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Environmental DNA (eDNA) approaches to monitoring biodiversity in terrestrial environments have largely focused on sampling water bodies, potentially limiting the geographic and taxonomic scope of eDNA investigations. We assessed the performance of two strictly terrestrial eDNA sampling approaches to detect arboreal mammals, a guild with many threatened and poorly studied taxa worldwide, within two central New Jersey (USA) woodlands. We evaluated species detected with metabarcoding using two eDNA collection methods (tree bark vs. soil sampling), and compared the performance of two detection methods (qPCR vs. metabarcoding) within a single species. Our survey, which included 94 sampling events at 21 trees, detected 16 species of mammals, representing over 60% of the diversity expected in the area. More DNA was found for the 8 arboreal versus 8 non-arboreal species detected (mean: 2466 vs. 289 reads/sample). Soil samples revealed a generally similar composition, but a lower diversity, of mammal species. Detection rates for big brown bat were 3.4 × higher for qPCR over metabarcoding, illustrating the enhanced sensitivity of single-species approaches. Our results suggest that sampling eDNA from on and around trees could serve as a useful new monitoring tool for cryptic arboreal mammal communities globally.

Comparison of polychlorinated biphenyl (PCB) concentrations between the sexes of mature fish may reveal important behavioral and physiological differences between the sexes. We determined whole-fish PCB concentrations in 23 female summer flounder Paralichthys dentatus and 27 male summer flounder from New Jersey coastal waters. To investigate the potential for differences in diet or habitat utilization between the sexes, carbon and nitrogen stable isotope ratios were also determined. In 5 of the 23 female summer flounder, PCB concentrations in the somatic tissue and ovaries were determined. In addition, we used bioenergetics modeling to assess the contribution of the growth dilution effect to the observed difference in PCB concentrations between the sexes. Whole-fish PCB concentrations for females and males averaged 87 and 124 ng/g, respectively; thus males were 43% higher in PCB concentration compared with females. Carbon and nitrogen stable isotope ratios did not significantly differ between the sexes, suggesting that diet composition and habitat utilization did not vary between the sexes. Based on PCB determinations in the somatic tissue and ovaries, we predicted that PCB concentration of females would increase by 0.6%, on average, immediately after spawning due to release of eggs. Thus, the change in PCB concentration due to release of eggs did not explain the higher PCB concentrations observed in males. Bioenergetics modeling results indicated that the growth dilution effect could account for males being 19% higher in PCB concentration compared with females. Thus, the bulk of the observed difference in PCB concentrations between the sexes was not explained by growth dilution. We concluded that a higher rate of energy expenditure in males, stemming from greater activity and a greater resting metabolic rate, was most likely the primary driver for the observed difference in PCB concentrations between the sexes.

Environmental DNA (eDNA) has recently emerged as an effective tool for invasive species biosecurity. We explored the use of eDNA for the detection of khapra beetle (Trogoderma granarium, Everts 1898), an invasive insect of cereal grains and other food products that has a high global economic impact. We developed a novel method for aggregating khapra beetle eDNA deposited in stored grain that entails washing a sample of rice, filtering the sample, and detecting trace beetle DNA using a standard qPCR workflow. To explore the performance of this method, we raised 500 khapra beetle larvae within 500 g of rice over a 14‐day period and then removed them. We then used this “spiked” rice to create a range of simulated densities of khapra beetle larvae. This lab approach mimics conditions that are comparable to field densities of ~1.4 to 180 beetles per 50 kg of rice (1/8 to 16 spiked rice grains per 100 g sample of clean rice), assuming DNA is uniformly distributed within the rice. We detected khapra beetle eDNA from all density levels tested. Logistic models revealed that eDNA amounts equivalent to what is left by ~1 khapra beetle larva in a 50 kg container of rice can be detected with 85% to >97% certainty, depending on the number of qPCR technical replicates run per sample. Based on this model, we estimated that for one 50 kg container of rice where beetle DNA is uniformly distributed, a single sample of 100 g with six technical replicates would be sufficient to be >99% certain that the container was free of khapra beetle eDNA (95% credible intervals: 97.7%–100%). Our results suggest that eDNA surveys may be useful as a cost‐effective, first‐step detection of khapra beetle in stored grain and provide a means to map the relative magnitude of khapra beetle transport pathways, informing allocation of conventional biosecurity inspection efforts. Khapra beetle is a agricultural pest posing high global biosecurity risk. We show eDNA sampling of stored grain can detect ~1 khapra beetle larva in a 50 kg container of rice with 85% to >97% certainty (dashed line is 95% certainty level) depending on whether 1 (red) or 3 (blue) qPCR technical replicates are performed. This result suggests, with further exploration, eDNA surveys can become cost‐effective first‐step biosecurity protocol for khapra beetle, or a means to map the relative magnitude of khapra beetle transport pathways.

Terrestrial arthropods are a diverse taxonomic group of significant ecological and economic importance. Our ability to understand the diversity that comprises this group is hampered by the variety of sampling techniques and high level of taxonomic expertise required to identify individual species. DNA metabarcoding approaches have potential to overcome these challenges but have been mainly limited to studies where DNA is directly extracted from trapped individuals. We posit that collection of environmental DNA (eDNA) deposited on vegetation surfaces could provide an alternative method of conducting metabarcoding‐based arthropod inventories. In this study, we illustrate the promise of characterizing arthropod biodiversity based on eDNA collected from terrestrial plant surfaces. We collected 40 paired samples using two novel eDNA sampling techniques—tree bark and foliage sampling—in a New Jersey, USA, pine barrens forest. Metabarcoding using two primer sets revealed significantly higher taxonomic richness for the 16S versus COI primer set (1077 vs. 650 molecular operational taxonomic units; MOTUs), as well as higher richness and diversity in foliage versus bark samples. Accumulation curves suggest that our samples captured about half of the available MOTU‐level diversity. Matching to reference databases revealed 28 arthropod orders, 181 families, 353 genera, and 292 species. Despite having lower MOTU‐level richness, the COI primer set revealed more taxa that were identified to species (197 vs. 115) and genus (227 vs. 173) thanks to a more complete reference database. The two primer sets and sampling substrates showed distinct community compositions that differed in important ecological traits (feeding guild, body size), demonstrating the utility of a multi‐faceted sampling and analytical approach. Our study highlights the value of exploiting eDNA left on plant surfaces via metabarcoding for contributing to rapid arthropod inventories, and thus realizing a range of ecological research and management goals. We collected 40 eDNA samples from tree bark and understory foliage in a New Jersey, USA forest. Metabarcoding with two primer sets revealed over 1000 arthropod MOTUs from which we identified 292 species, 181 families, and 28 orders. Our work provides proof‐of‐concept evidence that surface eDNA surveys of terrestrial arthropod communities are feasible and represent a potentially viable new tool for use in research, management, and restoration.

Environmental DNA surveys have revolutionized monitoring of rare or cryptic species and species inhabiting areas where conventional sampling is difficult or dangerous. Recent advancements within terrestrial environments include the capture of eDNA deposited by animals on surfaces such as tree bark and foliage, hereafter “surface eDNA.” Notably, a technique which uses commercial paint rollers to aggregate surface eDNA has been deployed with success to detect the presence of forest insect pests providing a potentially powerful new management tool. However, before widespread adoption is feasible, the efficiency and logistics of roller sample collection and study design, especially relative to realistic survey conditions, must be evaluated. We compared the performance of two DNA preservation treatments—cold and ethanol—on their ability to reduce the loss of captured eDNA on rollers over time. Additionally, we evaluated how the detection probability of our target species, the spotted lanternfly (Lycorma delicatula), varied with sampling effort (time spent rolling per sample) and the initial quantity of eDNA present. Finally, we evaluated how the number of trees sampled per roller influenced the final concentrations of lanternfly eDNA remaining on the roller. We found storing rollers with ethanol or cold temperatures resulted in 3–10‐fold greater concentrations of experimentally controlled eDNA relative to no treatment after 24 h. Detection probability declined as the amount of lanternfly eDNA decreased, but did not change in response to sampling effort over sample time (10–80 s/tree). Finally, recovered lanternfly eDNA decreased as more trees were sampled by a single roller—a 91% reduction after 7 trees—potentially due to captured DNA being transferred back from the roller onto the bark. Our results provide improved guidance for deploying roller surface eDNA methods for spotted lanternfly surveys, and for invasive insect pest surveillance and monitoring programs generally. Surveying plant surfaces for eDNA is relatively novel. We present several experiments to improve on a recent technique used for surveying bark and branches of trees for insect DNA. Cold temperatures can preserve DNA on paint rollers, used to sample trees, while sampling more than a few trees can lead to DNA loss.

Fundulus grandis (Baird and Girard), the Gulf Killifish, is an abundant species throughout the marshes of the northern Gulf of Mexico. Its wide distribution and high site fidelity makes it an ideal indicator species for brackish and salt marshes, which experience a variety of anthropogenic disturbances. Despite the ecological, commercial, and scientific importance of F. grandis , age determination methods have not been validated and little is known of its growth pattern. By combining a tag-recapture study with a chemical marker to stain otoliths, we validated an ageing method for F. grandis adults (49–128 mm TL) using whole sagittal otoliths and determined growth rates of recaptured individuals in winter ( n  = 58) and summer ( n  = 36) in Louisiana. Mean somatic growth in length was significantly greater during the winter (0.085 mm d −1 ) than summer (0.054 mm d −1 ). In contrast, mean otolith growth was significantly greater in summer (1.37 μm d −1 ) than winter (0.826 μm d −1 ). The uncoupling of somatic and otolith growth may be primarily attributed to warm summer temperatures, which led to enhanced otolith growth while simultaneously reducing somatic growth. Fundulus grandis was aged to a maximum of 2.25 years. The parameters of the von Bertalanffy growth model were estimated as: L ∞  = 87.27 mm, k  = 2.43 year −1 , and t 0  = −0.022. These findings reveal essential age and growth information for F. grandis and provide a benchmark to evaluate responses to environmental disturbances.

The doi for the dataset mentioned in the acknowledgements is incorrectly cited as doi: https://doi.org/10.7266/N7SF2T32. The correct doi for this dataset is https://doi.org/10.7266/N7NZ85M4.

Fundulus grandis, the Gulf Killifish, is an abundant fish species with a widespread distribution throughout the marshes of the Gulf of Mexico. The wide distribution and high site fidelity of this species makes it an ideal indicator species for Gulf of Mexico brackish and salt marshes, which experience a diversity of anthropogenic disturbances. Despite the ecological, commercial, and scientific importance of F. grandis, little is known of its growth pattern, and age determination methods are currently lacking. Age and growth information is essential for understanding baseline growth patterns. By combining a tag-recapture study with a chemical marker to stain otoliths, I validated an ageing method for F. grandis using whole otoliths and determined growth rates of F. grandis in winter (n = 58) and summer (n = 36) in Louisiana. The recapture rates for tagged individuals during winter and summer were 10% and 12%, respectively. Mean somatic growth in length was significantly greater during the winter (0.085 mm per day) than the summer (0.054 mm per day). In contrast, mean otolith growth was significantly greater during the summer (1.37 µm per day) than the winter (0.826 µm per day). The observed uncoupling of somatic and otolith growth is attributed to warm summer temperatures which led to enhanced otolith growth while simultaneously reducing somatic growth. Fundulus grandis were aged to a maximum of 2.25 years. The parameters of the Von Bertalanffy growth model were estimated as: L ∞ = 87.27 mm, k = 2.43 year–1, and t 0 = –0.022. These findings reveal basic age and growth information for F. grandis, demonstrating faster growth and a shorter lifespan than its congener species, Fundulus heteroclitus.

Comparison of polychlorinated biphenyl (PCB) concentrations between the sexes of mature fish may reveal important behavioral and physiological differences between the sexes. We determined whole-fish PCB concentrations in 23 female summer flounder Paralichthys dentatus and 27 male summer flounder from New Jersey coastal waters. To investigate the potential for differences in diet or habitat utilization between the sexes, carbon and nitrogen stable isotope ratios were also determined. In 5 of the 23 female summer flounder, PCB concentrations in the somatic tissue and ovaries were determined. In addition, we used bioenergetics modeling to assess the contribution of the growth dilution effect to the observed difference in PCB concentrations between the sexes. Whole-fish PCB concentrations for females and males averaged 87 and 124 ng/g, respectively; thus males were 43% higher in PCB concentration compared with females. Carbon and nitrogen stable isotope ratios did not significantly differ between the sexes, suggesting that diet composition and habitat utilization did not vary between the sexes. Based on PCB determinations in the somatic tissue and ovaries, we predicted that PCB concentration of females would increase by 0.6%, on average, immediately after spawning due to release of eggs. Thus, the change in PCB concentration due to release of eggs did not explain the higher PCB concentrations observed in males. Bioenergetics modeling results indicated that the growth dilution effect could account for males being 19% higher in PCB concentration compared with females. Thus, the bulk of the observed difference in PCB concentrations between the sexes was not explained by growth dilution. We concluded that a higher rate of energy expenditure in males, stemming from greater activity and a greater resting metabolic rate, was most likely the primary driver for the observed difference in PCB concentrations between the sexes.