Use of quantitative PCR to detect and differentiate earthworm species

Earthworms are a key component of the soil biology, their abundance and ecological diversity can be used to assess soil biological health. Current assessment of earthworms involves manual hand-sorting individuals from soil before identification. While molecular techniques have been used to describe earthworm diversity, they have not been used to assess earthworm abundance. This study investigates the use of molecular techniques to describe both earthworm abundance and diversity. Quantitative PCR (qPCR) was used to identify the DNA of common pasture earthworms, representing the different ecological groups (e.g. Lumbricus rubellus as epigeic, Aporrectodea caliginosa as endogeic and Aporrectodea longa as anecic). The primers and probes used could specifically identify target earthworm species. The qPCR cycle quantification threshold (Cq) results from dried soil (38 °C) showed improved detection efficiency and stability in comparison to fresh soil. A significant relationship was observed between A. caliginosa Cq value and abundance determined by traditional assessment from soil collected from 129 transects on pasture soils. This study validated the ability of molecular techniques to define earthworm abundance and diversity that will enable the routine assessment of earthworms as biological indicators of soil health. • The abundance of Aporrectodea caliginosa was correlated to qPCR results. • Other earthworm species were also able to be detected from eDNA using qPCR. • The qPCR method was effective using dried soils.