Population age structure of nematodes in the antarctic dry valleys: Perspectives on time, space, and habitat suitability

Patterns of nematode population dynamics in an extreme environment were studies in the McMurdo Dry Valleys of Antarctica. Nematode populations are sensitive to soil disturbance and are useful indicators of environmental change. We hypothesized that the pristine soil environments of Antarctica that are suitable for life would support stable both spatially and temporally nematode populations. We established three sampling sites across an elevation gradient in Taylor Valley and sampled each site at larger and smaller spatial scales three-times over a 6-yr period (1993, 1995, and 1999). Nematode variables and soil moisture were significantly different among years. Soil moisture, nematode abundance, and life cycle parameters varied also with elevation, but not spatial scale at the grid size over the 6 yr. Generally, soil moisture declined during the time of the study and was greatest at the lowest elevation. Throughout the 6 yr, Scottnema lindsavae was most abundant at the highest elevation and dominated all sites, while Eudorylaimus antarcticus was most abundant at the lowest elevation. Plectus antarcticus was present only at the lowest elevation. While Scottnema was negatively correlated with soil moisture, Eudorylaimus and Plectus showed a positive relationship. Similarities among nematode species in life cycle characteristics (e.g., long life cycles and low reproductive rates) may indicate adaptive strategy for survival in the Dry Valleys soil environments. The differences, however, may indicate species specific sensitivity to changes in the soil characteristics such as moisture. Temporal variation of variables describing nematode populations in Antarctic soil suggests the nematode species respond to short-term climate variation and, thus, may be affected by long-term climate change.