Human-mediated dispersal drives the spread of the spotted lanternfly (Lycorma delicatula).

The spotted lanternfly (Lycorma delicatula) is a novel invasive insect from Asia now established and spreading throughout the United States. This species is of particular concern given its ability to decimate important crops such as grapes, fruit trees, as well as native hardwood trees. Since its initial detection in Berks County, Pennsylvania in 2014, spotted lanternfly infestations have been detected in 130 counties (87 under quarantine) within Connecticut, Delaware, Indiana, Maryland, New Jersey, New York, Ohio, Virginia, and West Virginia. Compounding this invasion is the associated proliferation and widespread distribution of the spotted lanternfly's preferred host plant, the tree-of-heaven (Ailanthus altissima). While alternate host plant species have been observed, the tree-of-heaven which thrives in disturbed and human-dominated areas (e.g., along roads and railways) is likely facilitating the population growth rates of spotted lanternfly. We simulated the population and spread dynamics of the spotted lanternfly throughout the mid-Atlantic USA to help determine areas of risk and inform continued monitoring and control efforts. We tested the prediction that spotted lanternfly spread is driven by human-mediated dispersal using agent-based models that incorporated information on its life-history traits, habitat suitability, and movement and natural dispersal behavior. Overwhelmingly, our results suggest that human-mediated dispersal (e.g., cars, trucks, and trains) is driving the observed spread dynamics and distribution of the spotted lanternfly throughout the eastern USA. Our findings should encourage future surveys to focus on human-mediated dispersal of egg masses and adult spotted lanternflies (e.g., attachment to car or transported substrates) to better monitor and control this economically and ecologically important invasive species.

Assessing the efficacy of eDNA metabarcoding for measuring microbial biodiversity within forest ecosystems.

We investigated the nascent application and efficacy of sampling and sequencing environmental DNA (eDNA) in terrestrial environments using rainwater that filters through the forest canopy and understory vegetation (i.e., throughfall). We demonstrate the utility and potential of this method for measuring microbial communities and forest biodiversity. We collected pure rainwater (open sky) and throughfall, successfully extracted DNA, and generated over 5000 unique amplicon sequence variants. We found that several taxa including Mycoplasma sp., Spirosoma sp., Roseomonas sp., and Lactococcus sp. were present only in throughfall samples. Spiroplasma sp., Methylobacterium sp., Massilia sp., Pantoea sp., and Sphingomonas sp. were found in both types of samples, but more abundantly in throughfall than in rainwater. Throughfall samples contained Gammaproteobacteria that have been previously found to be plant-associated, and may contribute to important functional roles. We illustrate how this novel method can be used for measuring microbial biodiversity in forest ecosystems, foreshadowing the utility for quantifying both prokaryotic and eukaryotic lifeforms. Leveraging these methods will enhance our ability to detect extant species, describe new species, and improve our overall understanding of ecological community dynamics in forest ecosystems.

Differential post-fledging habitat use of Nearctic-Neotropical migratory birds within an urbanized landscape.

BACKGROUND: Persistent declines in migratory songbird populations continue to motivate research exploring contributing factors to inform conservation efforts. Nearctic-Neotropical migratory species' population declines have been linked to habitat loss and reductions in habitat quality due to increasing urbanization in areas used throughout the annual cycle. Despite an increase in the number of studies on post-fledging ecology, generally characterized by the period between fledging and dispersal from natal areas or migration, contextual research linking post-fledging survival and habitat use to anthropogenic factors remains limited. METHODS: Here, we examined habitat use of post-fledging habitat-generalist gray catbirds (Dumetella caroliniensis), and habitat-specialist wood thrushes (Hylocichla mustelina), up to 88 days after fledging within an urbanized landscape. These Neotropical migratory species share many life-history traits, exhibit differential degrees of habitat specialization, and co-occur in urbanized landscapes. Starting from daily movement data, we used time-integrated Brownian bridges to generate probability density functions of each species' probability of occurrence, and home range among 16 land cover classes including roads from the US Geological Survey National Land Cover Database for each species. RESULTS: Habitat use differed between pre- and post-independence periods. After controlling for factors that influence habitat use (i.e., pre- or post-independence period, fate (whether individuals survived or not), and land cover class), we found that wood thrushes occupied home ranges containing six times more forest land cover than catbirds. In contrast, catbirds occupied home ranges containing twice the area of roads compared to wood thrushes. Wood thrushes had greater variance for area used (km2) among land cover classes within home ranges compared to catbirds. However, once fledglings achieved independence from parents, wood thrushes had lower variance associated with area used compared to catbirds. CONCLUSIONS: Our findings support predictions that habitat-generalist gray catbirds spend more time in developed areas, less time in forest habitat, and use areas with more roads than the forest-specialist wood thrush. We found strong effects of pre- and post-independence periods on all of the response variables we tested. Species-specific habitat use patterns will likely be affected by projected increases in urbanization over the next several decades leading to further reductions in available forest habitat and increased road density, and will have important implications for the ecology and conservation of these birds.