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1.
ANTONI HOFFMAN 《Biological reviews of the Cambridge Philosophical Society》1985,60(4):455-471
1. The concept of evolutionary equilibrium has been derived from the theory of island biogeography via an ecological rationale for increase in species extinction rate and decrease in speciation rate with increasing diversity of the system.
2. This concept is theoretically plausible at the species level and at a regional scale but, in spite of several empirical tests in the fossil record, it has thus far remained unsupported by empirical evidence. In order to test it conclusively, one has to analyze not only the pattern of species number through time but also its relationship to speciation and species extinction rates; independent evidence for perturbations must also be available.
3. The concept of evolutionary equilibrium at the global scale must be extrapolated over higher levels of taxonomic hierarchy, for reliable species-level data are unavailable at this scale. A theoretical justification for this concept cannot, then, be derived from the theory of island biogeography.
4. The rates of family extinction and origination in the Phanerozoic show no evidence for diversity-dependence, which undermines most quantitative models of biotic diversification based on the concept of global evolutionary equilibrium. Rigorous testing of these models cannot be done at the present state of knowledge because of the uncertainty about the empirical pattern (sampling and taxonomic biases, absolute time scale). 相似文献
2. This concept is theoretically plausible at the species level and at a regional scale but, in spite of several empirical tests in the fossil record, it has thus far remained unsupported by empirical evidence. In order to test it conclusively, one has to analyze not only the pattern of species number through time but also its relationship to speciation and species extinction rates; independent evidence for perturbations must also be available.
3. The concept of evolutionary equilibrium at the global scale must be extrapolated over higher levels of taxonomic hierarchy, for reliable species-level data are unavailable at this scale. A theoretical justification for this concept cannot, then, be derived from the theory of island biogeography.
4. The rates of family extinction and origination in the Phanerozoic show no evidence for diversity-dependence, which undermines most quantitative models of biotic diversification based on the concept of global evolutionary equilibrium. Rigorous testing of these models cannot be done at the present state of knowledge because of the uncertainty about the empirical pattern (sampling and taxonomic biases, absolute time scale). 相似文献
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Elimination of apple stem grooving virus by chemotherapy and development of an immunocapture RT-PCR for rapid sensitive screening 总被引:1,自引:0,他引:1
D. JAMES P A TRYTTEN D J MACKENZIE G H N TOWERS C J FRENCH 《The Annals of applied biology》1997,131(3):459-470
Ombuin (7,4′-dimethyl quercetin) (10 μg ml-1, for 12 wk), glycyrrhizin/quercetin (80 μg ml-1and 10 μg ml-1respectively, for 18 wk), ribavirin (10 μg ml-1, for 12 wk) and quercetin/ribavirin (10 μg ml-1each, for 9–12 wk) reduced the titre of apple stem grooving virus (ASGV) when applied in vitro to infected tissue cultures of Nicotiana occidentalis obliqua Wheeler, and/or Malus domestica. ASGV was not detectable in both plant species after the quercitin/ribavirin treatment when tested by ISEM, herbaceous host indexing, RT-PCR, and immunocapture RT-PCR. A sensitive immunocapture RT-PCR procedure for the detection of ASGV was developed for the screening of treated samples to assess antiviral activity. 相似文献
6.
JAN BERGSTROUM 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1988,21(1):66-66
A. Hoffman & M. H. Nitecki (eds.) 1987: Problematic Fossil Taxa. Oxford Monographs on Geology and Geophysics no. 5. 267 pp. Oxford University Press. ISBN 0–19–503992–0. Price £60 (bound). 相似文献
7.
The Role of Nitrate in the Osmoregulation of Lettuce (Lactuca sativa L.) Grown at Different Light Intensities 总被引:2,自引:0,他引:2
Blom-Zandstra, M. and Lampe, J. E. M., 1985. The role of nitratein the osmoregulation of lettuce (Lactuca sativa L.) grown atdifferent light intensities.J. exp. Bot. 36: 10431052. The effect of different light intensities on the nitrate accumulationvis-à-vis the concentration of other solutes in plantsap expressed from lettuce leaves was studied. After growinglettuce plants under constant environmental conditions for 52d, they were transferred to different light intensities andharvested periodically. A quantitative analysis of componentsin solution in the expressed plant sap showed a decrease innitrate concentration and an increase in the organic acids (mainlymalate) and sugars (mainly glucose) with increasing light intensity.The light intensity only slightly increased the osmolarity ofthe expressed plant sap. The measured osmolarity correspondedvery well with the value estimated from the quantitative analysesimplying that all osmotically active compounds had been accountedfor. The decrease in nitrate concentration in the expressedplant sap was fully compensated for by an increase in the dissociatedorganic acids that partly dissociate twofold to sustain electroneutralityand by an increase in both organic acids and sugars to maintainthe osmolarity. The suggestion is supported that nitrate mayserve as osmoticum at low light conditions to compensate forthe shortage of carbohydrates resulting from suboptimal photosynthesis. Key words: Nitrate accumulation, osmoregulation, Lactuca saliva L. 相似文献
8.
Vibration and sound communication in solitary bees and wasps 总被引:2,自引:0,他引:2
ABSTRACT. Females of solitary bees ( Colletes cunicularius L.) and of digger wasps ( Bembix rostrata L.) produce buzzing sounds and are known to secrete volatile odours when digging their way from the subterranean nests to the soil surface. The odours allow patrolling males to determine the approximate position of the digging virgin female. The buzzes are measured as substrate-borne sound (soil buzz vibrations) and as air-borne sound (soil buzz sounds). Play-back experiments suggest that the soil buzzes are used by the males as additional cues for localization. Faint buzz sounds are emitted regularly by the male during genital contact in copulation. They may serve to change the receptivity of the female. Intense and broadband buzz sounds are produced by bees of either sex, if restrained from moving, perhaps serving to deter predators. 相似文献
9.
REMARKS ON THE APPENDAGES OF TRILOBITES 总被引:1,自引:0,他引:1
JAN BERGSTRÖM 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1969,2(4):395-414
The morphology and function of the exite (the pre-epipodite of Stormer) of the trilobite appendage is discussed. After a review of past work, the morphology is found to be considerably less uniform than previously thought. By an analysis of the morphological variation and by analogy with conditions in recent arthropods, function is thought to have been concerned with different activities such as filtering, swimming, or gill ventilation. Gills may have been present on the ventral side of the body, lateral to the appendages. 相似文献
10.
Male parental care promotes early fledging in an open-nester, the Willow Warbler Phylloscopus trochilus 总被引:1,自引:0,他引:1
The importance of male parental care to female reproductive success was investigated in the monogamous Willow Warbler Phylloscopus trochilus by removing the male parent at two different stages of the breeding cycle. Females that were widowed at the start of egg-laying continued breeding and managed to raise their brood on their own with no apparent reductions in numbers fledged or fledgling body-mass. The widowed females compensated for the loss of male assistance by increasing their own food provisioning rate as compared with control females. However, widows spent less time brooding the small young, and the growth rate of nestlings was reduced. In nests where the male parent was removed 7 days after the eggs hatched, the subsequent growth rate of nestlings was still affected, which suggests that male care is influential throughout the nestling period. On average, broods reared by widows fledged 2 days later than did broods of control females. An extension of the nestling period may appreciably affect reproductive success, since 68% of nests failed due to predation, mostly during the nestling period. We suggest that the main role of male parental care in the Willow Warbler is to assure a high growth rate of nestlings, which leads to early fledging and hence a reduced risk of nest predation. 相似文献