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Evidence is accumulating that small RNAs processed from both host genomic sources and exogenous, viral, double stranded RNAs are biologically active in pathways that downregulate translation and increase degradation of specific transcripts in eukaryotic cells. Here, the mechanisms of small RNA production and processing in Drosophila melanogaster are described, and recent evidence that these pathways are involved in a pathogen-specific, systemic innate immune response is summarised. Small interfering RNAs (siRNAs) processed from viral dsRNAs are presented in the cell as templates to enable sequence-specific silencing of complementary viral transcripts in infected insect cells. Further, there is evidence that, as part of the ongoing immunological arms race between host and pathogen, insect viruses have evolved means to disrupt or subvert the host siRNA pathway.
Habitat loss is the leading cause of wildlife decline worldwide. More prevalent than out-right destruction, however, is habitat fragmentation, exhibited especially in tropical regions. Less well studied is the effect of these patchworks of habitats, and the subsequent effect on local invertebrate populations. A small-scale study assessing moth diversity and abundance between forest edges and crop interiors on a shade coffee plantation was conducted in western Jamaica in January 2009. Ornithologists use shade coffee as an example of sustainable agriculture that protects neotropical migratory birds, and shade coffee plantations have been shown to act as a buffer area (“halo”) between fragmented habitats for insects. The patches of vegetation allow moths to disperse between areas without suitable vegetation for host plants. UV black light traps were used at the edge and interior of each site to sample local moth fauna. While there was no significant difference in morphospecies richness or abundance, there was a difference in diversity between sites, with very low overlap. The lack of significance suggests coffee habitat may act as a buffer between less disturbed forest and more disturbed human altered areas, but that some species may be restricted to certain habitats. Many moth species are host specific, and can serve as useful indicators for ecosystem and vegetative health and relative abundances. Studies of insects are important because of this group's extreme species diversity, and further research is necessary for assessing alpha, beta, and gamma diversity in rapidly disappearing forests in Jamaica and across the world's tropical regions.