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1.
This study examined seasonal changes in blubber distribution and body morphology of 61 male hooded seals, 4 years of age and
older, caught in Skjalfandi-Bay in northeast Iceland in May, August and October during 1998 and 1999. Seasonal changes were
found in girth, blubber depth and the ratio of blubber depth to body radius (d/r ratio). The seals lost 16% of their total mass between May and August, during moulting, but d/r ratios did not drop significantly. Hooded seals caught in October were 10% heavier than seals caught in August mostly due
to greater sculp mass but were not as heavy as seals caught in May that had a higher core mass (mass–sculp). Core mass decreased
by 14% between May and August or almost proportionally to total mass but increased much more slowly than total and sculp mass
between August and October. Furthermore, this study found that commonly used condition indices are misleading when comparing
condition of adult male hooded seals between seasons. 相似文献
2.
Heather B. Leach Christine Van der Stege Christian R. Vogl 《Human ecology: an interdisciplinary journal》2011,39(5):597-612
The tree management practices of a Dogon village in Mali, West Africa were investigated to learn how a rural population adapts
its strategies to cope with institutional change, climate change, unequal land distribution, and expanding market access.
A range of methodologies was used, including semi-structured interviews, seasonal calendars, community mapping and matrices.
Special focus was given to baobab (Adansonia digitata L.) and tamarind (Tamarindus indica L.), two highly used and valuable trees within this community. This research reveals that community members have realized
that traditional management practices are no longer effective in dealing with the impacts of these transitions, and highlights
the fact that management practices, while historically uniform, have begun to diverge in recent years based on unequal land
and water endowments within the village. Understanding the rights and abilities of all users to access and protect these species
is crucial to their conservation. 相似文献
3.
Paweł Olejniczak 《Plant Ecology》2011,212(11):1927-1935
A positive effect of herbivory on plant reproduction (overcompensation) has been documented mostly in monocarpic plants. Iteroparous
perennials can be used to test whether enhanced reproduction in 1 year has negative future consequences as predicted by optimal
allocation models. This study was intended to verify this prediction in the iteroparous herb Sedum maximum, applying mechanically simulated herbivory. I monitored 132 labelled S. maximum individuals during 2 years of study. They were randomly assigned to two groups: clipped and control. Infructescence dry mass,
total seed dry mass, seed size, germination rate and an increase of root dry mass during the season were assessed in the experimental
plants. Since only roots can survive to the next season, root dry mass was considered a reliable measure of allocation to
future performance. Clipped plants showed increased fruit and seed dry mass versus the controls, with no other aspect of reproduction
affected. Apical bud removal also had a positive effect on increase of root dry mass. The results indicate true overcompensation
in response to simulated herbivory with no future costs of increased reproduction. Moreover, increased plant reproduction
as a result of herbivory is likely to persist in the following years: clipping increased not only seed production but also
root growth. This response is inconsistent with the results of optimal allocation models and the discrepancy is probably due
to violation of the resource limitation assumption. Plants adapted to tolerate herbivory seem not to reproduce at the maximum
rate when undamaged, but rather withhold resources to be allocated to reproduction after herbivory. 相似文献
4.
Seed mass and seedling establishment after fire in Ku‐ring‐gai Chase National Park,Sydney, Australia
Abstract Relationships between seed mass and several aspects of plant regeneration ecology were investigated in a post‐fire environment in Ku‐ring‐gai Chase National Park near Sydney, Australia. We found a significant positive relationship between seed mass and time to seedling emergence (P < 0.001) and a strong negative relationship between seed mass and time between emergence and production of the first true leaf (P < 0.001). Surprisingly, we found no relationship between seed mass and seedling establishment (P = 0.21). It seems most likely that this lack of relationship is a result of the many stochastic factors affecting seedling establishment during any given recruitment episode at any given site. A cause of mortality was assigned to 56% of the 781 seedlings that died during the present study. There was no relationship between cause of death and seed mass (P = 0.28). Of the seedlings for which the cause of death was known, 57% were killed by herbivory and 21% were killed by drought. Seedling–seedling competition affected only one species. 相似文献
5.
Antoine Fouquet David M. Green Bruce Waldman Julia H. Bowsher Katherine P. McBride Neil J. Gemmell 《Conservation Genetics》2010,11(3):907-919
Leiopelma hochstetteri belongs to a singular anuran lineage endemic to New Zealand that diverged from other frogs about 200 million years ago. The
species now is reduced to a series of isolated populations in the northern half of the North Island and Great Barrier Island.
We have used mitochondrial and nuclear sequence data to examine the genetic affinities of extant populations of L. hochstetteri. Phylogenetic reconstructions reveal that populations are highly structured. Each of the geographically isolated populations
harbours independent mtDNA lineages as well as different degrees of nuDNA differentiation. Moreover, molecular dating reveals
that this structure originated in the early Pleistocene. This pattern of genetic structure likely results from unfavourable
climatic conditions during the Pleistocene combined with the low dispersal ability of the species. Isolated populations in
forested refugia existed even in the southern part of the distribution of the species during glacial cycles. Previously published
variation in chromosome numbers and isozyme data are consistent with the new evidence. We identified 13 evolutionary significant
units (ESUs) that should serve as the focus for future management and conservation of this species. 相似文献
6.
D'Alva T Lara C Estrada-Torres A Castillo-Guevara C 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(7):707-712
The sporocarps of hypogeous and epigeous fungi are important dietary items for forest dwelling rodents in temperate and tropical
forests throughout the world. However, results of some pioneering works have demonstrated that fungi cannot be considered
as nutritionally high-quality food items for some mycophagous small rodents. According to these studies, when mycophagous
rodents feed on fungus, they showed a minimal digestibility, but whether this applies to most rodent species that include
fungi in their diets is unknown. In this study, we experimentally evaluated body mass changes and feed preferences in captive
deer (Peromyscus maniculatus) and volcano (P. alstoni) mice when fed on epigeous fungus (Russula occidentalis). In experiment 1, the animals were fed with fungus as the only feedstuff in comparison to regular rodent chow and oat. In
experiment 2, the animals were fed with fungus in a free-choice arrangement together with equal amounts of rodent chow and
oat. Both species lost ∼15% of their body mass within 4 days when fed on fungus alone, but gained 5–10% body mass during the
same time period when ingesting oat and rodent chow, respectively, as the only feedstuff. However, in contrast, in the free-choice
arrangement with all three feedstuffs, both species gained 20–30% body mass, and showed the highest feed preference for fungus
followed by oat and rodent chow. In addition, apparent digestibility of energy and nitrogen were analyzed in both rodent species,
which were 50–60% for fungus, whereas approximately 90–94% for rodent chow and oat. According to our results, animals need
to supplement their diets with alternative high-quality food items in order to maintain and increase their body mass, suggesting
that epigeous fungi are only of moderate nutritional value for small rodents. Futures studies should focus on exploring the
importance of a mixture of fungal species in the diet of small mycophagous rodents. 相似文献
7.
Beetles (Coleoptera) are a diverse and ecologically important group of insects in agricultural systems. The Environmental
Risk Assessment (ERA) of genetically modified Bt-crop varieties with insect resistances thus needs to consider and assess the potential negative impacts on non-target organisms
belonging to this group. We analysed data gathered during 6 years of field-release experiments on the impact of two genetically
modified Bt-maize varieties (Ostrinia-resistant MON810 and Diabrotica-resistant MON88017) on the occurrence and field densities of Coleoptera, especially the two families Coccinellidae and Chrysomelidae.
Based on a statistical analysis aimed at establishing whether Bt-maize varieties are equivalent to their near-isogenic counterparts, we discuss the limitations of using field experiments
to assess the effects of Bt-maize on these two beetle families. The densities of most of the beetle families recorded in the herb layer were very low
in all growing seasons. Coccinellidae and Chrysomelidae were comparatively abundant and diverse, but still low in numbers.
Based on their role as biological control agents, Coccinellidae should be a focus in the ERA of Bt-plants, but given the large natural variability in ladybird densities in the field, most questions need to be addressed in
low-tier laboratory tests. Chrysomelidae should play a negligible role in the ERA of Bt-plants, since they occur on-crop as secondary pests only. Species occurring off-crop, however, can be addressed in a similar
fashion as non-target Lepidoptera in Cry1Ab expressing Bt-maize. 相似文献
8.
Aim To assess the impacts of El Niño–La Niña events on the pup weaning mass and diet of female southern elephant seals (Mirounga leonina) feeding in the Bellingshausen Sea, Antarctica, and to understand the ecological processes that drive these impacts. Location Atlantic southern elephant seal weaning mass and diet were measured at King George Island (62º14′ S, 58º30′ W). Feeding areas for pregnant female seals from King George Island are located west of Alexander Island in the Bellingshausen Sea. Methods Data on weaning mass were collected between 1985 and 1994 during the breeding season (September–November). Moulting females were anaesthetized and cephalopod beaks were isolated and identified from stomach contents obtained from stomach lavages. Sea‐surface temperature anomaly (SSTA) data for the ‘El Niño 3.4’ geographical region (5º N–5º S, 120º W–170º W) were used to define El Niño–Southern Oscillation (ENSO) event years (grouped as El Niño, La Niña and Neutral) as well as the strength of each ENSO event year. Using data from the US National Center for Environmental Prediction, temperature, sea ice concentration and atmospheric pressure anomalies in the Bellingshausen Sea were calculated from March to August, corresponding to the feeding period of pregnant female seals. Results Positive temperature anomalies and negative pressure anomalies in the Bellingshausen Sea were observed during La Niña years and negative temperature anomalies and positive pressure anomalies during El Niño years. These data correlate with sea ice concentration anomalies, which are highly negative during La Niña years and highly positive during El Niño years. Warm temperature conditions in the Bellingshausen Sea during La Niña years are strongly related to both higher weaning mass in elephant seals and to an increase in squid beaks in the stomach contents of females. Main conclusions It is possible that higher elephant seal weaning masses in La Niña years correlate with warmer waters in the Bellingshausen Sea leading to the rapid growth of squid and their more frequent descents to depths frequented by elephant seals. This results in increased predation by pregnant females, leading to a greater mass among weaned pups. This hypothesis may guide future research about interactions between climate and the marine biosphere. 相似文献
9.
10.
S. V. Bugmyrin L. A. Bespyatova V. S. Anikanova E. P. Ieshko 《Entomological Review》2010,90(1):116-122
The data on long-term studies (1998–2004) of the population density of preimaginal stages of the taiga tick Ixodes persulcatus Schulze, 1930 collected from small mammals in deforested areas (foresting during 7, 12, and 25 years after forest cutting)
in the middle taiga zone of Karelia are given. The lowest population density of I. persulcatus was observed in the most recently deforested area. The territory where forestation lasted for 25 years after deforestation
was the most favorable biotope for the taiga tick development. Deforested areas, in comparison with secondary forests, are
characterized by significantly higher population density of preimaginal stages of ixodid ticks; this phenomenon is determined
first of all by the high population density of small mammals. 相似文献
11.
Barboza PS Hartbauer DW Hauer WE Blake JE 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(4):309-317
Reindeer are polygynous ruminants that breed when plant growth declines in the Arctic. We studied seven males (2 years and older) in two herds with a total of 34 females to describe the costs and consequences of mating or rut. Body mass declined between September and November and did not recover through winter even though food was available ad libitum. Dominance did not affect body mass or any correlate of mass loss, indicating similar costs of rut among males. Males lost 34% of ingesta-free mass in 77 days of rut, which corresponded to depletion of 23% body protein and 78% body lipid. Water flux, plasma insulin, and plasma thyroxine were minimal 23 days after the peak in body mass, indicating low food intake. Maximum plasma testosterone and cortisol also followed peak mass and coincided with the death of two males from acute infections. Loss in body protein did not increase the ratio of urea to creatinine in plasma. Increased variance in plasma osmolality and urea during mass loss indicated altered homeostatic control during rut. Mating compromises survival of males through reduction of body reserves, food intake, and maintenance of tissues. These adverse effects may be the consequence of selection for large body size and aggression in a highly variable competition for mates.Abbreviations BRI body reserve index - T3 tri-iodo-thyronine - U/C urea to creatinine ratio 相似文献
12.
Andreas Vohmann Jost Borcherding Armin Kureck Abraham bij de Vaate Hartmut Arndt Markus Weitere 《Biological invasions》2010,12(1):53-64
The filter-feeding clam Corbicula fluminea has widely spread from its Asiatic origin into freshwater habitats on several continents, where it often has a considerable
impact on ecosystem processes. The present study was stimulated by the observation that C. fluminea can experience mass mortality during warm summers, even when temperatures are still far below the lethal level. We hypothesized
that starvation due to low food quantities during summer is a main factor in this context. In order to test nutritional conditions
in an environment where summer mortality occurred, the clams’ body mass was tracked in river bypass systems installed at the
Lower River Rhine (Germany and The Netherlands). Two food levels were adjusted in the bypass channels: one corresponding to
the original chlorophyll level in the river (ambient food) and one with a chlorophyll a level reduced by about 50% (low food). The clams kept at the ambient food level increased their shell length during summer,
although growth rates decreased at low food levels in the River Rhine in late summer. In contrast to shell length, body mass
decrease in late summer cumulated in 94% reduction from August until October. This trend was enhanced by the experimental
food reduction, i.e., clams kept in the low food level treatments weighed 60% less than the clams in the ambient food treatment
at the end of summer. However, mortality was low in both treatments. The data demonstrate a high plasticity in the body mass
of C. fluminea. The corresponding possibility to respire body mass can be seen as one strategy to survive longer starvation periods. 相似文献
13.
14.
Yvonne Linn Louise Dye Britta Barkeling Stephan Rssner 《Obesity (Silver Spring, Md.)》2004,12(7):1166-1178
Objective: The aim of this study was to evaluate how well prepregnancy BMI, gestational weight gain, and postpartum weight retention predict retention of weight 15 years later among parous women. Research Methods and Procedures: The Stockholm Pregnancy and Women's Nutrition (SPAWN) study is a long‐term follow‐up study of women who delivered children in 1984 to 1985 (n = 2342). The participants initially filled out questionnaires about their eating and exercise habits, social circumstances, etc. before, during, and at 1 year after pregnancy. Anthropometric data were also sampled. Fifteen years later, these women were invited to take part in the follow‐up study. Anthropometric measurements were collected, and similar questions were asked. Five hundred sixty‐three women participated in the SPAWN 15‐year follow‐up study. The sample was divided into groups to examine three presumably critical time periods: 1) overweight and normal weight before pregnancy; 2) low, intermediate, and high weight gainers during pregnancy; and 3) low, intermediate, and high weight retainers at 1 year after pregnancy. Results: The overweight women did not gain more weight during pregnancy or retain more weight at 1 year follow‐up. High weight gainers during pregnancy retained more weight at the 1‐year and the 15‐year follow‐ups. High weight retainers had gained more during pregnancy and retained it at the 15‐year follow‐up. Fifty‐six percent of the high weight gainers during pregnancy ended up in the high weight retainers group. Discussion: Women who are overweight before pregnancy do not have a higher risk of postpartum weight retention than normal weight women. Thus, it is not necessarily the initially overweight woman who should be the target or focus of weight control programs during or after pregnancy. Both high weight gainers and high weight retainers had higher BMI at the 15‐year follow‐up, although only 56% of the high weight gainers during pregnancy were also classified as high weight retainers at the 1‐year follow‐up. Weight retention at the end of the postpartum year predicts future overweight 15 years later. 相似文献
15.
George A. Bray James P. DeLany David W. Harsha Julia Volaufova Catherine M. Champagne 《Obesity (Silver Spring, Md.)》2001,9(10):605-621
Objective: To evaluate the 2‐year changes in body composition of white and African American boys and girls. Research Methods and Procedures: A total of 114 boys and girls ages 12 to 14 years with equal sex and ethnic distribution between African American and white races participated in measurements of body composition using DXA, underwater weighing (densitometry), skinfold thickness, corporal diameters, circumferences, isotope dilution (H218O), and bioelectric impedance. Results: Sixty‐eight of the 114 children advanced from Tanner Stages 1 and 2 to Tanner Stages 3 to 5 over a 2‐year period. More than 50% of the children were in the top 15th percentile according to normative data for body mass index but not for triceps skinfold. All measures except for percentage of fat, density, and four of the six skinfolds increased significantly during the 2 years, with no differences between races, genders, or fat group. The boys who advanced in Tanner Stage reduced their percentage of fat and a number of skinfolds and increased their lean body mass, but the girls did not. The percentage of water was significantly higher in the fatter children and declined significantly over 2 years. Most children remained in the same quartile of body fat, lean body mass, and bone mineral content over 2 years. Discussion: The data are consistent with the hypothesis that over 2 years, growth is the major determinant of changing body composition, with body‐fat group and sexual maturation being additional variables. 相似文献
16.
Igor Kosiński 《Plant Ecology》2008,194(2):149-156
Relatively few studies conducted in natural plants populations focus on the relationship between seed size and their germination
ability and seedling establishment. Maianthemum bifolium is a perennial herb that spreads vegetatively through rhizomatous growth and reproduces through seeds. However, this species
is characterized as seed and microsite limited, and under undisturbed conditions seedlings are not noted. The studies were
conducted in two populations of M. bifolium in six subsequent seasons. The mean seed mass was negatively correlated both per ramet as well as in the fruit with the number
of seeds, and positively with its height and the number of flowers. The long-term mean annual production of seeds in the populations
was 37 and 56 seeds per m2. The seeds from both populations had similarly high germination abilities that were approximately 90% under laboratory conditions,
60% in garden, and 55% in the natural habitat. Seeds from four size classes were sown and a positive correlation was noted
between seedling establishment and the mass of the seeds from which they grew (rS = 0.64). Seedling survival was also significantly correlated with seed mass. 相似文献
17.
House flies (Musca domestica L.) and stable flies (Stomoxys calcitrans (L.)) (Diptera: Muscidae) are nuisance pests on livestock farms. In the present study we tested the effect of biweekly mass
release of Spalangia cameroni Perkins (Hymenoptera: Pteromalidae), the most common parasitoid of house flies and stable flies in southern Norway, on pig
premises with scattered fly breeding sites. The study spanned two successive summer periods, with two control and two release
units each year. Spalangia cameroni suppressed both house flies and stable flies in one release unit during the first year, and stable flies in one release unit
the second year. The apparent lack of success in fly control in the other release units was likely due to immigration of flies
in two of the trials and high temperatures in one trial. Recommendations concerning release of S. cameroni in similar pig production premises are given.
Handling editor: Torsten Meiners. 相似文献
18.
19.
Body mass of Brünnich's guillemots Uria lomvia breeding at Coats Island, Canada, was measured during incubation and chick‐rearing in 1988–2001. In most years, mass increased during incubation and fell after hatching, leveling off by the time chicks were 18 d old, close to the age at which chicks departed. Mass during incubation increased with age up to about 12 yr, but the mass of birds brooding chicks was not related to age. The trend towards increasing mass during incubation was mainly a consequence of mass increases of young breeders as older birds maintained a constant mass. The variation in adult mass with age during incubation seems likely to reflect age‐related variation in foraging ability, but the loss of mass after hatching, being greater for older birds, appears best explained as a response to the demands of provisioning chicks, with older birds transferring their accumulated reserves to their chicks via higher provisioning rates. 相似文献
20.
Yuan-Zuo Li Yen-Peng Ho Shui-Tein Chen Tzyy-Wen Chiou Zong-Sian Li David Shiuan 《Biochemistry. Biokhimii?a》2009,74(2):215-220
Mycoplasma hyopneumoniae is an important pathogen of pigs causing enzootic pneumonia of swine. The pathogen remains largely enigmatic as far as the
host-pathogen interactions are concerned. In the present study, the protein profiles of two strains of M. hyopneumoniae were compared by two-dimensional gel electrophoresis and mass spectrometry. The results indicate that the major adhesin P97,
the 50-kDa protein derived from P159 adhesin, and the 43-kDa cleavage product of P102 are expressed at much higher levels
in the pathogenic strain 232. In contrast, the avirulent strain J switches its focus to metabolism and expresses more glyceraldehyde
3-phosphate dehydrogenase in gluconeogenesis and lactate dehydrogenase, pyruvate dehydrogenase, and phosphate acetyltransferase
in the pyruvate metabolism pathway. We speculate that the avirulent strain may have developed better capabilities to cope
with the rich environment during repeated inoculations. Simultaneously, the capability to infect host cells may become less
important so that the adhesion-related protein genes are down-regulated.
Published in Russian in Biokhimiya, 2009, Vol. 74, No. 2, pp. 264–271. 相似文献