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181.
182.
Erik E. Sotka 《Marine Biology》2007,151(5):1831-1838
There is a growing list of marine invertebrate herbivores known to restrict their host choices to a subset of available species,
yet the relative importance of the evolutionary forces that select for specialized feeding habits remain unclear. One such
specialist is the gammaridean amphipod Peramphithoe tea (F. Ampithoidae) that restricts its distribution to the brown laminarian seaweed Egregia menziesii in Oregon. A field survey indicated that among available seaweeds in the low intertidal zone of Boiler Bay, Oregon, Egregia housed greater than 90% of P. tea individuals. A set of laboratory-based habitat and feeding choice assays revealed that this specialized host distribution is likely the
consequence of choices made by adult P. tea. The restricted host choice is apparently maintained by at least two evolutionary forces. First, a juvenile performance assay
indicates that both Egregia and the co-occurring seaweed Alaria marginata, provide high food quality relative to other seaweeds available in the low-intertidal zone. Second, a field transplantation
experiment revealed that Egregia protects adult amphipods from becoming dislodged with wave energy more readily than did Alaria. Thus, Egregia’s value as good quality food and refuge from abiotic stress together explain the restricted host use of P. tea. A comparison with previous studies suggests that use of Egregia is not consistent across the geographic range of P. tea, suggesting the possibility that the host preferences of local populations may respond evolutionarily to geographic shifts
in seaweed communities. 相似文献
183.
Sokratis Papaspyrou Trine Gregersen Erik Kristensen Bjarne Christensen Raymond P. Cox 《Marine Biology》2006,148(3):541-550
The effects of infaunal mode of life on sediment properties, microbial reaction rates, as well as abundance and composition
of bacterial communities were studied in sediment surrounding burrows (mucus lining, oxidised wall, ambient anoxic and surface
sediment) of two closely related, but behaviourally different, nereidid polychaete worms: the facultative suspension-feeder
Nereis (Hediste) diversicolor and the obligate deposit-feeder Nereis (Neanthes) virens. Burrow sediment of the two species was collected from two adjacent (50 m distance) shallow sandy locations (Kertinge Nor,
Denmark). The burrow lining and wall of both polychaete species were enriched in organic matter originating from mucous secretions
by the inhabitants and phytoplankton trapped through irrigation. This was more evident for N. diversicolor that shows a significantly higher irrigation rate than N. virens. Both the organic matter mineralisation rates (based on anaerobic incubations) and bacterial abundance were higher along
the burrow linings and walls. However, accumulation of porewater TCO2 and dissolved organic carbon in sediments adjacent to burrows increased most rapidly in the presence of N. diversicolor, suggesting higher heterotrophic activity associated with this species. Surprisingly, bacterial abundance was lower around
burrows of N. diversicolor than those from N. virens indicating that burrow environments from the first species harbour a more active bacterial community. Molecular fingerprints
of the 16S rRNA gene from bacterial communities showed that the composition of the burrow linings and walls resembled the
ambient anoxic sediment rather than the oxic sediment surface. On the other hand, the bacterial fingerprints of the sediment
surrounding the burrows of the two polychaete species were markedly different suggesting either a site-specific difference
in sediment parameters or a significant species-specific impact of the burrow inhabitants. 相似文献
184.
Mats Olsson Thomas Madsen Erik Wapstra Bengt Silverin Beata Ujvari Håkan Wittzell 《Behavioral ecology and sociobiology》2005,58(3):289-294
Good genes are genetic elements that contribute to lifetime reproductive success, regardless of an individuals additional genotype. Their existence is debated, and most work has targeted their viability benefits to the offspring of choosy females. In the present study, we analyze a case of potential good genes effects in adult male sand lizards (Lacerta agilis). We show that males with a particular RFLP (Restriction Fragment Length Polymorphism) MHC genotype (O-males), as opposed to those that lack this genetic element (NO-males), have less ectoparasites under increasing physiological stress (indexed by baseline corticosterone level), and are not constrained by parasites at production of status coloration. Furthermore, O-males are more successful at mate acquisition and guard their partners longer. Ultimately, they have a higher genetic reproductive success as assigned by microsatellites.Communicated by W. Cooper 相似文献
185.
186.
The use of principal components analysis for the quality control of a mass spectrometer is demonstrated and commented upon. 相似文献
187.
Ekeberg D Ogner G Fongen M Joner EJ Wickstrom T 《Journal of environmental monitoring : JEM》2004,6(7):621-623
A method for determination of the climate gases CH4, CO2 and N2O in air samples and soil atmosphere was developed using GC-MS. The method uses straightforward gas chromatography (separation of the gases) with a mass spectrometric detector in single ion mode (specific determination). The gases were determined with high sensitivity and high sample throughput (18 samples h(-1)). The LOD (3sigma) for the gases were 0.10 micro L L(-1) for CH4, 20 microL L(-1) for CO2 and 0.02 microL L(-1) for N2O. The linear range (R2 = 0.999) was up to 500 microL L(-1) for CH4, 4000 microL L(-1) for CO2 and 80 microL L(-1) for N2O. The samples were collected in 10 mL vials and a 5 microL aliquot was injected on column. The method was tested against certified gas references, the analytical data gave an accuracy within +/-5% and a precision of +/-3%. The presence of < or = 10% by volume of C2H2 (often used experimentally to prevent N2 formation from N2O) did not interfere with detection for the targeted trace gases. 相似文献
188.
Yarrow (Achillea millefolium L.) and 3 cryptogamic epiphytes were collected from and transplanted to 10 various locations in Denmark. The spatial and temporal variation in Pb and Cd concentrations of yarrow leaves and the cryptogams were determined. The physical structure of the plant parts, the mobility differences between the metals and the atmospheric fallout of metals at the growing site were believed to be important for the metal uptake. It was concluded, that yarrow leaves give a measure of the relative variation in deposition rates to surface of higher plants when collected at the end of a growth season, and that the geographic variation was revealed with similar accuracy by yarrow and the cryptogams. 相似文献
189.
190.
Mohammad S. Farhadinia Paul J. Johnson Alexandra Zimmermann Philip J.K. McGowan Erik Meijaard Mark Stanley-Price David W. Macdonald 《Conservation biology》2020,34(4):988-996
The persistence of endangered species may depend on the fate of a very small number of individual animals. In situ conservation alone may sometimes be insufficient. In these instances, the International Union for Conservation of Nature provides guidelines for ex situ conservation and the Convention on Biological Diversity (CBD) indicates how ex situ management can support the CBD's objectives by providing insurance policies for species. The circumstances that justify its use are uncertain. To evaluate the current in situ extinction risk and ex situ management of 43 critically endangered species of mammalian megafauna, we used nonmetric multidimensional scaling and geopolitical variables related to governance, economics, and national policy within their extant ranges. We then fitted generalized additive models to assess the contribution of each variable to the ordination. Fifteen (almost one-third) of the world's terrestrial mammalian megafauna are not the subject of any ex situ management. Seventy-three percent of these taxa occur in areas characterized by political uncertainty, such as border zones or areas affected by armed conflicts, mainly in Africa and the Middle East. A further 23% of taxa in ex situ programs do not meet sustainability criteria for inbreeding avoidance. Strategic conservation planning, such as the One Plan approach, may improve ex situ management for these taxa. Given the escalating trend in threats afflicting megafauna, ex situ management should be considered more rigorously, particularly in politically unstable regions, to achieve CBD Target 12 (prevent extinction of threatened species). 相似文献