Overcoming the Challenges of Studying Soil Nematodes: A New Approach with Implications for All (Soil) Organisms

Post provided by Stefan Geisen

(Soil) Nematodes

“…if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes…” (Cobb 1914)

He may have said it more than a century ago but we now, more than ever, realise that Nathan Augustus Cobb was right. Nematodes are by far the most abundant animals soil, freshwater and marine ecosystems. These tiny worms are barely visible to the human eye (if they’re visible at all), hundreds can inhabit a single gram of soil . Their similar shape might lead you to think that they’re all alike, but that’s not the case. More than 25,000 species have been identified and estimates put their entire species diversity in the 100,000s.

Some common nematode species found in most soils. a) Plectus sp; b) Aphelenchus sp; c) Helicotylenchus sp; d) Thonus sp; e) Mononchus sp; © Wageningen University, Laboratory of Nematology, NL; Hanny van Megen

Some common nematode species found in most soils. a) Plectus sp, b) Aphelenchus sp, c) Helicotylenchus sp, d) Thonus sp, e) Mononchus sp. © Wageningen University, Laboratory of Nematology, NL; Hanny van Megen

This taxonomic and functional diversity has boosted nematodes to become useful bioindicators for soil quality. Nematodes perform many different functions in both terrestrial and aquatic ecosystems. These are mainly defined by what they eat:

  • Bacteria/Fungi: Many nematode groups eat bacteria and fungi. They control the population of these organisms and keep them active.
  • Plants: Plant feeders are the unwanted guests in agricultural systems as well as in our gardens. They can destroy entire harvests by piercing into or infiltrating roots.
  • Omnivores/Predators: Many nematode species prey on other smaller organisms including smaller nematodes and control their abundances.
  • Parasites: These species inhabit other larger organisms and can act as biocontrol agents.

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What About Winter? Accounting for the Snow Season When We Simulate Climate Warming

Post provided by Rebecca Sanders-DeMott and Pamela Templer

Processes that occur in winter are a significant component of annual carbon and nutrient cycles. ©Travel Stock Photos

Processes that occur in winter are a significant component of annual carbon and nutrient cycles. ©Travel Stock Photos

The climate is changing throughout the globe with consequences for the biogeochemical processes and ecological relationships that drive ecosystems. Scientists have been conducting manipulative experiments to determine the effect of climate warming on ecosystems for several decades. These experiments allow us to observe ecosystem responses before the climate changes occur and have yielded invaluable insight that has expanded our understanding of the natural world.

There is a wide range of creative approaches to mimicking climate warming that have been used, for example open-topped chambers which passively heat small areas of soil and small stature plants (like the ITEX global network), burying heating cables in the soil to directly increase soil temperatures (e.g. Harvard Forest experiments), infrared heating lamps (like Jasper Ridge), or even large scale chambers that can encompass taller stature plants like trees and actively warm the air (like the SPRUCE experiment). The focus of much of these inquiries has been on changes that occur during the growing season, when biological activity is at its peak. Continue reading

Issue 7.1

Issue 7.1 is now online!

The January issue of Methods is now online!

As always, the first issue of the year is our sample issue. You can access all of the articles online free of charge. No subscription or membership is required!

We have two Open Access articles and two Applications papers in our January issue.

Recognizing False Positives: Environmental DNA (eDNA) is increasingly used for surveillance and detection of species of interest in aquatic and soil samples. A significant risk associated with eDNA methods is potential false-positive results due to laboratory contamination. To minimize and quantify this risk, Chris Wilson et al. designed and validated a set of synthetic oligonucleotides for use as species-specific positive PCR controls for several high-profile aquatic invasive species.

BiMat: An open-source MATLAB package for the study of the structure of bipartite ecological networks. BiMat enables both multiscale analysis of the structure of a bipartite ecological network – spanning global (i.e. entire network) to local (i.e. module-level) scales – and meta-analyses of many bipartite networks simultaneously. The authors have chosen to make this Applications article Open Access.

Gemma Murray et al. provide this month’s second Open Access article. In ‘The effect of genetic structure on molecular dating and tests for temporal signal‘ the authors use simulated data to investigate the performance of several tests of temporal signal, including some recently suggested modifications. The article shows that all of the standard tests of temporal signal are seriously misleading for data where temporal and genetic structures are confounded (i.e. where closely related sequences are more likely to have been sampled at similar times). This is not an artifact of genetic structure or tree shape per se, and can arise even when sequences have measurably evolved during the sampling period.

Our January issue also features articles on Monitoring, Population Ecology, Genetics, Evolution, Community Ecology, Diversity and more. Continue reading