Nematode dynamics in an African dolomite cave: What is the role of environmental filtering in spatial and temporal distribution?

Abstract

Caves present unique and interesting habitats, captivating scientists in discovering new species and disentangling unfamiliar food webs. However, cave-dwelling nematodes remain poorly studied with minimal evidence supporting their ecological relevance. Therefore, the present study was aimed at investigating the role of selected environmental filters over temporal (seasonal) and spatial (site location) scales on the community dynamics and functional diversity of cave-dwelling nematodes in Dripkelder Cave (South Africa). Multiple sampling sites, with varying levels of exposure to surface material, were investigated over four consecutive seasons. Selected microhabitat characteristics were also measured including sediment respiration, organic and active carbon, moisture content, pH, electrical conductivity, texture, and temperature. The results indicated significant effects on nematode community dynamics from exposure to surface material and environmental filters (including a physical restriction between the entrance area and deeper cave sites). Furthermore, clear temporal trends evidenced the effect of seasonality. An example of this was the rapid response of nematode colonisers (Rhabditis sp.) to the introduction of food and later transitioning to dauer larvae. Finally, multiple trophic groups associated with more isolated cave habitats indicated the potential role of nematode functional diversity in food web dynamics. This study showed that nematode dynamics in caves are likely more complex than originally believed.