Parasite clones in the wild

Article Abstract:

In the laboratory, some species of parasites can reproduce sexually, in addition to their typical asexual means of division. In the laboratory, a large number of recombinants (parasites derived from sexual reproduction, with characteristics from each parent) are being produced from infections with parasites that are genetically different from one another. In the wild, there is evidence that sexual reproduction does not occur readily, as there are populations, especially of the parasites that cause leishmaniasis and Chagas disease, that have been the same for many generations and in many different areas of the world, where variation would be expected. Analysis of the species of seven different parasites shows that the naturally occurring populations are clones, derived asexually from a few populations that have survived. Clones that are similar are found in different locations in the world, and have been found in different species of animals, indicating a lack of change. Clones exist now that existed earlier in time, also indicating lack of variation. These findings suggest that the parasites that exist in the wild are derived primarily from certain successful clones. Genetic recombination by sexual reproduction may still occur but it does not significantly affect the populations of clones that develop. More is needed to be known on the epidemiology of these successful clones. (Consumer Summary produced by Reliance Medical Information, Inc.)

Sexual behavior, Parasites, Reproduction (Biology), Reproduction, Reproduction, Asexual, Asexual reproduction

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Bottoms up for the oceans

Article Abstract:

It is now estimated that at least 10 million species of macrofauna inhabit the the world's ocean bottoms. Two researchers, J.F. Grassle and N.J. Maciolek, reached this figure by taking 233 'box core' samples from 1,500 to 2,500 meters deep along a 176-kilometer stretch off the New Jersey and Delaware coasts. This research is important because it suggests the degree of biodiversity prevailing in the sea floor and because the uncertainties that partly undermine this estimate reiterate the lack of knowledge about the deep oceans.

Biological diversity, Ocean bottom, Marine fauna, Marine animals, Marine productivity

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Case studies of extinction

Article Abstract:

Dobson et al. and Case have developed and examined large data sets to identify the general causes of the changes in the distribution of species. The Dobson et al. study examined whether hotspots for endangered species in the US coincide across both animal and plant taxa. Case's study on birds reveals that the volume of local extinctions and immigrations are roughly the same, and that immigration by exotic species is not affected by the high diversity of native species.

Endangered species, Birds, Species diversity, Extinction (Biology), Varieties

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