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Invasive species are organisms moved from one region to another by humans. Although they are not always harmful to the recipient community, their lack of evolutionary history with their new community can set the stage for destruction. In a world of increasing interconnectivity and warming waters, we expect invasive species will continue to be introduced and that their ranges will expand as more areas become suitable habitats. At this critical point in our planet’s natural history, the need to understand where invasive species can survive and how to detect them are important. Here, I begin with a review of invasive species physiology measurements using species identified as invasive through the Marine Invader Monitoring and Information Collaborative. These data points highlight inconsistencies in measurement technique as well as the importance that acclimation temperature and life stage play on thermal thresholds. Based on the noise in the data, I recommend laboratory experiments to understand the absolute maximum and minimum survivable temperatures for each species, followed by field observations of temperatures needed to grow and reproduce. Then, using a newer invader to Maine Hemigrapsus sanguineus, I measured thermal thresholds for summer and winter-acclimated crabs and found shifts in thermal thresholds as well as evidence that winter temperatures are stressful for these crabs. Lastly, to effectively detect invasive species early, I tested and designed assays for environmental DNA (eDNA) detection of 9 invasive or nuisance species in the Gulf of Maine. Using laboratory experiments and a two-year time series in a local tide pool, I found that not all of the studied invertebrate species can be detected equally. Some organisms with soft, exposed tissues shed eDNA consistently with their abundance, while organisms with exoskeletons or shells do not. This trend does not hold true for all of the studied taxa, but this premise alongside an understanding of natural history and morphology helps clarify the observed trends. Thus, eDNA techniques should not be applied equally across all taxa for management purposes without a clear understanding of the message of the signal. Overall, I made recommendations to better predict suitable habitats for invasive species, characterized thresholds for an understudied invasive species in New England, and continued building upon the challenges of detecting invertebrates with eDNA.
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Challenges in eDNA detection of the invasive European green crab, Carcinus maenas
Abstract The early detection of invasive species is essential to cease the spread of the species before it can cause irreversible damage to the environment. The analysis of environmental DNA (eDNA) has emerged as a non-harmful method to detect the presence of a species before visual detection and is a promising approach to monitor invasive species. Few studies have investigated the use of eDNA for arthropods, as their exoskeleton is expected to limit the release of eDNA into the environment. We tested published primers for the invasive European green crab, Carcinus maenas , in the Gulf of Maine and found them not species-specific enough for reliable use outside of the area for which they were designed for. We then designed new primers, tested them against a broad range of local faunal species, and validated these primers in a field study. We demonstrate that eDNA analyses can be used for crustaceans with an exoskeleton and suggest that primers and probe sequences must be tested on local fauna at each location of use to ensure no positive amplification of these other species.
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- Award ID(s):
- 1849227
- PAR ID:
- 10403971
- Date Published:
- Journal Name:
- Biological Invasions
- Volume:
- 24
- Issue:
- 6
- ISSN:
- 1387-3547
- Page Range / eLocation ID:
- 1881 to 1894
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Background Environmental DNA (eDNA) is an effective tool for the detection and monitoring of presence or absence of rare and invasive species. These techniques have been extended to quantify biomass in vertebrates, particularly in fish species. However, the efficacy of eDNA techniques to quantify biomass in invertebrate species has rarely been examined. This study tested whether eDNA could be used to determine the biomass of the world-wide invasive green crab, Carcinus maena s. In a controlled laboratory study, the relationship between biomass and C. maenas eDNA concentration was examined in the context of different biotic (activity) and abiotic (temperature) parameters. Results When incubating different numbers of crabs in sterile saltwater for up to 7 days, a relationship between eDNA concentration and biomass was observed at temperatures of 6.7 ℃ and 18.7 ℃, but not at 12.8 ℃. Additionally, motor activity, aggression level, time of sampling, and features of organismal decay had significant impact on the concentration of C. maenas eDNA collected. Conclusions We show that eDNA concentration did not correlate with biomass, and that biomass, temperature, organismal characteristics, and potentially many more parameters affect shedding and degradation rates for eDNA in this species, thus, impacting the recoverable eDNA concentration. Therefore, eDNA techniques are not likely to provide a reliable signal of biomass in the invasive invertebrate species C. maenas.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1007/s10530-022-02757-y
