The application of reproductive technology to endangered species breeding programmes

Captive breeding plays an increasingly important role in species conservation, but special problems are encountered in achieving the ideal of a demographically stable but genetically diverse population. Breeding programmes involving co-operation among a number of centres are now being developed which will overcome some of these difficulties by identifying individual animals, genetic lineages or age cohorts from which to breed. Application of techniques such as artificial insemination, embryo transfer and semen collection and storage, as well as the monitoring of reproductive status will contribute to the success of such programmes. The usefulness of these procedures for various population problems is discussed and criteria for their appropriate implementation within breeding programmes is outlined.     

Extinction risk assessment for birds through quantitative criteria

The system used for classifying species according to their risk of extinction in international Red Lists is currently being revised by the International Union for Conservation of Nature. The proposed system is based around a set of quantitative criteria and aims to provide a more explicit and objective method that can be applied across a wide variety of living forms. The first major application has been in the preparation of a new edition of Birds to Watch , a summary of threatened bird species at a global level, by BirdLife International. An analysis of the classification of bird species in this publication indicates that the proportion of birds thought to be threatened varies across regions from about 14% in New Zealand and 12% in Africa down to only 3% in Europe. There are some significant differences among regions in the kinds of criteria that lead to threatened listing, with continuing or expected declines in numbers or habitat being especially significant in Africa and Europe.     

Seasonal biological variation in some leaf-miner parasites in the genus Achrysocharoides (Hymenoptera, Eulophidae)

ABSTRACT.

• 1 Most Achrysocharoides species and their Phyllonorycter hosts (Lepidoptera, Gracillariidae) have two generations per year in Britain.
• 2 In those species with separate sex broods, peak male emergence tends to be earlier than peak female emergence. This female emergence lag is shorter in the second generation.
• 3 The mean brood size in the second generation is significantly smaller than in the first in A.cilla males and females, A.latreilli females, mixed sex broods of A.atys, and A.carpini females. A.cilla, A.latreilli and A.niveipes generally have a significantly greater proportion of males in the second generation, but A.atys does not.
• 4 There is a shift to killing later instar Phyllonorycter larvae in the second generation, when a much higher percentage parasitism is generally achieved.
• 5 The intergeneration differences in sex ratio and brood size may be explained by a change in oviposition behaviour of females of the first and second generations.

     

The British species of Achrysocharoides (Hymenoptera, Eulophidae)

Abstract. Taxonomic notes and a key are provided for the eleven species of Achrysocharoides found in Britain including A.carpini sp.n. Several forms of undetermined specific status are also described. Two species-groups are erected: the latreillii group and the aty s group. All British species have been reared as parasites only of leaf-mining larval Gracillariidae (Lepidoptera); one brood is here recorded from Caloptilia on Quercus; all other rearings are from Phyllono-rycter species. Parasite—host associations and speciation within the genus are discussed.     

Use and misuse of the IUCN Red List Criteria in projecting climate change impacts on biodiversity

Recent attempts at projecting climate change impacts on biodiversity have used the IUCN Red List Criteria to obtain estimates of extinction rates based on projected range shifts. In these studies, the Criteria are often misapplied, potentially introducing substantial bias and uncertainty. These misapplications include arbitrary changes to temporal and spatial scales; confusion of the spatial variables; and assume a linear relationship between abundance and range area. Using the IUCN Red List Criteria to identify which species are threatened by climate change presents special problems and uncertainties, especially for shorter‐lived species. Responses of most species to future climate change are not understood well enough to estimate extinction risks based solely on climate change scenarios and projections of shifts and/or reductions in range areas. One way to further such understanding would be to analyze the interactions among habitat shifts, landscape structure and demography for a number of species, using a combination of models. Evaluating the patterns in the results might allow the development of guidelines for assigning species to threat categories, based on a combination of life history parameters, characteristics of the landscapes in which they live, and projected range changes.     

Effect of Four Sowing Date Environments on Growth, Development and Yield Potentials of 15 Pearl Millet Cultivars (Pennisetum americanum L Leeke) During Autumn-Winter Seasons in Marin, N.L., Mexico

A study has been undertaken on the growth, development, andyield potentials of 15 pearl millet cultivars showing a largegenetic variability in growth parameters in different sowingenvironments Sowing date had a significant effect on growthstages (GS1, GS2, GS3), thermal units accumulated in respectivegrowth stages, days to flowering, and yield components of thepearl millet cultivars Significant genotype x sowing date interactionswere also observed for the majority of the variables mentioned. A decline in both temperature and length of photopenod oversuccessive sowing dates from July to September had a drasticeffect on phenology and yield potentials of the pearl milletcultivars. Higher grain yield in the July sowing experiment, compared tothose for other sowing dates, could be related to a longer photopenod(> 13 h), higher temperatures, and a significant differencebetween day and night temperatures. Key words: Environment, growth, yield potentials, thermal units, pearl millet     

The role of avian ‘seed predators’ as seed dispersers

Seed dispersal is a central process in plant ecology with consequences for species composition and habitat structure. Some bird species are known to disperse the seeds they ingest, whereas others, termed ‘seed predators’, digest them and apparently play no part in dispersal, but it is not clear if these are discrete strategies or simply the ends of a continuum. We assessed dispersal effectiveness by combining analysis of faecal samples and bird density. The droppings of seed dispersers contained more entire seeds than those of typical seed predators, but over a quarter of the droppings of seed predators contained whole seeds. This effect was further magnified when bird density was taken into account, and was driven largely by one frequent interaction: the Chaffinch Fringilla coelebs, a typical seed predator and the most abundant bird species in the area and dispersed seeds of Leycesteria formosa, a non‐native plant with berry‐like fruits. These results suggest the existence of a continuum between seed predators and seed dispersers.     

Competition, niche specialization and the evolution of brain size in the genus Peromyscus

Previous studies of relative brain size in mammals have suggested an association with complex habitats and with low reproductive rate. In order to examine the causal relationships more thoroughly, a detailed examination of relative brain size variation in the genus Peromyscus was undertaken. Endocranial volumes were used to estimate brain weight for 32 species including 161 subspecies, and relative brain size calculated as the species deviation from the allometric relationship between brain and body size. The intrageneric allometric coefficient was higher than most values previously reported from low taxonomic levels, but intraspecific coefficients were generally lower than this.
Island species, and relict species isolated on mountain tops, which may be ecological 'islands', had consistently small relative brain sizes, but peninsular species were large brained. Among the remaining species there were significant correlations between litter size and relative brain size, and between the number of competitor species and relative brain size. Species with many competitor species have relatively large brains and small litters. It is concluded that the nature of the geographical distribution, the pattern of species formation and habitat complexity all influence relative brain size in existing forms.     

Heat-Induced Changes in Thermosensitivity and Gene Expression during Development

The thermosensitivity of developing embryos of the fresh water snail Lymnaea stagnalis was investigated from the 4-cell stage to the 3-day-old trochophore larva by means of survival curves for 43.6°C. Cleavage stage embryos were extremely thermoresistant as compared with older stages, and thermosensitivity increases during the development.
Pretreatment with a mild heat exposure (10 min at 39°C) did not induce thermotolerance at the 4-cell stage, but it did so in the early gastrula and trochophora. Development of thermotolerance in 1-, 2-, and 3-day-old stages showed an identical kinetic pattern.
After incubation in ³⁵S-methionine one-dimensional gel electrophoresis was carried out with or without preheating. At the 4-cell stage no enhanced synthesis of heat shock proteins was induced by exposure to heat. At stages of 1 day and older heat induced the enhanced synthesis of the heat shock proteins with apparent molecular weights of 38, 65 and 70 kilodaltons. The synthesis of heat shock protein 70 changes during the early development of Lymnaea both in its constitutive level and in its ability to be enhanced by heat treatment.