Population demography of Australian feral bees (Apis mellifera).

Honey-bees are widespread as feral animals in Australia. Their impact on Australian ecosystems is difficult to assess, but may include competition with native fauna for floral resources or nesting sites, or inadequate or inappropriate pollination of native flora. In this 3-year study we examined the demography of the feral bee population in the riparian woodland of Wyperfeld National Park in north-west Victoria. The population is very large but varied considerably in size (50-150 colonies/km2) during the study period (1992-1995). The expected colony lifespan for an established colony is 6.6 years, that for a founder colony (new swarm), 2.7 years. The population is expected to be stable if each colony produces 0.75 swarms per year, which is less than the number predicted on the basis of other studies (2-3 swarms/colony per year). Therefore, the population has considerable capacity for increase. Most colony deaths occurred in the summer, possibly due to high temperatures and lack of water. Colonies showed considerable spatial aggregation, agreeing with earlier findings. When all colonies were eradicated from two 5-ha sites, the average rate of re-occupation was 15 colonies/km2 per year. Ten swarms of commercial origin were released and were found to have similar survival rates to founder colonies. However, the feral population is self-sustaining, and does not require immigration from the domestic population.

Mitochondrial DNA of the Mauritian macaques (Macaca fascicularis): an example of the founder effect.

Macaque monkeys (Macaca fascicularis) were introduced to the island of Mauritius approximately 400 years ago. This study compares the mitochondrial DNA of macaques on Mauritius with those from Indonesia and the Philippines. The goal is to measure the amount of evolutionary change that has occurred in this isolated population over 400 years, and to address questions regarding the origin of the Mauritian founders. Amplification of the control region of the mitochondrial genome via the polymerase chain reaction yielded an 1800 base pair DNA fragment which was surveyed for variation using restriction endonucleases. Fifty-two macaques were separated into 17 haplotypes by mapping the restriction sites. No haplotypes were shared among the three populations, and only two closely related haplotypes appeared in the Mauritian sample. Nucleotide variation in the mitochondrial DNA in the Mauritian sample was 10-fold less than the Indonesian and Filipino samples. In contrast, allozyme data estimates of genetic diversity on Mauritius are similar to populations from the ancestral range. The evidence of the more severe bottleneck as measured by mitochondrial data may be explained in part by almost exclusive male dispersal in this species, and may support models of founder events in which rapid population growth prevents substantial loss of nuclear variation. The mitochondrial evidence supports the morphologically and historically based hypothesis that the original founders came from Indonesia.

Ecological population genetics: the interface between genes and the environment.

We review recent studies in ecological genetics considering the way genes interact with the environment. Studies on morphological and allozyme polymorphisms continue to highlight problems in identifying selective factors. Selection on allozymes as well as quantitative traits may only occur under specific conditions. Responses to toxins illustrate how adaptive changes can be based on major genes with polygenic modifiers. Analyses of continuous variation in ecologically relevant traits suggest low levels of heritable variation in some natural situations and emphasize the importance of genetic interactions. It is still not clear if adaptive responses in quantitative traits tend to involve major or minor genes. There is some evidence for genetic tradeoffs among environments and life history traits. Low levels of genetic variation, tradeoffs, and gene flow may restrict distributions and habitats occupied by species, but their relative importance remains unclear.

Adenovirus infection retards ribosomal RNA processing.

Eight hours after infection of KB cells with adenovirus type 12, the rate of conversion from the 32S ribosomal RNA (rRNA) precursor to mature 28S and 5.8S rRNA decreased. An additional RNA species was detected, which appears to be novel, on the basis of its estimated size (about 6.5 kilobases) and its high level of radiolabeling early after infection at low multiplicity.

Inhibition of small nuclear RNA synthesis by ultraviolet radiation.

It was reported earlier that the biosynthesis of small nuclear RNAs (snRNAs) (U1, U2, U3, U4, and U5) shows an unexpected great sensitivity to ultraviolet (UV) radiation (254 nm). In this "early" inhibition, snRNA formation is suppressed immediately after exposure to UV light. There is also a second "late" inhibition of snRNA biosynthesis which requires lower doses of UV radiation and 1-2 h of postirradiation cell incubation to develop fully. In the present work we asked which step, within the metabolic pathway leading to the accumulation of newly made snRNA, is affected by UV light. Both for the early and late UV radiation-induced inhibitions: (a) similar results were obtained after pulse labeling or pulse chasing the radiolabel, implying that UV light did not decrease the stability of newly made snRNA; and (b) gel electrophoretic analysis of radiolabeled RNA that had been hybrid selected with cloned snRNA genes showed no accumulation of putative snRNA precursors, suggesting that UV radiation did not block snRNA processing. Instead, when transcription was carried out in isolated nuclei from irradiated cells, the effects of "early" and "late" inhibition were reproduced, indicating that transcription was affected. The early suppression appears to be a separate reaction from the late inhibition, since U1 snRNA transcription in isolated nuclei was inhibited in the absence of postirradiation cell incubation. There is a small fraction of snRNA synthesis that is resistant to high UV light doses (greater than or equal to 870 J/m2) right after irradiation, but is sensitive to lower doses (less than or equal to 36 J/m2) when the cells are incubated for 2 h after irradiation.