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841.
Extrapair paternity in birds has been the focus of an increasing number of studies over the last decades. Nevertheless, there is little knowledge about extrapair copulation (EPC) behavior. In this study, we investigate whether female bluethroats (Luscinia s. svecica) with no extrapair offspring (EPO) in their broods really have been sexually monogamous or if they have copulated with extrapair males. We used an experimental approach to prevent transfer of sperm from the social male during copulation by fitting a rubber tube around the cloaca of randomly chosen males. If the females mated to these males do not participate in EPCs, they will produce infertile eggs, whereas females that copulate with extrapair males will only produce EPO. We found that 87% (n=15) of the experimental pairs compared to only 36% (n=51) of unmanipulated pairs produced EPO. Our result therefore suggests that females having no EPO may still have copulated with extrapair males and that promiscuity may be an obligate sexual strategy among bluethroat females.Communicated by S. Pruett-Jones 相似文献
842.
群落中物种多度格局的研究综述 总被引:4,自引:0,他引:4
张金屯 《生态与农村环境学报》1997,(4)
物种多度格局是群落结构的重要内容,但在目前的生态学研究中对其重视不够;多度格局研究早在30年代就开始,在过去的数十年中得到了重要发展;现已建立了多种多度格局模型,它们各有所长;多度格局与物种多样性指数结合,对群落结构研究更具意义;在多度格局研究中也有一些问题值得讨论。 相似文献
843.
Markus Metz Georg M. Klump Thomas W. P. Friedl 《Behavioral ecology and sociobiology》2007,61(9):1369-1381
The red bishop (Euplectes orix) is a highly polygynous and colonial weaverbird. Males construct several nests within their territories to which they try
to attract females, and females are solely responsible for incubation and raising offspring. In this paper, we describe the
characteristics of the red bishop’s mating system as a biological market and investigate the role of nests built by males
as a traded commodity in a mating market. As timing of breeding in red bishops in arid and semi-arid zones depends on rainfall
patterns which are often unpredictable, there are temporal changes in demand for and supply of nests within a breeding season,
with breeding activities of males and females being highly synchronised. We found that males increased their nest-building
speed with increased female breeding activity independently of rainfall, indicating that supply follows demand in this mating
market. The supply of nests was always larger than the demand for nests. Construction costs for nests increased with demand
for nests as indicated by shorter nest-building duration and shorter building delays between two consecutively built nests
at times of high breeding activity. Males as a trading class are chosen according to the age of their nests offered, with
young nests having a higher probability of being accepted by females. Furthermore, female choosiness with regard to nest age
decreased when their own market value decreased, as predicted by biological market theory. The temporal changes of breeding
activity together with the female preference for young and fresh nests require that males quickly adjust nest-building activity
to varying female demand for new nests. However, males with a better adjustment of building speed to female breeding activity
did not gain higher mating success. 相似文献
844.
The vegetative cover in semi-arid lands typically occurs as patches of individual species more or less separated from one another by bare ground. We have adapted two methods to quantify the spatial pattern of such cover from measurements across patches on transects.Transects were laid in several directions across digital maps of the land surface or across the land itself, and the distances between successive patch boundaries were measured. The distances were ranked in order, and their cumulative distributions were computed and modeled with gamma functions. The parameters of the model provided estimates of the mean distance across patches. The means for different directions were further tested for anisotropy. Transitions between classes on the transects estimate the probabilities with which the different species occur next to others (and to bare ground) and so describe the arrangement of the patches occupied by the different species.The methods were tested with data from mosaic patterns at three semi-arid sites dominated by the tussock grass Stipa tenacissima. The differences in the estimated mean boundary spacings from site to site accorded with prior qualitative assessment, as did the estimated anisotropy. The transition matrices and the estimated proportions of cover showed the dominance of the bare soil with which all the individual species are intimately associated. The transitions also suggest the presence of both positive and negative relations among the main species. Those between Stipa tenacissima and Brachypodium retusum seem to be facilitative, as do those between this grass and the shrub Anthyllis cytisoides. In contrast, Globularia alypum seems to inhibit the other species.We also estimated transition probabilities geostatistically by summing the indicator variograms of the individual species. Standard variogram models were then fitted to describe the ordered series of values, and these again produced results that accorded with visual impressions. 相似文献
845.
Metapopulation models assume that inter-patch dispersal dominantly depends on distance between patches and the dispersal capability of organisms in question. We used a spatially explicit, individual-based model to investigate the potential effect of patch constellation on the exchange of individuals between patches. We simulated migration of individuals from a start- into a target-patch with both patches having the same size and shape. Simulation experiments were carried out for four patch constellations and two different movement patterns. Our results demonstrate a substantial effect of patch constellation on the exchange of individuals. They also show that the magnitude and even the direction of this effect crucially depends on their movement pattern. We conclude that particularly for highly correlated movement patterns patch shape and constellation can not readily be ignored when modelling inter-patch dispersal between habitat-islands. 相似文献
846.
Baseline resource information in an easily accessible form is a vital starting point for developing coastal zone management.
On behalf of a wide-ranging group of organizations involved in the management of the U.K. maritime zone, the Joint Nature
Conservation Committee (JNCC) is compiling a series of 16 regional volumes. The volumes contain multidisciplinary coastal
zone resource information arranged in ten chapters under the general title ‘Coasts and Seas of the UK’. These volumes form
part of a series of paper and electronic publications of coastal information being produced by JNCC's Coastal Directories
Project and are designed to meet the needs of planners and all others involved in decision-making and management of the coast. 相似文献
847.
J. Ojeda E. Sanchez A. Fernandez-Palacios J. M. Moreira 《Journal of Coastal Conservation》1995,1(2):109-118
This paper deals with the application of satellite images to characterize some aspects of the circulation dynamics of the
Tinto-Odiel estuary using turbidity patterns as ‘natural tracers’. 15 images (Landsat TM and Spot HRV) were processed to provide
synoptic, instantaneous views of the circulation patterns under different environmental conditions. In addition, a comparison
was made between results of oceanographic field work, using biplanes and fluorescent tracers, and satellite image turbidity
patterns used as ‘ground truth’ data for specific hydroclimatic situations. This approach allowed (1) the identification and
mapping of dynamic processes of interest during a theoretical tidal cycle, (2) the elaboration of additional information on
the ‘flow schemes’ at the mouth of the estuary with improved spatial and temporal resolution, and (3) the supply of basic
data to improve the knowledge of exchange processes between estuarine and coastal waters. The results of this study are considered
to be useful for the management of the estuarine system. 相似文献
848.
The role of human actions in evolution and management of foredunes in The Netherlands and New Jersey, USA 总被引:1,自引:0,他引:1
The rationale and methods of construction of foredunes in The Netherlands and New Jersey, USA are identified and used to explain
their genesis, locations, mobility, internal and external characteristics and temporal scales of evolution. Dunes are then
ranked according to the degree they are modified by human processes. The lower level of protection required of foredunes in
New Jersey and the greater amount of modification by municipal managers and shorefront residents results in smaller dunes
and greater variety of sizes, shapes, methods of construction and alterations. As a result, humans are considered intrinsic
agents in evolution of dune landforms and landscapes. Higher, wider, better vegetated foredunes occur in The Netherlands due
to greater frequency of onshore winds and greater emphasis on sea defence at the national level. Natural processes play a
greater role in the evolution of landforms. Human actions are considered extrinsic at this scale but intrinsic at the scale
of landscapes. The change in foredunes from natural features to artifacts reveals the significance of humans in the modification
of coastal landforms and reflects the changing perception of the role of these landforms in the coastal landscape. 相似文献
849.
利用道路边大气污染的常年监测数据,对风向与无限线源成任意角的高斯内插大气扩散模式进行了系统测试,分析了影响预报精度的主要因素,在分析武汉市气象因素和天气状况的基础上,对模式进行了恰当地修正,经实测数据验证,预报准确度有了明显地提高。 相似文献
850.