TRIAS project shows a-sexual nematodes are capable of fast genetic adaptation to pollution
21 May 2007
Within the TRIAS research framework, Agnieszka Doroszuk has investigated the numbers and development of nematodes in polluted trial fields near Wageningen. Her dissertation describes how nematodes of the species Acrobeloides nanus, although they multiply through asexual eggs, are capable to adapt swiftly to conditions in polluted natural soils. The trial plot with a high copper level and very low pH (acid environment) didn't show less nematodes than the reference plot. Further investigations showed however a lot had happened to the population:
- the growth rate of nematodes in and from polluted soils was much lower than nematodes from and in clean soils
- the generation time (from egg to maturity and the next generation of a-sexually produced eggs) turned out to be considerably longer. Estimates for the number of generations during the last 20 years were only 14 in polluted soils against 132 in unpolluted reference soil.
Tolerance against copper and a very acid environment might well drain the energy resources in a way that the individual development is strongly impaired.
In spite of the low number of generations ánd the lack of sexual reproduction (sexual recombination is considered to be an important driver of genetical adaptation and evolution) nematode populations from a polluted environment proved to be quite adapted: nematodes from unpolluted soils grew markedly slower in polluted soil than did nematodes from populations that had been exposed to pollution for approximately 20 year.
These findings do have practical consequences. Indeed to rule out genetical adaptation as much as possible, clonally propagating species like Daphnia and springtales are favoured as bio-indicator species. Lab results had pointed out before such species might not be as static as assumed. This study has confirmed that under field conditions this is a mechanism that can't be ignored.
source: Dutch daily NRC 19/20 May 2007, Marianne Heselmans on dissertation by Agnieszka Doroszuk