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| Parisotoma notabilis (Credit: J. van Duinen) |
Meet Parisotoma notabilis - a tiny fellow that belongs to a group that largely goes unnoticed by most of us. Collembola or Springtails live on our planet already for some 400 Million years and are reputed to be one of the most abundant of all macroscopic animals,
with estimates of 100,000 individuals per cubic meter of topsoil,
essentially everywhere on Earth where soil and related habitats occur.
Most soil springtails are considered beneficial to agriculture. They have the capacity to carry spores of mycorrhizal fungi and mycorrhiza-helper bacteria on their body and thereby help to establish plant-fungal symbioses. They also contribute to controlling plant fungal diseases through their active consumption of mycelia and spores of pathogenic fungi. It even has been suggested that they could be reared to be used for the control of pathogenic fungi in greenhouses and other indoor cultures. Such plans make accurate species delineation indispensable.
Our little friend, P. notabilis has paradoxically been reported to both tolerate and being negatively impacted by industrial pollution, pesticides, and heavy metal. It was also considered a poor indicator for pH, reacting positively to either low or high pH values. This broad range of ecological and
life history parameters raised some doubts about its status as a unique species. This species has been extensively used in numerous studies and was considered well characterized based on its morphology.
Now a new study has a very good explanation for these ambiguous findings. By using DNA Barcoding the researchers were able to postulate that this species likely consists of four species. They could confirm all four lineages by using the nuclear gene 28S and geographical distribution patterns.Their study also included specimens from the type locality which enables them to assign the original species name to one of the lineages. So what has been reported as discordance in response to pollution could just be attributed to the fact that scientists have been looking at several cryptic species.
The result obtained by Porco et al. is certainly what we expect when barcodes are employed for such invertebrates as collembolans. So I expect more to come! I am not so worried about former studies of P. notabilis, they have full validity unless a study included more than one of the lineages. Even then ecological results may have validity as the lineages could have identical response to environmental factors. Actually this is what we see mostly: that disparate species respond in a similar manner to environmental impact. More delicate responses between closely related species would not be detectable anyway for purely statistical reasons.
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