Rebecca WangerFollow

Date of Award

2025

Document Type

Honors Thesis (Open Access)

Department

Colby College. Environmental Studies Program

Advisor(s)

Justin Becknell

Second Advisor

Denise Bruesewitz

Third Advisor

David Angelini

Abstract

Jumping worms of the Megascolecidae family are invasive earthworms from East Asia that have been spreading across the United States since the late 1800s (Chang et al., 2021). Recently, the earthworms have gained more attention for their expansion into northeastern states, as they are believed to have negative impacts on the soil biogeochemistry, flora, and fauna of these forest ecosystems that have had no native earthworms given the recent nature of the Last Glacial Maximum (~11,000 yrs ago; Bohlen et al. 2004; McCay et al. 2020). The earthworms are distinguished by their thrashing behaviors, milky-white smooth clitellum, and evenly spaced setae (Chang et al. 2016). But, to identify the worms by species, male genital pores are needed, requiring sampling of the worms when they are adults in the late summer and early fall (McCay et al. 2020; Chang et al. 2021). However, detecting the worms by species is also difficult because many individuals have degraded or absent male genital pores, meaning that genetic detection of the earthworms using soil eDNA could be effective in determining species presence quicker and year-round (McCay et al. 2020). While the method shows promise, little research has been done using soil eDNA earthworm identification with jumping worms in the United States, and none have occurred in Maine (Bienert et al. 2012; Kirse et al. 2021; Lilja et al. 2023).

The goal of our study was to identify the spread of jumping worms using soil eDNA metabarcoding across Maine’s forests and to identify any differences in soil chemistry or plant composition between plots with and without detected worms. To answer our research questions, we collected and analyzed soil chemistry, plant composition, and soil eDNA data from 56 plots across 16 sites in protected forests in Maine (arboretums, land trusts, state parks, botanical gardens, public reserved lands). The eDNA was amplified using COI primers and run on gels using Agar Gel Electrophoresis. Bands were isolated, purified, and sequenced using Oxford Nanopore Sequencing. We used Geneious Prime to bioinformatically detect species and R to investigate potential trends.

In the end, we found no jumping worms, but we did find European earthworms in 20 out of the 36 plots where DNA was sequenced. We also found no significant trends between plant composition, soil chemistry, and earthworm detection and species. As an incredibly invasive species that has been seen to alter forest ecosystems and is pushing north, it is vital to continue studying how jumping worms impact northeastern forest ecosystems. Future use of randomized, widespread, long-term genetic data collection on earthworm presence in relationship to ecosystem characteristics could help managers and researchers better understand the impacts of the worms in Maine and where to limit their spread.

Keywords

Jumping Worms, Invasive Earthworms, eDNA, Forest Ecosystems, Plant Community Composition, Soil Chemistry

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