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As global temperatures continue to rise, accurate predicted species distribution models will be important for forecasting the movement of range-shifting species. These predictions rely on measurements of organismal thermal tolerance, which can be measured using classical threshold concepts such as Arrhenius break temperatures and critical thermal temperatures, or through ecologically relevant measurements such as the temperature at which reproduction and growth occur. Many species, including invasive species, exhibit thermal plasticity, so these thresholds may change based on ambient temperature, life stage, and measurement techniques. Here, we review thermal thresholds for 15 invertebrate species invasive to the Gulf of Maine. The high degree of variability within a species and between applied conceptual frameworks suggests that modeling the future distribution of these species in all ecosystems, but especially in the rapidly warming northwest Atlantic and Gulf of Maine, will be challenging. While each of these measurement techniques is valid, we suggest contextualization and integration of threshold measurements for accurate modeling.
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Pushing the Boundaries: Investigating Physiological Limits of Invasive Species and Edna Detection Methods
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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- Award ID(s):
- 1849227
- PAR ID:
- 10586436
- Publisher / Repository:
- University of Maine Electronic Theses and Dissertations
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract BackgroundEnvironmental 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 maenas. In a controlled laboratory study, the relationship between biomass andC. maenaseDNA concentration was examined in the context of different biotic (activity) and abiotic (temperature) parameters. ResultsWhen 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 ofC. maenaseDNA collected. ConclusionsWe 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 speciesC. maenas.more » « less
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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.more » « less
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Abstract Anthropogenic global warming and deforestation are significant drivers of the global biodiversity crisis. Ectothermic and viviparous animals are especially vulnerable since high environmental temperatures can impair embryonic development, but we lack knowledge about these effects upon Neotropical organisms. Here, we estimate how much of the current area with suitable habitats overlaps with protected areas and model the combined effects of climate change and deforestation on the geographic distribution of the viviparous Neotropical lizardNotomabuya frenata(Scincidae). This species ranges in Brazil, Argentina, Paraguay, and Bolivia. We use environmental and physiological variables (locomotor performance and hours of activity) to predict suitable present and future areas, considering different scenarios of greenhouse gas emissions and deforestation. The most critical predictors of habitat suitability were isothermality (i.e., the ratio between mean diurnal temperature range and annual temperature range), precipitation during winter, and hours of activity under lower thermal extremes. Still, our models predict a contraction of suitable habitats in all future scenarios and the displacement of these areas towards eastern South America. In addition, protected areas are not enough to ensure suitable habitats for this species. Our findings highlight the vulnerability of tropical and viviparous ectotherms and suggest that even widely distributed species, such asN. frenata, may have their conservation compromised shortly due to the low representativeness of their suitable habitats in protected areas combined with the synergistic effects of climate change and deforestation. We stress the need for decision‐makers to consider the impact of range shifts in creating protected areas and managing endangered species.more » « less
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Accepted Manuscript1.0
- Dissertation:
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