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131.
132.
Francis C. Neat Peter J. Wright Alain F. Zuur Iain M. Gibb Fiona M. Gibb David Tulett David A. Righton Robert J. Turner 《Marine Biology》2006,148(3):643-654
Atlantic cod stocks are subdivided into geographically and biologically discrete populations; some being locally resident,
others migratory. The reasons for the variation in migration pattern and the consequences it may have for population structuring
is poorly understood. We studied a group of cod from the coastal waters of the Shetland Isles in the northern North Sea. During
the spawning season, electronic tags that record depth and temperature over time were implanted into 133 individuals and the
fish released within a few kilometres of where they were captured. Thirty-nine cod have been recaptured up to 608 days later,
throughout the year and, in all but two cases, within 15 km of their release site. Geolocation methods based on temperature
and bathymetry also suggested that the cod had a limited home range, remaining resident year-round in coastal waters. The
cod were deeper during the winter and moved to shallower water in late spring and summer. They showed diel, fortnightly and
monthly cycles in depth movement that varied much within and between individuals over the season. Residency and the individual
variability in vertical movement may reflect a combination of locally complex depth strata, variable seabed substrate and
the wide range of seasonally available prey resources. 相似文献
133.
We present an analysis of the metapopulation dynamics of the federally threatened coastal California Gnatcatcher (Polioptila c. californica) for an approximately 850 km2 region of Orange County, California. We developed and validated a habitat suitability model for this species using data on topography, vegetation, and locations of gnatcatcher pair observations. Using this habitat model, we calculated the spatial structure of the metapopulation, including size and location of habitat patches and the distances among them. We used data based on field studies to estimate parameters such as survival, fecundity, dispersal, and catastrophes, and combined these parameters with the spatial structure to build a stage-structured, stochastic, spatially-explicit metapopulation model. The model predicted a fast decline and high risk of population extinction with most combinations of parameters. Results were most sensitive to density-dependent effects, the probability of weather-related catastrophes, adult survival, and adult fecundity. Based on data used in the model, the greatest difference in results was given when the simulation's time horizon was only a few decades, suggesting that modeling based on longer or shorter time horizons may underestimate the effects of alternative management actions. 相似文献
134.
An investigation of gametogenetic cycles and spawning success in populations of Nephtys caeca and N. hombergi from the River Tyne estuary, North Shields, England, in relation to production of gonadotrophic (GH) and spawning hormones (SH) has been made, based on data collected from 1978–1984. The data show that a consistent pattern of gametogenesis and efficient spawning occurs in populations of N. caeca in north-east England, but that the reproductive cycle of N. hombergi is erratic. Premature oosorption and gametogenic failure in this latter species is associated with a low level of GH production. Following high levels of GH production, gravid females sometimes fail to spawn owing to the non-release of SH. The reproductive energetics and reproductive success of N. caeca and N. hombergi are described in relation to the observed patterns of endocrine activity and the consequent changes in population structure. 相似文献
135.
Flash competition in male Photinus macdermotti fireflies 总被引:2,自引:0,他引:2
Summary The courtship of Photinus macdermotti fireflies involves a flash code in which the male emits a pair of flashes about two seconds apart and the female responds with a flash about 1.2 s after the second flash of the male pair. The male repeats his pair of courting flashes at varying intervals of four seconds or more. Lloyd (1979, 1981 a, b) observed that rival males in Florida sometimes interject flashes between the courtship flashes of the courting male. We have found that the competitive behavior of males of the same species on Long Island, New York, was somewhat different. Rival males timed their competing flashes from either the first or second of the original males's courting flashes. When a competing flash from the rival male was timed from the first courting flash it was synchronized with the original male's second courting flash. When a competing flash was timed from the second courting flash, a delayed flash resulted which appeared after the female's response. In either case the male's display period was preserved, insuring that the female would continue to respond. Either of these rival male flashes could sometimes induce the female to respond in his direction. 相似文献
136.
Jonathan P. Evans Clelia Gasparini Andrea Pilastro 《Behavioral ecology and sociobiology》2007,61(5):719-727
Predation risk influences the duration of offspring development in many species where embryos develop from externally shed
eggs. Surprisingly, such predator-mediated effects on offspring development have rarely been explored in live-bearers. In
this paper, we use the guppy (Poecilia reticulata), a live-bearing freshwater fish, to test whether the duration of brood retention (the time from mating to parturition) is
influenced by experimental changes in the perceived level of predation. Because the swimming performance of female guppies
is impaired during late pregnancy, we predicted that females would withhold broods for shorter periods when they are exposed
to cues that signal a heightened risk of predation on adults rather than on juveniles. We therefore simulated increased risk
of predation on adults by using a combination of pike-shaped models (resembling natural predators that prey on adult guppies)
and ‘alarm substances’ derived from the skin extracts of adult conspecific females. Our results revealed that, under simulated
predation risk, female guppies produced broods significantly more quickly than their counterparts assigned to a control group
where predator cues were absent. A subsequent evaluation of offspring swimming performance revealed a significant positive
association between neonate swimming speeds and the duration of brood retention, suggesting that by accelerating parturition,
females may produce offspring with impaired locomotor skills. These findings, in conjunction with similar results from other
live-bearing species, suggest that the conditions experienced by gestating females can generate significant variation in the
timing of offspring development with potentially important implications for offspring fitness. 相似文献
137.
Astrid?Kodric-BrownEmail author Jonathan?A.?Rosenfield 《Behavioral ecology and sociobiology》2004,56(2):116-123
The importance of sexual selection in hybridization between species that evolved in allopatry is poorly understood. Even less is known about differences between populations in their resistance or susceptibility to genetic introgression with a congener. Here we examine behavioral differences between populations of the native Pecos pupfish (Cyprinodon pecosensis) and their potential effects in facilitating or retarding hybridization with an introduced congener, the sheepshead minnow (C. variegatus). We quantified competitive interactions, establishment of territories, and mating success of several naturally occurring C. pecosensis populations and an artificially created laboratory population (control) against C. variegatus. Experiments were conducted in large outdoor tanks during the summer months when high temperatures favor breeding activity in pupfish. C. pecosensis populations differed in agonistic behavior, territoriality, and in mating success when competing against C. variegatus. Differences in the competitive ability of males from different C. pecosensis populations suggest that the rate of introgression with C. variegatus may vary, depending on the population of C. pecosensis it comes in contact with. Our results suggest that large, stable C. pecosensis populations may be relatively resistant to hybridization with C. variegatus. Interpopulation variation in male behavior, shaped by sexual selection, may be important in determining the incidence and rate of hybridization between the two congeners. Experimental studies are a powerful tool in elucidating behavioral processes, such as the action of intrasexual selection, that facilitate or retard the coalescence of lineages through initial hybridization and subsequent genetic introgression after secondary contact between allopatric species.Communicated by M. Abrahams 相似文献
138.
Jonathan Levinson 《环境质量管理》1998,8(2):43-54
Environmental Information Services, Inc. (EIS) publishes detailed reports and offers custom research related to the full spectrum of environmental issues facing corporations. This article highlights several key sections from EIS's new 1998 Aerospace Industry Report. It details the environmental performance, policies, and expenditures of the largest companies in the aerospace industry. EIS industry reports contain data on five key performance criteria—toxic waste management, hazardous waste generation, penalties and enforcement actions, spills, and Superfund sites. Here we examine one of those—penalties and enforcement actions—and the policies of the three largest companies. © 1998 John Wiley & Sons, Inc. 相似文献
139.
The current debate on indicators for sustainability and life-cycle assessment of materials relies heavily on universalised systems theory, first developed by Bertalanffy in the 1950s. Various ecolabelling and environmental auditing schemes have attempted to account for all the variables required to measure the sustainability of a given product or material in relation to its resource use. The aim has always been to try and harmonise standards used to facilitate trade regardless of location and using a standard neo-classical economic framework. This paper questions the hegemonic position that synchronic systems analysis currently enjoys by proposing an alternative approach that recognises evolving and relative standards based on localised cultural and economic valuation. This alternative approach is underpinned by the concept of bioregionalism which combines physical, economic and cultural mapping of local resources using local parameters and evaluation methods. Recent bioregional research into local information on environmentally benign materials in Aberdeenshire, Scotland is used to illustrate one way of bringing a meaningful regional framework back into the debate on indicators of sustainability in relation to materiality. 相似文献
140.
A qualitative method is described, using ultraviolet spectroscopy, to determine the source origins of polycyclic aromatic hydrocarbons present in the environment. The technique takes advantage of the fact that aromatic compounds exhibit strong absorption in the ultraviolet region. It offers a fast and convenient alternative to other methods, which normally require extensive sample clean-up to avoid or limit interference from other materials during analysis. In contrast, this method requires only basic column chromatography to isolate the compounds of interest. Examples of the application of the technique are presented; the results are corroborated by those previously obtained by other methods. 相似文献