摘要:

To test our hypothesis that gene flow has the potential to prevent genetic isolation of crib populations separated by several kilometres, we caught and marked 137 house mice leaving six cribs being emptied of corn. In an attempt to recapture the mice, we set traps just after crib emptying and again, where feasible, 1–2 months later, in areas surrounding cribs (trap‐nights/trap‐area in hectares:cultivated fields, 3834/29.4; non‐cultivated areas, 2238/4). Additional trapping was carried out near nine empty cribs and in eight cultivated fields (3304 trap‐nights, 17.7 ha trap‐area), each more than 120 m from cribs. After the six cribs were emptied, we recaptured 11% of the crib mice (distance from the crib:mean 81 m, range 0–570 m). In refuge habitats, away from cribs, a breeding population existed and three crib females bred there after emptying of cribs. In demonstrating long dispersal distances and breeding populations away from cribs, our data support the hypothesis that gene flow is potentially large enough to prevent genetic isolation of crib populations separated by expanses of cultivated and uncultivated terrain. The influence of decreased recruitment on gene migration is unclear. Potential predators on nestlings, such as Norway rats, deermice, shrews and voles, escaped from and were trapped

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01823.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The general matching of shell colours to background colours seen in terrestrial gastropods implies that, as in insects, visual predation is an important factor which has a long term directional effect. Polymorphism in snails is associated with background heterogeneity, but the causal relation of polymorphism to heterogeneity is not obvious. Predation could maintain polymorphism if predators are frequency dependent in their choice of prey. However, the appropriate predator behaviour does not depend directly on background heterogeneity. An indirect contribution could be that the heterogeneity serves to lower the signal:noise ratio during the predation process. Background heterogeneity could have a direct effect if the background provided specific elements mimicked by the morphs. The remaining diversity could aid the process by lowering the signal:noise ratio. Polymorphism could be maintained if there was frequency‐dependent niche selection on the part of prey. Background diversity would then be directly involved. It is necessary that there should be independent control of numbers in the different niches. In warm conditions the niche selection could come about because darker morphs, which gain more radiant heat than paler ones, will move to more cryptic sites by seeking the shade. For morph frequences to approach equilibrium values closely it is necessary for the alleles controlling the polymorphism to exhibit dominance. Differences in received energy could make pale morphs disadvantageous compared with dark ones at low temperatures but advantageous at high ones. In spatially varied temperature conditions a polymorphism could be generated without predation. Density‐dependent selection is again requi

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01824.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Three species of littorinid snail live on mangroves of the genusRhizophoraon the north coast of Papua New Guinea. They have recently been placed in the genus Littoraria. The species areL. scabraandL. intermedia, which are monomorphic and cryptic and live on bark, andL. pallescenswhich is polymorphic and lives in foliage.Littoraria intermediawas found mostly on mangroves facing on to partially fresh water, while L. scabra occurred only at sites facing on to the sea;L. pallescensoccurs at both types of site. When kept together in plastic containers,L. pallescensshows a greater propensity to climb than the other two species. The morphs ofL. pallescensare principally yellow, orange or dark. Orange is present at a frequency of 0–9% and yellow at 10–50%. There is little evidence of geographical variation in frequency over 80 km of coast, although one central locality has a significantly higher frequency of yellow than sites to the north or south of it. Throughout the tropics where the species occurs, orange is the rarest and yellow usually the next rarest morph. Larger individuals are on average higher in the foliage than smaller ones, and there is a higher frequency of yellows among larger shells than smaller ones. As the air temperature increases, a progressively larger fraction of a sample was found to be on the under‐surfaces of leaves rather than on the upper epidermis or on flower or leaf buds. When over 30% of a sample is situated on lower surfaces there is a significant excess of yellows and a deficiency of darks on the upper surfaces. This indicates that individuals selectively take up different positions depending on morph colour, resulting in a degree of optimal background matching. Such a choice of location may be of direct relevance to the maintenance of the polymorphism. A difference in morph frequency between the same sites examined in 1979 and 1984 is interpreted as being a result of site select

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01825.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Both Lake Malawi and Lake Victoria have many species of offshore demersal cichlids, most of which are stenotopic. In Lake Tanganyika there are fewer, more eurytopic, demersal species. These differences may be the effect of the physical regimes of the lakes. In Lake Victoria there is no permanent anoxic layer. In both the other lakes, water below 250 m depth is permanently anoxic and the seasonal cycle is dominated by upwelling. In Lake Malawi this is mainly derived from intermediate water containing free oxygen. In Lake Tanganyika upwelling involves hypolimnetic water, which may rise to within 80 m of the surface, causing great short‐term changes in oxygen concentration over the depth range 50–250 m. This has inhibited the development of deep water species restricted to narrow depth ran

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01826.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Experiments on pollen flow and seed production were performed in populations of P. vulgaris in order to examine the roles of selection for reduced self‐pollination in a partially self‐fertile morph, selection for reduced stigma clogging, selection for a pollen saving effect, and selection for disassortative pollination in the evolution of morphological distyly (reciprocal herkogamy). Selection for reduced self‐pollination and disassortative pollination were shown to have a plausible role in the evolution of this dimorphism. Selection for reduced stigma clogging and pollen saving appeared to have no obvious role in the evolution of morphological di

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01827.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

We tested in the laboratory three pairs of species belonging to three genera and families of marine gastropods,Monodonta turbinata, M. turbiformis (Trochidae), Littorina punctata, L. neritoides(Littorinidae),Cerithium scabridum, C. rupestre(Cerithiidae), for resistance to diverse inorganic (heavy metals and NaC1) and organic (detergents and crude oil) pollutants. Each pair consisted of one narrow‐niche species with low genetic diversity and one broad‐niche species with higher genetic diversity. Evidence is presented that in all three cases the species with a higher level of genetic diversity was more resistant to all pollutants than its counterpart. These results suggest that fitness is positively correlated with heterozygosity and support the niche‐width‐variation hypothesis in regard to pollutants. The results also have practical implications for the identification of optimum marine species as genetic monitors of po

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01828.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Samples of mating and non‐mating animals from a natural population of the estuarine isopod Sphaeroma rugicauda showed no evidence of assortative mating or sexual selection for the three genotypes at the phosphoglucose isomerase locu

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01829.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Book reviewed in this article:The North American Grasshoppers:Volume II Acrididae, Oedipodinae, by D. Otte.Animal Behavior and ils Applicaiions,by Derek V. Ellis.Bracken:Ecology, Land Use and Control Technology,edited by R. T. Smith and J. A. Taylor.Functional Vertebrate Morphology,edited by M. Hildebrand, D. M. Bramble, K. F. Liem and D. B. Wake.Air Pollution by Pholochemical Oxidants,edited by R. Guderian.Physiological Ecology of Lichens (Cambridge Studies in Ecology),by Kenneth A. Kershaw.The Evolutionary Ecology of Ant‐Plant mutualisms, by A. J. Beattie.Fundamentals of Insect Physiology,edited by Murray S. Blum.The Leajhppers and Planthoppers,edited by L. R. Nault and J. G. Rodrigue

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01830.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY