Ecological patterns in soil nematode diversity and community composition along two environmental gradients

Abstract

Nematodes are considered to be the most abundant animals on Earth, playing a significant role in nearly all the worlds ecosystems. Because of their key position as primary and intermediate consumers in soil food webs, assessing the possibility of changes in diversity of nematode community structure is seen of great importance. Trends in diversity and community structure in relation to elevational and time successional gradients have been well documented among a wide range of forms of life, including animals, plants, insects or some larger invertebrates. In recent years, the elevational trends in community structure and diversity of microorganisms have also been discovered, due to advances in extraction and sequencing of environmental DNA. However, so far there has been very little concerted effort to determine how diversity patterns and community structure of soil nematodes vary with these gradients, despite their abundance and important roles in ecosystem processes. The lag in understanding of nematode communities is partially caused by the lack of an efficient way to identify them. Until recently, all ecological studies of nematodes relied on morphological criteria. However, in the past several years, it has become possible to assess biodiversity of soil nematode by bulk physical isolation of the organisms from soil and extraction of their DNA en masse. Massive parallel sequencing of selected marker genes allows taxonomic classification and estimation of diversity and relative abundances. Not only have these molecular-based methods greatly facilitated rapid sampling, they have also revealed a much greater hidden nematode diversity than was suspected from morphological studies. Here, the aim was to set out to conduct a more systematic and representative study focusing on soil nematodes, in relation to two environmental gradients. I found diversity of soil nematode communities will differ along these gradients, showing continuously changing patterns, and total nitrogen concentration in soil is a good predictor of community diversity for these patterns in both elevational gradient and primary successional gradient. Moreover, along these gradients, community structure of soil nematodes differed and produced a clear succession of communities.