. Pinto Abstract 1.In Australia, the carp Cyprinus carpio L. is regarded as a threat to the native fish and the aquatic environment. In recent years, Botany Wetlands, a significant coastal wetland in the Sydney region, has been invaded by the undesirable cyprinids, carp and goldfish (Carrasius auratus L.). 2.In 1996 a cyprinid removal programme commenced at Botany Wetlands with the objective of managing the invasive species, increasing fish diversity, reducing cyanobacterial blooms and hence enhancing the aquatic habitat. Using electrofishing and gill netting, 4073 carp and 261 goldfish, amounting to 10 117 kg of cyprinid biomass were removed between 1996 and 2004. The captured carp ranged from 60 to 835 mm. Males matured before females. Carp between 350 and 680 mm in length grew at the rate of 1.66±0.38 g day,1. 3.The success of the programme was monitored by assessing four indicators related to carp populations and two related to habitat. The former included the pattern of length,frequency distribution, mean weight per size class, condition factor (CF) and the catch per unit effort (CPUE), and the latter the Secchi disc transparency and cyanobacterial counts. After 8 yr of removal, the plots of carp length,frequency distribution flattened, CF decreased from 2.86 to 1.82 and CPUE decreased from 97 kg day,1 to 50 kg day,1. A 10-fold decrease occurred in cyanobacterial counts and the Secchi disc transparency increased by 20%. More than 20 000 fingerlings of native Australian bass Macquaria novemaculeata (S.) have been introduced to the wetlands, increasing the potential for juvenile carp predation and biodiversity. Copyright © 2005 John Wiley & Sons, Ltd. [source] Frugivory and Seed Dispersal by the Lowland Tapir Tapirus terrestris in the Peruvian AmazonBIOTROPICA, Issue 2 2010Mathias W. Tobler ABSTRACT The lowland tapir Tapirus terrestris is the largest herbivore in the Neotropics and feeds on a large quantity of fruits, often ingesting the seeds and defecating them intact. Seed dispersal by the lowland tapir in the southwestern Amazon was studied by examining seeds from 135 dung samples collected between 2005 and 2007. Seeds of a total of 122 plant species were identified, representing 68 genera and 33 families. The species accumulation curve showed that more species can be expected with further sampling. Many species (45%) were only encountered once, and only 10 percent of all species were found in >10 samples, indicating that the lowland tapir is an opportunistic forager. Seed diversity showed a clear seasonal pattern and was highly correlated with fruit availability. Seed diameter ranged from <1 to 25 mm with 81 percent <10 mm diam. The size distribution of seeds found in lowland tapir dung generally followed that of seeds found in the forest, but had a lower proportion of seeds in the smallest size class (<2.5 mm) and a larger proportion found in the largest size class (20,25 mm). The diversity of seeds encountered in dung of the lowland tapir in this study was much higher than in previous studies. We conclude that the lowland tapir is a potential disperser for a large number of plant species, including many that previously have been thought to be dispersed only by large primates. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp. [source] Size-dependent species-area relationships in benthos: is the world more diverse for microbes?ECOGRAPHY, Issue 3 2002Andrey I. Azovsky Using original and literature data on species richness, I compared the species-area relations for 5 different size classes of the Arctic benthos: macrofauna sensu lato, polychaetes, nematodes, ciliates and diatom algae. The data pool covered a wide range of areas from single samples to the whole seas. Both the slopes and intercepts of the curves depended significantly on the logarithm of the mean body size of the group. The number of small species (ciliates and diatom algae) showed relatively higher local diversity but increased more slowly with the area than the number of larger ones. Thus, both ,- and ,-components of species diversity of the marine benthos were size-dependent. As a consequence, the actual relations between number of species and their physical size are spatially scale-dependent: there are many more species of smaller size classes in any one local community, but at a global scope the situation changes drastically. The possible reasons are discussed, including dispersal efficiency, rates of speciation and size-dependent perception of environmental heterogeneity. Body size is suggested to be the important scaling factor in manifestation of so-called "general ecological laws". [source] Effects of search experience in a resource-heterogeneous environment on the oviposition decisions of the seed beetle, Callosobruchus maculatus (F.)ECOLOGICAL ENTOMOLOGY, Issue 4 2006ROU-LING YANG Abstract 1.,This study investigates how female seed beetles, Callosobruchus maculatus, distribute their eggs on various-sized seeds when the size of seed was varied during the egg-laying period. 2.,Beetles were allowed to lay eggs on one of three arrays of 64 adzuki beans (Vigna angularis). Each array contained four size classes of seed, ranging from small (5.0,5.5 mm diameter) to large (6.5,7.0 mm), but differed in how they were distributed within the environment. In the most heterogeneous condition (the 64-patch design), the four sizes were interspersed, while in the least heterogeneous condition (the four-patch design) they were grouped into four separate blocks. Thus, a beetle exploring the 64-patch design would frequently encounter all four seed sizes, whereas a beetle exploring the four-patch design would only rarely encounter a change in bean size. 3.,Beetles experiencing greater seed size heterogeneity were more likely to lay eggs on larger seeds, whereas those in the blocked condition were more likely to oviposit on small seeds. Beetle responses to seed size heterogeneity suggest that the degree of preference for large seeds depends on a female's recent experience. 4.,Female beetles exhibited size discrimination throughout their egg-laying process; however, there was a trade-off between seed size and egg discrimination (i.e. avoiding those seeds already containing developing eggs) in response to the change in fitness gained from either laying on larger seeds or lower egg-load seeds during the egg-laying process. 5.,Our model provides the first evidence that evolving seed size discrimination ability is adaptive for the seed beetle with egg-discrimination ability. [source] Interdemic variation of cannibalism in a wolf spider (Pardosa monticola) inhabiting different habitat typesECOLOGICAL ENTOMOLOGY, Issue 2 2006Jeroen Vanden Borre Abstract., 1.,Cannibalism was investigated in the wolf spider Pardosa monticola (Clerck) using spiders collected from four populations with varying densities, inhabiting two different coastal dune habitat types. Sampled individuals were paired randomly and tested immediately for their cannibalism propensity. 2.,The occurrence of cannibalism was found to be influenced by the size (cephalothorax width) of both the smaller and the larger spider of a pair. Larger size differences enhanced cannibalism. 3.,Cannibalism rates were not significantly different in spiders from high-density compared with low-density populations. Cannibalism rates showed, however, large variability between habitat types, with higher rates in spiders from dune grasslands than from dune slacks. This is suggested to result from differences in prey availability throughout the growing season between both habitat types. 4.,Different size classes of spiders did not use different microhabitats, indicating that microhabitat segregation as a cannibalism-avoidance behaviour is absent in this species. [source] Gall size determines the structure of the Rabdophaga strobiloides host,parasitoid communityECOLOGICAL ENTOMOLOGY, Issue 5 2003Brian H. Van Hezewijk Abstract., 1.,The relationship between gall size and mortality of the willow pinecone gall midge Rabdophaga strobiloides (Diptera: Cecidomyiidae) was examined by determining the fate of all galls in a 30-ha area in central Alberta, Canada over 4 years. It was found that gall size has a large effect on the type and intensity of mortality experienced by the gall midge, and consequently this factor has the potential to influence the dynamics of the host,parasitoid interaction through the creation of phenotypic refuges. 2.,Total midge mortality ranged from 51% to 78% over the course of the study and was dominated by parasitism by Torymus cecidomyiae (Hymenoptera: Torymidae) and Gastrancistrus sp. (Hymenoptera: Pteromalidae) as well as predation by birds. Gall size had a strong, non-linear effect on the attack rates of each of these natural enemies. 3.,Birds attacked the smallest size classes. Torymus cecidomyiae preferentially attacked medium diameter galls and thus avoided predation by birds in smaller galls. Gastrancistrus sp. preferentially attacked the largest galls and consequently suffered lower rates of predation by both T. cecidomyiae and birds. 4.,This study emphasises the importance of understanding the interactions among mortality factors in order to describe adequately the susceptibility of R. strobiloides to parasitism and predation, and ultimately its population dynamics. [source] Using age grading by wing injuries to estimate size-dependent adult survivorship in the field: a case study of the yellow dung fly Scathophaga stercorariaECOLOGICAL ENTOMOLOGY, Issue 5 2002Dieter U. Burkhard Abstract 1. Studies of natural selection depend on estimates of longevity and mortality in the wild. In small and mobile species such as insects, direct, mark,recapture (resight), studies are difficult to perform because individuals cannot be tracked easily. 2. It was investigated whether age grading based on wing injuries alone can be used to estimate size-specific survivorship in the field in the yellow dung fly Scathophaga stercoraria (L.) (Diptera: Scathophagidae). 3. The accumulation of different types of wing injury throughout the spring and autumn flight seasons for both sexes was recorded: tears, notches (both reflecting regular wear), and large missing areas (probably due to intra- and inter-specific interactions). 4. Female longevity increased with body size in both spring and autumn, whereas male longevity increased slightly with size in spring but decreased in autumn. 5. The two sexes and males of different size classes accumulated the various types of wing injury differentially, presumably due to differential patterns of intraspecific interactions. Additionally, body size exhibited a seasonal pattern, complicating interpretation of the relationship between body size and wing injuries. 6. It is therefore concluded that estimating adult viability selection on body size using wing injuries is problematic in dung flies, and potentially also in other species. It is suggested that before this method is applied in any particular species, pilot studies should be conducted to verify whether wing injuries accumulate equally in all classes of individuals of interest. In addition, it is necessary to investigate the causes of different types of wing injury. [source] Functional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.)ECOLOGY OF FRESHWATER FISH, Issue 2 2010P. Gustafsson Gustafsson P, Bergman E, Greenberg LA. Functional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.).Ecology of Freshwater Fish 2010: 19: 170,177. © 2010 John Wiley & Sons A/S Abstract ,, Terrestrial invertebrate subsidies are believed to be important energy sources for drift-feeding salmonids. Despite this, size-specific use of and efficiency in procuring this resource have not been studied to any great extent. Therefore, we measured the functional responses of three size classes of wild brown trout Salmo trutta (0+, 1+ and ,2+) when fed either benthic- (Gammarus sp.) or surface-drifting prey (Musca domestica) in laboratory experiments. To test for size-specific prey preferences, both benthic and surface prey were presented simultaneously by presenting the fish with a constant density of benthic prey and a variable density of surface prey. The results showed that the functional response of 0+ trout differed significantly from the larger size classes, with 0+ fish having the lowest capture rates. Capture rates did not differ significantly between prey types. In experiments when both prey items were presented simultaneously, capture rate differed significantly between size classes, with larger trout having higher capture rates than smaller trout. However, capture rates within each size class did not change with prey density or prey composition. The two-prey experiments also showed that 1+ trout ate significantly more surface-drifting prey than 0+ trout. In contrast, there was no difference between 0+ and ,2+ trout. Analyses of the vertical position of the fish in the water column corroborated size-specific foraging results: larger trout remained in the upper part of the water column between attacks on surface prey more often than smaller trout, which tended to seek refuge at the bottom between attacks. These size-specific differences in foraging and vertical position suggest that larger trout may be able to use surface-drifting prey to a greater extent than smaller conspecifics. [source] Population ecology of cave armoured catfish, Ancistrus cryptophthalmus Reis 1987, from central Brazil (Siluriformes: Loricariidae)ECOLOGY OF FRESHWATER FISH, Issue 2 2007E. Trajano Abstract,,, The population ecology of Ancistrus cryptophthalmus (Reis 1987) was studied by mark,recapture technique in caves from the São Domingos karst area, State of Goiás, northeastern Brazil. Total population sizes estimated for Angélica and Passa Três Caves were 20,000 and 1000 individuals, respectively. Densities around 1.0 individuals per m2 in Angélica, Bezerra and São Vicente I Streams, and 0.6 individuals per m2 in the smaller Passa Três Stream may be considered high for cavefish standards, as well as for epigean loricariids. As expected for benthic grazers, cave catfish are highly sedentary. The distribution of size classes did not differ among caves and within the same cave throughout the studied dry seasons; on the contrary, the condition factor decreased throughout this period probably because of the progressive depletion of organic matter available as food. Low proportions of mature individuals, low growth rates (average = 0.5 mm month,1) with cases of negative growth and high longevities (8,10 years) point to a precocial lifestyle, typical of troglobitic species. [source] Effects of predator-induced visual and olfactory cues on 0+ perch (Perca fluviatilis L.) foraging behaviourECOLOGY OF FRESHWATER FISH, Issue 2 2006V. N. Mikheev Abstract,,, Foraging juvenile fish with relatively high food demands are usually vulnerable to various aquatic and avian predators. To compromise between foraging and antipredator activity, they need exact and reliable information about current predation risk. Among direct predator-induced cues, visual and olfactory signals are considered to be most important. Food intake rates and prey-size selectivity of laboratory-reared, naive young-of-the-year (YOY) perch, Perca fluviatilis, were studied in experiments with Daphnia magna of two size classes: 2.8 and 1.3 mm as prey and northern pike, Esox lucius, as predator. Neither total intake rate nor prey-size selectivity was modified by predator kairomones alone (water from an aquarium with a pike was pumped into the test aquaria) under daylight conditions. Visual presentation of pike reduced total food intake by perch. This effect was significantly more pronounced (synergistic) when visual and olfactory cues were presented simultaneously to foraging perch. Moreover, the combination of cues caused a significant shift in prey-size selection, expressed as a reduced proportion of large prey in the diet. Our observations demonstrate that predator-induced olfactory cues alone are less important modifiers of the feeding behaviour of naive YOY perch than visual cues under daylight conditions. However, pike odour acts as a modulatory stimulus enhancing the effects of visual cues, which trigger an innate response in perch. [source] | ||||||||||||||||||||||||||||||||||