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141.
Bieke Vanhooydonck Anthony Herrel Raoul Van Damme J. Jay Meyers Duncan J. Irschick 《Behavioral ecology and sociobiology》2005,59(1):157-165
Ornaments are believed to signal an individual's ability to reproduce successfully and/or survive. Since an individual's fitness is often influenced by multiple traits (e.g. number of copulations, ability to acquire nest sites or to escape predators), which are difficult to quantify simultaneously, we examine performance traits (bite force, jumping performance) believed to be relevant to an individual's fitness. Specifically, we ask whether variation in dewlap size is related to variation in body size, bite force and jumping ability in the lizard Anolis carolinensis. Our results show that dewlap size is correlated with jumping capacity across all individuals, whereas the relationships between dewlap size, body size and bite force differ depending on sex/age class. We argue that selection against relatively large dewlaps at the transition between small mature and large mature males might be responsible for the lack of a relationship within large males. The absence or presence of a correlation between dewlap size and bite force, on the other hand, might be explained by differences in behaviour, such as territory establishment, anti-predator tactics, and/or mate choice. Our work thus suggests that selective forces influencing the evolution of ornaments may operate differently on different sexes and life-history stages. 相似文献
142.
Variations in the birth sex ratio and neonatal mortality in a natural herd of horses 总被引:3,自引:0,他引:3
Anne-Marie Monard Patrick Duncan Hervé Fritz Claudia Feh 《Behavioral ecology and sociobiology》1997,41(4):243-249
Variations in birth sex ratios and sex differences in juvenile mortality occur in a number of mammalian species, and in many
cases have been linked to resource availability. Most of these biases in offspring sex ratios concern polygynous species with
pronounced sexual dimorphism, and where females only are philopatric. Data on species with unusual life-history strategies,
such as slight sexual dimorphism or dispersal by both sexes, are of particular interest. In this study of a natural herd of
horses (Equus caballus) which experienced an eruptive cycle, and therefore a period of nutritional stress, male offspring had higher neonatal mortality
rates in nutritionally poor years than in good ones, whereas “year quality” had no effect on the mortality of female offspring;
year quality could therefore be used by mares as predictor of sex-specific offspring survival. We show that the environmental
conditions that predicted lower survival of males were negatively related to their production: the birth sex ratio the following
year was female-biased; and mares were less likely to produce a son when they had produced a son the preceding year. There
was no significant effect of mother's parity, age or rank, or the timing of conception or birth on offspring sex ratios. The
mechanism leading to biases in the birth sex ratio could have been the loss of male embryos by mares that did not foal. As
there was no evidence for selective abortion of male foetuses in females that did foal the next year, it is not necessary
to invoke maternal adjustment, though this remains a possibility. Finally, there was a suggestion that male offspring were
more costly to raise than females, since mothers that reared a son in poor years tended to experience an increase in the interbirth
interval between their two subsequent offspring.
Received: 28 December 1996 / Accepted after revision: 27 July 1997 相似文献
143.
Geographic Analysis of California Condor Sighting Data 总被引:3,自引:0,他引:3
David M. Stoms Frank W. Davis Christopher B. Cogan Marco O. Painho Brean W. Duncan Joseph Scepan J. Michael Scott 《Conservation biology》1993,7(1):148-159
Observation and habitat data were compiled and analyzed in conjunction with recovery planning for the endangered California Condor ( Gymnogyps californianus ). A geographic information system (GIS) was used to provide a quantitative inventory of recent historical Condor habitats, to measure the association of Condor activity patterns and mapped habitat variables, and to examine spatio-temporal changes in the range of the species during its decline. Only five percent of the study area within the historic range is now used for urban or cultivated agricultural purposes. Observations of Condor feeding perching, and nesting were nonrandomly associated with mapped land cover, in agreement with life history information for the species. The precipitous decline in numbers of Condors in this century produced only a small reduction in the limits of the observed species' range, as individual birds continued to forage over most of the range. Some critical risk factors such as shooting and lead poisoning are difficult to map and have not been included in the database. Besides the applications demonstrated in this case study, GIS can be a valuable tool for recovery planning, in the design of stratified sampling schemes, or for extrapolation of habitat models over unsurveyed regions. We conclude with recommendations from this case study regarding when to consider using GIS and the importance of pilot studies and sensitivity analysis. 相似文献
144.
Observations were made and quantitative samples of non-canopy kelps were collected, using SCUBA, at 9 subtidal sites off southern Kodiak Island in May, 1976. At a 10th site, only observations were made. The most abundant species in the quadrats were Laminaria dentigera, L. yezoensis, Pleurophycus gardneri, Agarum cribrosum, and Alaria marginata. We found fertile plants of all these species. L. dentigera dominated at all sampled sites except one within a bed of Nereocystis luetkeana, where P. gardneri was dominant. L. yezoensis was dominant at the site which was visited but not sampled. The average wet weight of non-canopy kelps in the 55 samples was 12 kg m-2, and the quadrat range was 2 to 35 kg m-2. The reported ranges of P. gardneri and Alaria marginata are extended westward from Montague Island (147°22W) to Bumble Bay, Kodiak Island (154°43W), where A. marginata was found at a depth of 8.5 m. 相似文献
145.
The crisis in the early 1990s over conservation of biodiversity in the forests of the Pacific Northwest caused an upheaval in forest policies for public and private landowners. These events led to the development of the Coastal Landscape Assessment and Modeling Study (CLAMS) for the Coast Range Physiographic Province of Oregon, a province containing over two million hectares of forest with a complex mixture of public and private ownership. Over a decade, CLAMS scientists developed regional data bases and tools to enable assessments of the implications of current policies for biodiversity and have begun using these data and tools to test ideas for solving policy problems. We summarize here four main lessons from our work: (1) Regional ecosystem perspectives, while rewarding, are difficult to achieve. Helping policy makers and the public understand biodiversity policies for an entire province can assist in developing more reasoned policies. However, this result is difficult to achieve because needed scientific building blocks generally do not exist, few policy institutions address regional cross-ownership issues, people can find it difficult to take a regional view, and the appropriate region for analysis changes with the policy problem. (2) Interest in environmental policy analysis may come as much from a pursuit of power as a pursuit of understanding. Biodiversity policy analyses are often viewed as weapons in an ongoing political battle. Also, results that might destabilize existing policies generally will not be well received by those in power. (3) The relationship of regional analyses to civic processes remains challenging and unsettled. Communication between citizens and scientists takes real effort. Also, collaborative processes both inspire and constrain regional policy analysis, and scientific work often proceeds at a different pace than these processes. In the end, CLAMS's most important effect on the civic dialogue may be to change how people think about the Coast Range. (4) An important role exists for anticipatory assessments done independently by scientists. Independent review will be especially important as policy analyses shift to management of nonfederal forests. Our future efforts in CLAMS will focus on evaluating ideas for fundamental changes in forest management. 相似文献
146.
147.
Christina Skarpe Per Arild Aarrestad Harry P. Andreassen Shivcharn S. Dhillion Thatayaone Dimakatso Johan T. du Toit Duncan J. Halley Hkan Hytteborn Shimane Makhabu Moses Mari Wilson Marokane Gaseitsiwe Masunga Ditshoswane Modise Stein R. Moe Rapelang Mojaphoko David Mosugelo Sekgowa Motsumi Gosiame Neo-Mahupeleng Mpho Ramotadima Lucas Rutina Lettie Sechele Thato B. Sejoe Sigbjrn Stokke Jon E. Swenson Cyril Taolo Mark Van 《Ambio-人类环境杂志》2004,33(6):254-260
博茨瓦纳北部及其毗邻地区分布着世界上最大的非洲象种群(Loxodonta africana),而在100年前,由于过度捕猎,大象的种群数量极为稀少. 相似文献
148.
N. J. Manning Mr N. P. Davies S. E. Olpin K. H. Carpenter M. F. Smith R. J. Pollitt S. L. B. Duncan A. Larsson B. Carlsson 《黑龙江环境通报》1994,14(6):475-478
Prenatal diagnosis for glutathione synthase (EC 6·3.2·3) deficiency in two pregnancies of an at-risk couple was performed on amniotic fluid taken at 16 weeks' gestation. 5-Oxoproline (pyroglutamic acid) levels were 970 and 790 μmol/l compared with the normal mean value of 29 μmol/l (range 13–51 μmol/l). The pregnancies were terminated and the diagnosis in one case was subsequently confirmed by assay of glutathione synthase in cultured fetal fibroblasts. In the other, post-mortem tissue samples failed to grow. 相似文献
149.
A range of new nanomaterials to replace the active materials in lithium ion batteries are currently being studied and employed in an attempt to overcome various performance limitations of previous technologies. Nanomaterial production and manufacturing techniques appear to fit into a general trend towards more energy intensive production methods for high-tech goods. This does not necessarily imply an increase in lifecycle energy use; artefacts that consume or transform energy during use could possibly regain this increased initial input via increased efficiency in use. In particular, this paper highlights that larger gains could be possible if the artefact in question allows a given service to be provided via an alternative and more efficient system entirely.The lifecycle energy efficiencies of lithium ion batteries constructed from several new advanced materials are analysed with several different system boundaries. Although nanomaterials require more energy input to produce, the implications of nanomaterials for energy flows in the use phase (i.e. driving), and higher levels such as the architecture of future transport fuel production systems are much larger in magnitude than the initial lifecycle inputs for producing the materials in question. 相似文献
150.
Demographic factors such as operational sex ratio (OSR) and local population density (LPD) are temporally and spatially dynamic in the natural environment but the influence of these variables on male mating success and the mechanisms behind it are still poorly understood and highly controversial. Here, we manipulated the OSR and LPD of a seed bug, Nysius huttoni, and carried out a series of mating trials to test how these variables affected male mating success. The two demographic factors had no significant interactions, suggesting that they affect male mating success independently in N. huttoni. In this species male mating success was significantly higher in both male- and female-biased OSR than in even OSR. It is suggested that, in male-biased OSR, the increased intensity of competition and interference does not result in lower male mating success; rather, males may make more effort in courting and females may have more chance to encounter better males, resulting in higher male mating success. In female-biased OSR, females may become less choosy and less likely to reject male mating attempt, leading to the higher male mating success. Lower male mating success in N. huttoni in high LPD may be due to increased interference between males and/or delayed female receptiveness for mating. OSR had a stronger effect on male mating success than LPD in N. huttoni, suggesting that OSR and LPD affect mating success in different ways and intensities. 相似文献