Seventy‐seven house mice (Mus domesticus) from the Orkney island of Eday were released on the Isle of May, Firth of Forth in April 1982. The May had a long‐established mouse population, which was effectively homozygous at 71 allozymic loci scored; the Eday population had a heterozygosity at allozymic loci of 5% (80 loci scored) and was homozygous for three pairs of Robertsonian fusions. Introduced alleles at six loci expressed in blood were scored in animals trapped on the May at the beginning and end of the breeding season each year from 1982 to 1988. Hybrids between native and introduced animals were found in all parts of the island six months after the original release. All the introduced alleles survived and increased in frequency, albeit to different extents. There was no clear evidence of natural selection from differential survival of individuals or seasonal fluctuation of allele frequencies, but the change and apparent stabilization of frequencies after about three years (at different levels to both the parental Eday population and in the animals released) implies that some controlling factors must have acted. These results were wholly unexpected. House mouse populations are divided into small demes, apparently with very restricted gene flow between them. The introduced mice on the May may have been successful because the native population had a low variability, but the latter had persisted successfully for over a century and certainly had a normal social structure. The spread of the Eday alleles to stability in the May population destroys the myth that population division inevitably restricts gene flow in house mice, and draws attention to the importance of coadaptation (or ‘genetic architecture’) in maintaining variation and affecting allele frequencies.

The morphogenetic potential of shoot tip explants of black pepper (Piper nigrum) was investigated and an effective multiple-shoot propagation method is described. Various combinations of media, growth regulators and sterilization treatments were compared. Problems with establishment in tissue culture sometimes occurred, probably caused by endogenous pathogens associated with tissue exudates. The best establishment and proliferation of shoot tip explants was obtained on MS medium containing 1.5 mg l(-1) BAP alone; subsequent growth and development of lateral branches was best on media containing 1.5 mg l(-1) BAP plus 3.0 mg l(-1) IBA. Adenine sulphate inhibited the number of explants showing regeneration but increased the number of shoot buds per regenerating explant. Shoots were rooted on a 50% strength medium containing 1mg l(-1) NAA.

With 10 figures in the text)The colonizing ability, catholic habitat utilization and wide distribution of house mice (Mus domesticus, Rutty) are indicators of their ecological resilience. Numerous studies have been made of commensal, caged and free-living mouse populations though few have assessed the relative importance of physiological and genetical components of adaptability in a simple ecosystem. This paper reports such findings, derived from live-trapping which formed part of an inter-disciplinary study of adaptability in a feral population of house mice living on a small Scottish island (57 ha).The population size ranged from 450-3250 animals. A high proportion of mice showed homerange tenacity, though 15-20'Y0 shifted their range during winter. This 'churning' of the population is consistent with the island population forming an effectively panmictic unit rather than fragmented demes. The breeding season, survival of individuals and change in population size related to patterns of gross climatic variation (temperature and rainfall) so that rates of reproduction and survival were lowest in cold, wet conditions.

The survival of a mouse in the wild depends on its reaction to the environment (food, climate, social conditions, cover, disease and predation), and this depends on the condition or ‘vigour’ of the animal itself. In general an animal increases in vigour until adulthood, and then begins to decrease, in House mice, at an age of approximately 100 days. These changes can be described as ageing; they lead to the characteristic U‐shaped mortality curves deduced from life‐tables in a wide variety of mammalian species. Another factor that has to be taken into consideration is genotype, since animals of different genotype may respond differently to environmental stresses. A large number of deaths in wild‐living House mouse populations in Britain are temperature‐dependent. Animals may respond to cold either physiologically or behaviourally, but it is possible to distinguish between winter survivors and non‐survivors with a fair degree of accuracy on the basis of physiological measurements made in the autumn (i.e. before the time of environmental stress). Nevertheless, any general survival model must incorporate environmental, ontogenetic, and genetic factors and their interactions. A simple model is proposed. Animals are not always struggling for existence. They spend most of their time doing nothing in particular. But when they do begin, they spend the greater part of their lives eating (Charles Elton).

Sexual selection arises when genetically different males show heritable differences in reproductive success. Mouse mating behaviour involves both male competition and female choice. In this paper we show that introduced Y-linked DNA markers spread more extensively through a natural population than do genes inherited matrilineally. Differences in mating success between the sexes and among individual males may alter the pattern and rate of gene flow in natural populations. Another interesting possibility is that the success of the introduced Y chromosome may be attributable to so-called 'selfish' traits, such as sex-linked meiotic drive or intra-uterine competition. However, this study provides little unequivocal evidence to support this view. Differential success of introduced versus resident males may have implications for the reintroduction of endangered mammals into residual wild populations.