Guide to species selection for tropical and sub-tropical plantations

2d ed. rev

Genetic drift within a protected polymorphism: enigmatic variation in color-morph frequencies in the candy-stripe spider, Enoplognatha ovata

The candy-stripe spider, Enoplognatha ovata, exhibits a striking color polymorphism comprising three morphs. A number of lines of evidence strongly suggest that this polymorphism is maintained by natural selection: its presence in a sister species, E. latimana; the physical nature of the variation; the virtual lack of monomorphic populations; the highly consistent rank-order of morphs within populations; and the presence of large-scale clines associated with climatic variables. However, the absence of selection is equally strongly suggested by very local surveys of morph frequencies over space and time, perturbation experiments, and a variance in morph frequency between populations that is virtually independent of spatial scale. In addition, local spatial patterns in one study site (Nidderdale, Yorkshire, England) have been explained in terms of intermittent drift over half a century ago, a hypothesis supported here by the distributions of four other genetic markers (two allozyme and two visible polymorphisms). A heuristic model is suggested that reconciles these apparently contradictory messages regarding the importance of drift and selection in this system. It is proposed that when allele frequencies of the color morph redimita lie between approximately 0.05 and 0.3, the Δq on q plot is very shallow, so that within this region, where the majority of populations lie, selection is weak and drift is the major force determining local morph frequencies. However, outside this range of frequencies, powerful selection acts to protect the polymorphism. This model may apply to polymorphisms in other species and explain why evidence of selection in natural populations is often elusive

Genetic drift within a protected polymorphism: enigmatic variation in color-morph frequencies in the candy-stripe spider, Enoplognatha ovata

The candy-stripe spider, Enoplognatha ovata, exhibits a striking color polymorphism comprising three morphs. A number of lines of evidence strongly suggest that this polymorphism is maintained by natural selection: its presence in a sister species, E. latimana; the physical nature of the variation; the virtual lack of monomorphic populations; the highly consistent rank-order of morphs within populations; and the presence of large-scale clines associated with climatic variables. However, the absence of selection is equally strongly suggested by very local surveys of morph frequencies over space and time, perturbation experiments, and a variance in morph frequency between populations that is virtually independent of spatial scale. In addition, local spatial patterns in one study site (Nidderdale, Yorkshire, England) have been explained in terms of intermittent drift over half a century ago, a hypothesis supported here by the distributions of four other genetic markers (two allozyme and two visible polymorphisms). A heuristic model is suggested that reconciles these apparently contradictory messages regarding the importance of drift and selection in this system. It is proposed that when allele frequencies of the color morph redimita lie between approximately 0.05 and 0.3, the Δq on q plot is very shallow, so that within this region, where the majority of populations lie, selection is weak and drift is the major force determining local morph frequencies. However, outside this range of frequencies, powerful selection acts to protect the polymorphism. This model may apply to polymorphisms in other species and explain why evidence of selection in natural populations is often elusive

The influence of control motivation on social cognition

SIGLEAvailable from British Library Lending Division - LD:D54966/85 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

A guide to species selection for tropical and sub-tropical plantations

The aim of this publication is to assist foresters in the selection of species for inclusion in the initial phase of forest species trials programmes. The intention is not to recommend particular species for specific site or climatic conditions, or plantation objectives. Given the varying tolerance and adaptability of different species, and the imprecise methods of quantifying site factors and their interactions, such final selection can only be based on first hand experience of species' performance under any given set of site conditions. Such experience can only be gained by the establishment of species trials. Whilst the degree of sophistication and duration of trials programmes may vary, the need for some form of trials before embarking on large scale planting programmes cannot be overemphasized...</p

Cost behaviour of Chinese state-owned manufacturing enterprises during the reform period, 1979-87

SIGLEGBUnited Kingdo

A classification system for nurses work methods

SIGLEGBUnited Kingdo