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171.
172.
Bates MN Buckland SJ Garrett N Ellis H Needham LL Patterson DG Turner WE Russell DG 《Chemosphere》2004,54(10):1431-1443
Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and organochlorine pesticides were measured in the serum of a sample of the New Zealand population aged 15 years and older. This was the first study to obtain representative measures of PCDDs, PCDFs and PCBs in the adult population of an entire country. Serum samples were obtained in 1996-1997. Potentially occupationally exposed individuals were excluded. Serum samples were pooled according to stratification criteria for area of residence, ethnicity, age, and sex. Of the 80 possible strata, sufficient serum for chemical analysis was available for 60, to which 1,834 individual samples contributed. For the PCDDs and PCDFs, most 2,3,7,8-chlorinated congeners were measured in all strata, with a mean toxic equivalents concentration across all strata of 12.8 ng TEQ kg(-1) lipid. Seven PCB congeners were frequently measured, including the coplanar congeners #126 and #169, quantified in all strata. Of the pesticides and their metabolites, only beta-HCH, dieldrin and pp'-DDE were consistently detected across strata. There was a general trend of increasing concentration with age. There were no consistent differences between the sexes, or between people of Maori (the indigenous people of New Zealand) and non-Maori ethnicity. Concentrations of PCDDs and PCDFs tended to increase in a North-South direction, possibly reflecting greater levels of industrialization and population concentration, and concentrations of the pesticide products were highest in the South, possibly reflecting historical use patterns. Results were consistent with a recent study of concentrations of these compounds in the milk of first-time mothers. 相似文献
173.
Habitat Loss and Extinction in the Hotspots of Biodiversity 总被引:34,自引:0,他引:34
174.
Knowledge of the investment rules adopted by breeders and non-breeders, and the factors that affect them, is essential to
understanding cooperative breeding as part of a life-history tactic. Although the factors that affect relative contributions
to care of young have been studied in some cooperative bird species, there is little data on mammals, making coherent generalisations
within mammals and across taxa difficult. In this study, we investigate individual contributions to pup escorting, a strong
predictor of offspring provisioning, in the banded mongoose (Mungos mungo), a cooperatively breeding mammal in which reproductive skew is low. Contributions by those under a year old (which virtually
never breed) increased with age and body weight but were generally low. Among older age classes (yearlings and adults), individuals
that had not bred in the current litter generally contributed less to escorting than those that had bred (with the exception
of yearling males). In addition, females that did not breed reduced their investment if they were heavy presumably because
such females are more likely to breed in the following event and benefit from saving resources for this. The generally greater
contributions by breeders in banded mongooses contrast with the recent findings in meerkats (Suricata suricatta), another obligatorily cooperative mongoose with similar group size but wherein reproductive skew is high. Our results suggest
that relative contributions by breeders vs non-breeders are not dependent on group size but on the ratio of breeders to carers
and the probability that non-breeders will breed in the near future. 相似文献
175.
176.
Summary Checker-throated antwrens (Formicariidae: Myrmotherula fulviventris) live in lowland neotropical forests and forage from dead curled leaves in the understory. Because they search each leaf individually they provide an opportunity to study the use of potential visual cues by an insectivorous bird. Long and highly curled leaves contain the most arthropods and checker-throated antwrens were more successful when foraging at those leaves. Yet, they used leaves at random with respect to these potential cues. Antwrens spent longer searching for arthropods in each highly curled leaf than in less curled leaves. Because of this additional search time, prey capture success per unit foraging time was only slightly greater for highly curled leaves than at the average dead leaf in the aerial leaf litter. Thus, the cues that antwrens could use to locate richer leaves are those features that obscure the prey from avian predators. Unlike other foraging systems, the antwrens appear to have no reliable cues indicating more profitable foraging sites.Address for correspondence 相似文献
177.
Summary In a population of the splendid fairy-wren Malurus splendens, we describe 202 intrusions by solitary adult males in full breeding plumage into the territories of conspecifics. Intrusions were not secretive and although silent they involved conspicuous flight above the vegetation and several characteristic display elements, including petal-carrying. Fifteen intrusions were observed in the 2 months before eggs were laid, but the rest occurred during the period of nest-building and egg-laying when the breeding female was presumed to be fertile, and were by males from adjacent territories. A high level of extra-pair fertilization has previously been determined in this species and we interpret many of these intrusions as attempts by males to obtain extra-pair copulations (EPC); we call this activity philandering. The costs and benefits of EPC for males and females are discussed and the promiscuous mating strategy of M. splendens is contrasted with the persistent social pairing in stable groups of this long-lived cooperatively breeding species.Offprint requests to: I. Rowley 相似文献
178.
In this paper we describe a cryopreservation protocol followed by the culture of Symbiodinium sp. isolated from the Caribbean gorgonian Pseudopterogorgia elisabethae as a potential renewable source of the dinoflagellate symbiont. Four different freezing protocols were designed: a controlled
cooling device designed to cool at 1°C/min, a three-step protocol (−20°C for 2 h, −70°C for 2 h, liquid nitrogen-LN2), a two-step protocol (−70°C for 2 h, LN2), and a one-step protocol (LN2). All cells were stored in LN2 after cryopreservation. The cryoprotective agents (CPA) used were ethanol (EtOH) and methanol (MeOH) at 10 and 20%, and seawater
(FSW) was used as a control. Viability measurements using cell counts showed that all cryopreservation protocols were relatively
successful, and no trends were observed regarding freezing protocol or CPA used. After 19 weeks in culture the viability of
samples which had high biomass was determined by the fluorescent assay CellTiter Blue™. The most viable cultures were those
cryopreserved by a two-step protocol using 20% MeOH or 20% EtOH as a CPA. A genetic examination of the DNA of these samples
using Symbiodinium-specific PCR primers confirmed that the composition of the culture had not changed. For the first time, we report that Symbiodinium sp. isolated from a gorgonian can be cryopreserved and subsequently cultured successfully.
Lory Z. Santiago-Vázquez and Nealie C. Newberger contributed equally to this publication. 相似文献
179.
Mutation and Conservation 总被引:25,自引:2,他引:25
Russell Lande 《Conservation biology》1995,9(4):782-791
Mutation can critically affect the viability of small populations by causing inbreeding depression, by maintaining potentially adaptive genetic variation in quantitative characters, and through the erosion of fitness by accumulation of mildly detrimental mutations. I review and integrate recent empirical and theoretical work on spontaneous mutation and its role in population viability and conservation planning. I analyze both the maintenance of potentially adaptive genetic variation in quantitative characters and the role of detrimental mutations in increasing the extinction risk of small populations. Recent experiments indicate that the rate of production of quasineutral, potentially adaptive genetic variance in quantitative characters is an order of magnitude smaller than the total mutational variance because mutations with large phenotypic effects tend to be strongly detrimental. This implies that, to maintain normal adaptive potential in quantitative characters under a balance between mutation and random genetic drift (or among mutation, drift, and stabilizing natural selection), the effective population size should be about 5000 rather than 500 (the Franklin-Soulé number). Recent theoretical results suggest that the risk of extinction due to the fixation of mildly detrimental mutations may be comparable in importance to environmental stochasticity and could substantially decrease the long-term viability of populations with effective sizes as large as a few thousand. These findings suggest that current recovery goals for many threatened and endangered species are inadequate to ensure long-term population viability. 相似文献
180.
Robert W. Russell F. Lynn Carpenter Mark A. Hixon David C. Paton 《Conservation biology》1994,8(2):483-490
We examined the impact of variation in habitat quality on migrating Rufous Hummingbirds ( Selasphorus rufus ) in the California Sierra Nevada. As do other migratory species, these birds depend on "stopover" habitats en route for feeding and replenishing depleted energy stores. During seven years of study, the quality of the stopover habitat (assessed in terms of the density of nectar food resources) varied widely due to natural variation in flowering. In years when stopover habitat quality was poor, incoming body masses were low and stopover durations were long. Population densities of migrant hummingbirds at the study site were coupled to habitat quality both within and among years. These observations demonstrate important effects of stopover habitat variation on the physiological, behavioral, and population ecology of migrating hummingbirds. High-quality stopover habitats are critical links between breeding and wintering areas for many species, and their preservation should be considered an essential component of strategies aiming to conserve migratory bird populations. 相似文献