摘要:

The Central American toad,Bufo marinus, has been extensively introduced throughout the Caribbean and Pacific regions and is now one of the most widespread of terrestrial vertebrates. Details, such as the sources and dates of introductions, the number of individuals introduced and the fates of the introduced populations have been documented and are described. The availability of this historical information makes the introductions of great potential value as a series of evolutionary experiments. They can be used to study the way in which allopatric populations diverge genetically and the effects of population bottlenecks of known size on the genetic characteristics of populations, and to examine theories of rapid speciation caused by genetic revolutions associated with founder events.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01645.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Black colobus monkeys (Golobus salanas) in the Douala‐Edea Reserve, a rain‐forest on the coast of Cameroon, have been shown to avoid young and mature leaves of most of the common plants in their habitat and to feed disproportionately heavily on leaves of rare plants. The proportion of leaves in the diet was low compared to most colobines studied, and the monkeys spent over half their feeding time eating seeds. Patterns of food selection were analysed in relation to distribution of nutrients, digestion–inhibitors and toxins in the vegetation.Colobw satanasselect food items that are rich in mineral nutrients and nitrogen and low in content of the general digestion‐inhibitors, lignin and tannin. They achieve this in the following ways: (i) by feeding preferentially on young leaves, which have higher nutrient content and lower contents of digestion‐inhibitors than mature leaves; (ii) by eating those mature leaves with highest nument content relative to content of digestion‐inhibitors; and (iii) by eating seeds, which are sources of readily available energy and which, as an item class, are less rich in digestion‐inhibitors. Seeds at Douala‐Edea appear to contain Ins nitrogen than leaves andC. satanasselects those seeds with highest nitrogen content. It is suggested that seed‐feeding may be facilitated by the ability of the forestomach flora of these ruminant‐like monkeys to detoxify some of the secondary compounds contained in seeds. Avoidance of most unused young and mature leaf items is correlated with a low nutrienudigestion‐inhibitor ratio; avoidance of most unused seeds could be accounted for by their low nitrogen contents. Most items whose avoidance could not be explained in terms of these major constraints on food selection possess secondary compounds likely to be toxic. It is proposed that relative importance of digestion‐inhibitors, low nutrient content and toxins as constraints on food selection by generalist herbivores will vary greatly among forests with different nutrient and secon

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01646.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Insectivorous plants and ant‐fed plants represent the two ways in which plants have evolved to utilize directly nutrients derived from animals. This paper addresses the limitations under which selection acts to favour the evolution of one or the other of these nutrient‐gathering tactics. Both tactics have evolved independently at least six times under similar ecological conditions, indicating that the evolutionary solutions to ecological problems are limited by the historical make‐up of communities and are, to some extent, predictable. Both insectivorous and ant‐fed plants evolve in environments with very low levels of availability of nutrients in the substrate; the primary use of the animal‐food is probably nitrogen; the vast majority of species are perennial, and most species are tropical or subtropical, although some insectivorous genera are primarily temperate.Although these two nutrient‐gathering tactics evolve in response to similar ecological problems, whether plants evolve an insectivorous habit or the ant‐fed habit depends on the growth forms of the plants and the habitats in which they grow. Most insectivorous plants evolve as herbs in wet, sterile soils or in sterile aquatic habitats; ant‐fed plants evolve as epiphytes on trees in open‐canopied habitats. These kinds of animal‐plant interactions are relatively rare because the environments in which they are favoured by sel

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01647.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Allometric relationships between the area of the shell mouth and live body weight are examined in 19 species of British land snails. Within species, the rate of increase of mouth area on weight is usually less than the isometric expectation, in spite of the logarithmic spiral pattern of growth in most species. It is suggested that this deviation is due mainly to changes in density with size. Two species which conform to isometric expectation alter the geometry of the shell as they pow.Between species, the rate of increase in mouth area on weight in adults is much greater than isometric expectation, and the range of mouth areas at standard weight is considerable. These deviations are almost entirely accounted for by differences in shell geometry between large and small species, the former having higher rates of whorl expansion and smaller or non–existent umbilicuses.The range of loading (weight per unit mouth area) on resting adult snails is thus much less than would be expected. It is suggested that large species are limited in the range of possible shell geometries by the need to minimize loading, while in small species other forces such as desiccation and predation may also be important: the range of geometries is generally larger. Observations on ecology and behaviour tend to support these conclusion

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01648.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

book reviewed in this article:Macroevolution. Pattern and Process, by S. M. Stanley.A World List of Mammadian Species, by G. B. Corbet&J. E. Hill.Indole and Biogenetically Related Alkaloids, edited by J. D. Phillipson&M. H. Zenk.Comparative Ecology, by Y. Itô (edited and translated by J. Kikkawa).The I.B.P. Survey of Conservation Sites: an Experimental Study, edited by A. R.Man, the Promising Primate, by Peter J. Wilson.The Pleistocene Mammals of North America, by Bjorn Kurten&Elaine Anderson.British Gardeners, by Miles Hadfield, Robert Harling&Leonie Highton.The Functioning of Freshwater Ecosystms, by E. D. LeCren&R. H. Lowe‐McConnell.I Fiori della Alpiby F. Rasetti.The Oligocene Rodents of North America, by Albert E. Wood.The Fossil Hunters in Search of Ancient Plants, by Henry N. Andrews.Anatomy of the Dicotyledons, Vol. I, by C. R. Metcalfe&L. Cha

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1981.tb01649.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY