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) 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.

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.

Terrestrial arthropods are abundant and diverse with outsized ecological and economic importance. Our ability to monitor this diversity is hampered by the variety of sampling techniques and taxonomic expertise required to catalog the species in an area. DNA metabarcoding approaches show promise but have mainly been limited to trapping studies where DNA is extracted from captured individuals. Here we illustrate the promise of terrestrial plant surfaces as reservoirs of environmental DNA (eDNA) that is rich in arthropod biodiversity information. We posit that collection of surface eDNA will enable easier and more rapid arthropod inventories. We collected 40 paired samples using two novel terrestrial surface eDNA sampling techniques – ‘roller’ tree bark and ‘spray’ foliage sampling – in a New Jersey, USA pine barrens forest. Metabarcoding using two primer sets (COI and 16S) revealed the presence of 177 arthropod families (from 21 orders), representing 80% of the family-level diversity expected in the area based on accumulation curves. Spray samples revealed more families than roller (148 vs. 126), while the two methods showed distinct, though overlapping, community composition. The two primer sets revealed similar alpha diversity, although they also captured different taxonomic subsets. A more limited comparison of roller and spray sampling with traditional aquatic and soil eDNA samples revealed a greater family diversity in surface samples, especially compared with soil. Our study highlights the value of eDNA metabarcoding surveys for achieving the elusive goal of rapid, cost-effective arthropod inventories, and thus realizing a range of ecological research and management goals.

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