摘要:

A description is given of some of the demographic parameters for three populations of dandelions, one in an upland grassland (300 m) two in a lowland roadside verge (1 m). These latter populations differed in the density of dandelions found per square metre. All three populations were stable during the observational period, but differed greatly in the parameters that combined to give this stability. The chance of a seed producing seedling in the uplands was greater (x 23) than in the lowlands. The fecundity of plants in the lowland site was between 50 and 100 times greater than that in the uplands. Seed production in the lowlands was dominated by a few large plants. This was not the case in the uplands. The population turnover time was longest in the lowland high density site (20.5 years) and shortest in the upland site (15 years).

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00743.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Methods are described for the visualization of 20 enzymes from the house sparrow,Passer domesticus,in starch gels and by iso‐electric focussing. Many of the methods are applicable to other avian species. Two samples of sparrows from the east midlands of England have been analysed. The patterns that are manifest in the gels can be ascribed to between 33 and 35 loci, of which the same nine are polymorphic in both samples. The level of heterozygosity in these birds is about 15%, which at first sight is higher than an introduced population in Australia. However, this difference disappears when homologous loci are compare

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00744.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

For six years samples of the satyrine butterflyManiolajurtinaL. were collected on small islands in southern Sweden and scored for beak marks, i.e. damage on wings presumably resulting from attacks by birds; in the present study area mainly Red‐backed ShrikeLanius collurioL. An overall mean of 8% (5–1496 in different years) of the females and 1396 (10–2296) of the males had beak marks. Both sexes ofM. jurtinashow variation in spot‐number on the hindwings and there is some evidence that in some years the frequencies of different spot‐number phenotypes with beak marks differ significantly from randomness. Although it is not known how beak mark frequencies are related to predation pressure (reflecting rates of predation or escapes?) it is suggested that, due to behavioural differences of spot‐number phenotypes, birds act as a selective factor influencing the spot‐number variation. The results are discussed in relation to a recent model proposed by Brakefield attempting to account for variation in spot‐numb

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00745.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The three species of green geckos(Phelsuma)on the granitic Seychelles can be identified by colour pattern, snout shape and the occurrence of keeled belly scales. There is no difference in chromosome number (2n=S6) between species but multivariate morphometries analysis, based on body proportions and scalation, can distinguish between the species on Praslin Island.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00746.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The ability of threeDrosophilaspecies;Drosophila obscura, D. subobscuraandD. phalerata,to utilize a range of naturally occurring yeasts as food sources was determined. The yeasts used were the dominant species of two commonly used breeding sites,Sorbus aucupariafruits and the fruiting bodies of the fungusPhallus impudicus.The range of yeast species used was found to reflect the degree ot substrate specialization exhibited by these three species, withD. subobscurabeing broader niched than the other two species. There was an indication thatD. phaleratawas adapted to those yeasts normally found on its natural breeding site,Phallus impudicus.Many factors were found to affect the nutritional adequacy of the yeasts, including their growth period, the larval density, the presence of competitors and particularly the chemical composition of the basal growth medium.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00747.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The question of“how a self‐fertile hermaphrodite will distribute the resources that it allocates to reproduction is studied by means of the ESS approach. Different models of the relations between allocation to male function, the male and female fertilities, and the selfing rate, yield different conclusions about how much resource should be allocated to male function. Values below a half are obtained with one model, while another can give values greater than a half. Even with no selfing, values other than a half are usually obtained; with both models studied, the values decrease with increasing selling. If the selfing rate is assumed to be independent of the fraction of resources allocated to male function, it can be shown that the ESS allocation to male function always decreases as selling increases. The types of relations that might be expected in species with different types of breeding biology, and some data on allocation to male function, are reviewed.The implications for the fitness of male‐ and female‐sterility mutations are discussed. It is argued that the concavity or convexity of the curve relating female fertility to male fertility is not a good guide to when hermaphroditism should exist when there is some selfing. Even with a concave relation, male‐sterility mutants can have a higher fitness than hermaphrodites, if there is some selling and inbreeding depression. Also, when the selfing rate depends on allocation to male I unction, an hermaphrodite ESS does not always exist when the function is concave (as it does when there is no selfing), and such an ESS may exist when the relation is convex. The fitness of male‐ or female‐sterility mutants may also depend on the existence of ‘fixed costs’. It is shown that these do not ailed the ESS alloca

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00748.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Seed populations of white clover polymorphic for the presence/absence of both ovariogenic glucosides and the hydrolysing enzyme linamarase, were introduced into three natural populations. Over the first six months of life a significant increase in the frequency of linamarase containing individuals occurred. Estimated selection coefficients against plants lacking linamarase were in the region of 0.3. This result may have been due to selection at the enzyme locus alone, or to selection favouring cyanogenic individuals which possess both cyanogenic glucosides and enzyme.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00749.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Book reviewed in this article:Island ecology (Outline studies in ecology), by M. GormanComparative Morphology of Recent Crustacea, by Patsy A. McLaughlin. W. H. FreemanGenetic Models of Sexual Selection, by Peter O'DonaldPulmonates, edited by Vera Fretter and J. PeakeWeeds (2nd Edition), by W. C. MuenscherOrang‐Utan Behavior, by T. L. MapleAquatic Oligochaete Biology, edited by R. O. Brinkhurst&D. G. CookStudies in Mathematical Biology, Part II: Populations and Communities, edited by S. A. LevinAtlas of the Netherlands Flora. I, Extinct and very rare species, edited by J. Mennema, A. J. Quene‐Botorenbrood&C. L. Plate. Dr W.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00750.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb00743a.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY