摘要:

The hypothesis is suggested that resource depression is one important factor behind the observed regular nest spacing of many birds of prey. It predicts that the proportion of evasive prey in the predator's diet should be reflected in the degree of regularity in its nest spacing. The idea is tested on data from 24 raptorial bird populations of 19 species. The proportion of supposed evasive prey (birds and large mammals) in the diet was positively correlated with the degree of regularity in spacing of the nests, considering all populations or species. No such significant correlation was found for the six highly territorial species, whereas the correlation was highly significant for the other 13 species. Thus, the hypothesis seems most applicable to species with widely overlapping home ranges. However, resource depression could be one reason for territoriality.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02030.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Xerospermum intermedium, a fairly common understorey species in the West Malesian lowland dipterocarp forest is androdioecious, with delayed self‐compatibility. It flowers annually, and has an extended flowering period, with individuals flowering somewhat asynchronously, presenting small flowers with minimal visual lures. The flowers are visited by an unrestricted array of apparently imprecise opportunistic feeders, predominated by trigonid bees and butterflies. Most of these visitors exhibit low fidelity and forage opportunistically on numerous competing tree species. Presentation of nectar in alternating rhythms between the male and hermaphrodite trees appears to induce pollinator movement between them. Out of such alternating visits between the sexes, a low level of short‐range inter‐tree pollen transfer by trigonids and butterflies seems to occur. Despite the elaborate system which promotes pollinator movement between the sexes, this species has retained a low level of self‐compatibility. The physical barriers to pollinator movement in the understorey, and high interspecific competition for pollinators by a large number of tree species, appear therefore to make it difficult to maintain an obligate outbreeding system. Hence, androdioecism may be one of the explanations for the survival ofX. inte

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02031.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Four species of radish of the genusRaphanuswere examined by electrophoresis of water soluble proteins. This technique was used to provide information about the degree of genetic differentiation of the species over a range of gene loci coding for various enzymes. These results give genetic distance estimates showing all four radish species to be closely related. From this data a simple dendrogram is constructed to show the possible interrelationships and evolutionary divergence of these species. The domestic radishRaphanus sativusshows the greatest genetic similarity when compared with an Italian population ofR. landra.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02032.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Because plants are sessile and their flowers and fruits are aggregated, plant mimics are less likely to be mistaken for their models than animal mimics which are mobile and dispersed among their models. Therefore, operator species are more likely to be deceived by animal mimics than plant mimics. In addition, the autonomy of plant appendages implies that warning mimicry provides less advantage to plants than to animals because plants suffer less from sampling by naive operators. Therefore, the advantage of warning mimicry is much greater for animals than plants. These reasons may explain why plant mimicry is less common than animal mimicry, based on attraction of rather than avoidance by operator species, and limited to the class of aggressive mimicry.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02033.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Book reviewed in this article:A World Like Our Own—Man and Nature in Madagascar, by Alison Jolly.Vertebrate Limb Regeneration, by H. Wallace.Statistical Methods in Biology, by N. T.J. BaileyConservation and Evolution, by O. H. Frankel&M. E. SouleEvolution in Age‐structured Populationsby B. CharlesworthEssential Biology, by Herbert T. HendricksonFlora Suzakiensis, edited by Biological Laboratory, Imperial HouseholdPhylogenetic Patterns and the Evolutionary Process, by N. Eldredge&J. CracraftExcursion Flora of the British Isles, by A. R. Clapham, T. G. Tutin&E. F. WarburgWhales, by W. N. BonnerLes Chevaux, Fossiles et Actuels, by V. EisenmannFreshwater Snails of Africa and their Medical Importance, by David S. BrownSymbiosis in Cell Evolution, by Lynn MargulisVegetation Dynamics, by J. M

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02034.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1982.tb02030a.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY