Identification of Earthworm Species on Golf Course Turf in Arkansas and Oklahoma.

Relatively little research has been conducted on earthworm species composition in U.S. turfgrass systems, and what research has been done primarily focuses on non-native Asian and European species, if the species are listed at all. Preliminary observations at the University of Arkansas Agricultural Research and Extension Station suggested that the species present might belong to the North American-native Diplocardia genus. As morphological identification is difficult on the small Diplocardia spp. and nearly impossible on most juvenile earthworm species, DNA sequencing was used in this study to determine earthworm species composition of earthworms collected from golf course turfgrass systems in Arkansas and Oklahoma.

A study was conducted to identify earthworms collected from golf courses in the Arkansas-Oklahoma region of the transition zone.

Earthworm samples were collected through the dig-and-sort method. DNA analysis was conducted to identify earthworm species using a 710-bp fragment of the the COI protein-coding gene. A formalin-fixed protocol was also tested to determine if DNA from formalin-fixed earthworms could be extracted, amplified, and sequenced.

Preliminary results suggest that DNA amplification was not successful on formalin-fixed earthworms. Additionally, based on analysis of an unrooted Neighbor-Joining tree, ethanol-preserved earthworms from the sampling locations seem to be related to some Diplocardia spp. and various other earthworm species previously reported to be present in Arkansas and Oklahoma in areas outside of the sampling locations from this study.

Ongoing research is looking into morphological identification of formalin-fixed earthworm samples as well as biomass and diversity measurements for each sampling location. Phylogenetic analysis will also be explored further using bootstrapping and the input of additional earthworm sequences.