摘要:

Global regressions of ecological population densities on body mass for mammals and for terrestrial animals as a whole show that local population energy‐use is approximately independent of adult body mass—over a body mass range spanning more than 11 orders of magnitude. This independence is represented by the slope of the regressions approximating –0.75, the reciprocal of the way that individual metabolic requirements scale with body mass. The pattern still holds for mammalian primary consumers when the data are broken down by geographic area, by broad habitat‐type and by individual community. Slopes for mammalian secondary consumers are also not statistically distinguishable from –0.75. For any given body mass temperate herbivores maintain on average population densities of 1.5 to 2.0 times those of tropical ones, though slopes do not differ. Terrestrial animals of all sizes exhibit approximately the same range of population energy‐use values. These results agree with those reported for population energy‐budgets. It is suggested that rough independence of body mass and the energy‐use of local populations is a widespread rule of animal ecology and comm

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb01990.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Many of the flowers produeed bv a plant fail to mature seeds despite effective pollination. The role of inflorescence architecture governing patterns of abortion in plants has been underestimated. 1 he inflorescence ofEchium vulgareL. comprises a raceme bearing lateral inflorescences, each of which is cymosc. Within each cyme, there is a correlation between the proximity of a flower to the main axis and its order of flowering; and (lie probability of it maturing seeds. These findings appear to result from a decrease in the availability of maternal resources as the flowering period progresses. No relationship could be shown between the position of the cyme on the main inflorescence and the number of seeds set per flower although position was correlated with the length of the cyme, the number of (lowers and the length of the subtending bract. The mctamcric units of E. vulgare appear to function largely independently in their assimilation of resources. Larger cymes not only bear more flowers, but also draw on a larger area of photosynthetic tissue for resources. This hypothesis is supported by the removal of the bract or of part of the cyme at the onset of flowering; cymes without bracts mature fewer ovules than controls while decapitated cymes mature a greater proportion of ovules.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb01991.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The bimodal distribution of shell shape (height: diameter), that is found in various geographically widely separate and taxonomically distinct land snail faunas of many different regions of the world, occurs also in a Mediterranean fauna and in a desert fauna that is derived from it. The desert fauna is, however, closer to the bisector than the Mediterranean one.High‐spired snails are mainly rock‐dwellers, and equidimensional to low‐spired snails are bush‐dwellers or soil‐diggers, with a few rock‐dwellers; litter‐dwellers are small‐sized species that may have either high‐ or low‐spired shells.These results are discussed in adaptive terms. Litter is probably the more primitive of these micro‐environments. Many of the small, litter‐dwelling snails are ovo‐viviparous rather than oviparous, perhaps so as to avoid attacks on the eggs by saprophytic fungi. The shift away from the litter environment is accompanied by a trend to abandon the ovo‐viviparous strategy, in favour of oviparity, the snail using its foot to dig into the soil and lay eggs. The conchometric differences between bush‐, ground‐ and rock‐dwelling snails may perhaps reflect selective pressure to increase the size of the foot; and constraints of a habitat that consists of narrow interspaces between rocky boulders. Snails that habitually dig into the ground during periods of inactivity, and roam over the ground when active, requires a very large foot and, consequently, a very large‐mouthed shell to accommodate it; the result is an equidimensional shell, globose or turbiniform in shape. Snails that climb up vertical vegetation would also require a large foot, and consequently a large‐mouthed shell to contain it. A fully globose shell would however be disadvantageous, since it might cause undesired torque. Hence, bush‐dwellers tend to be flatter than soil‐diggers. Snails that habitually live in rock crevices, and on hard substrata, would not require a very large foot; they would need a narrow shell, both to enable easy manoeuvring through crevices and to reduce torque, the result being a small‐mouthed, usually high‐spired shell.The classification of land snails into bush‐, soil‐ or rock‐dwellers closely follows the taxonomic classification. In those species that depart from the habitat that is typical of their taxonomic group towards anot

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb01992.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The habitat use and diets of small mammals inhabiting grassland plots of different successional ages were investigated by live‐trapping and faecal analysis over a period of 16 months. The contribution of the major plant life forms and the structural profile of the vegetation of each plot and the availability of insect prey were assessed. The dominant species of small mammal found on each plot wereSorex araneus, S. minutus, Apodemus sylvaticusandMicrotus agrestis. Small mammals were most commonly found in the late and mid‐successional stages, reflecting the habitat structure and food availability. A wide range of insects and other invertebrates were eaten by all four species and insects formed 50–62% of the animal prey taken. The incidence of certain prey in the diets differed between plots. The daily consumption rate of invertebrates by shrews and mice was estimated at some 6800 prey per ha. The greatest predatory impact came from shews butA. sylvaticusshowed increased consumption of invertebrates in spring. The combined predatory impact of the grassland small mammal community on insect populations alone was estimated to average 0.01% per day and is predicted to be greatest in the mid‐successional

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb01993.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Sexual dimorphism in parasitoid wasps of the family Ichneumonidae is surveyed and the problems associated with its measurement are discussed. Conclusions drawn by Hurlbutt are demonstrated to be incorrect. The significance of sexual dimorphism in ichneumonids is explored briefly.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1987.tb01994.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY