Soil free-living nematodes as bio-indicators for assaying the invasive effect of the alien plant Heterotheca subaxillaris in a coastal dune ecosystem

The Israeli Mediterranean coastal dunes are considered to be a center of floral and faunal speciation and a natural habitat for rare endemic plants, with an extremely sensitive area for alien species invasion. The soil free-living nematode communities are one of the most important groups of soil biota, constituting an essential trophic link between primary decomposers, such as the soil microflora, and larger animals. Despite the fact that soil free-living nematodes play an important role in fundamental ecological processes and are sensitive bio-indicators for understanding processes of succession and nutrient flow in different ecosystems, little is known about the impact of invasive plant species on the soil free-living nematode communities. The present study was designed to fill this gap and evaluate the invasive effect of Heterotheca subaxillaris on the soil free-living nematode communities inhabiting the Mediterranean coastal dunes. Soil samples were collected from the upper (0-10 cm) soil layer under H. subaxillaris (invasive perennial shrub) and Artemisia monosperma (native perennial shrub) at two different sites in the sea-sand ecosystem during the winter and summer seasons. Molecular analysis using the 18S rRNA gene for species determination, along with the traditional method, was a useful tool for evaluation of ecological conditions under the plant associations. The nematode communities, trophic diversity, and taxon composition were affected by the invasive plant at the study sites. Furthermore, this study showed that unfavorable seasonal conditions can also exacerbate the harmful effects of the invasive plants on nematode abundance and trophic and species diversity.