Asymmetric biotic interactions and abiotic niche differences revealed by a dynamic joint species distribution model

Persistence and recovery of dinotefuran in eastern hemlock (Tsuga canadensis) foliage and twigs by UPLC-MS/MS and ELISA

BACKGROUND

Dinotefuran, a systemic neonicotinoid insecticide, is approved for control of hemlock woolly adelgid (HWA) (Adelges tsugae Annand), an invasive sap-feeding insect that can kill eastern hemlocks (Tsuga canadensis). Dinotefuran is highly water soluble, facilitating more rapid translocation and HWA control than other neonicotinoids, but its persistence is not well-known. Samples of needles and twigs were collected in spring 2021 from 50 hemlocks treated with a dinotefuran basal trunk spray in 2018 or 2019 (131-145 weeks and 85-93 weeks before sampling, respectively). Processed samples were analyzed with ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) and enzyme-linked immunosorbent assays (ELISA).

RESULTS

Dinotefuran residues were 4.6-6.1 times higher in needles than in twigs collected from the same trees. Average (±SE) residues in foliage samples collected from trees treated in 2019 ranged from 0.663 ± 0.243 to 0.564 ± 0.119 mg kg-1 , compared with 0.213 ± 0.033 and 0.225 ± 0.132 mg kg-1 in foliage from trees treated in 2018. Foliage residues from UPLC-MS/MS were consistently lower but strongly related to those from ELISA. Matrix effects appeared to disrupt ELISA analysis of twigs. None of the 25 trees treated in 2019 had live HWA when samples were collected in 2021 while low densities of HWA were observed on 52% of trees treated in 2018.

CONCLUSIONS

Dinotefuran was recovered from hemlock foliage, and to a lesser extent twigs, >2 years post-treatment. This, along with its relatively rapid translocation, suggests dinotefuran is a viable option for protecting declining or heavily infested hemlocks from HWA. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Climate Change and Local Host Availability Drive the Northern Range Boundary in the Rapid Expansion of a Specialist Insect Herbivore, Papilio cresphontes

Species distributions, abundance, and interactions have always been influenced by human activity and are currently experiencing rapid change. Biodiversity benchmark surveys traditionally require intense human labor inputs to find, identify, and record organisms limiting the rate and impact of scientific enquiry and discovery. Recent emergence and advancement of monitoring technologies have improved biodiversity data collection to a scale and scope previously unimaginable. Community science web platforms, smartphone applications, and technology assisted identification have expedited the speed and enhanced the volume of observational data all while providing open access to these data worldwide. How to integrate and leverage the data into valuable information on how species are changing in space and time requires new best practices in computational and analytical approaches. Here we integrate data from three community science repositories to explore how a specialist herbivore distribution changes in relation to host plant distributions and other environmental factors. We generate a series of temporally explicit species distribution models to generate range predictions for a specialist insect herbivore (Papilio cresphontes) and three predominant host-plant species. We find that this insect species has experienced rapid northern range expansion, likely due to a combination of the range of its larval host plants and climate changes in winter. This case study shows rapid data collection through large scale community science endeavors can be leveraged through thoughtful data integration and transparent analytic pipelines to inform how environmental change impacts where species are and their interactions for a more cost effective method of biodiversity benchmarking.

Competition with insectivorous ants as a contributor to low songbird diversity at low elevations in the eastern Himalaya

Competitive interactions between distantly related clades could cause complementary diversity patterns of these clades over large spatial scales. One such example might be ants and birds in the eastern Himalaya; ants are very common at low elevations but almost absent at mid-elevations where the abundance of other arthropods and insectivorous bird diversity peaks. Here, we ask if ants at low elevations could compete with birds for arthropod prey. Specifically, we studied the impact of the Asian weaver ant (Oecophylla smaragdina), a common aggressive ant at low elevations. Diet analysis using molecular methods demonstrate extensive diet overlap between weaver ants and songbirds at both low and mid-elevations. Trees without weaver ants have greater non-ant arthropod abundance and leaf damage. Experimental removal of weaver ants results in an increase in the abundance of non-ant arthropods. Notably, numbers of Coleoptera and Lepidoptera were most affected by removal experiments and were prominent components of both bird and weaver ant diets. Our results suggest that songbirds and weaver ants might potentially compete with each other for arthropod prey at low elevations, thereby contributing to lower insectivorous bird diversity at low elevations in eastern Himalaya. Competition with ants may shape vertebrate diversity patterns across broad biodiversity gradients.

Thermal niche predictors of alpine plant species

Within the context of species distribution models, scrutiny arises from the choice of meaningful environmental predictors. Thermal conditions are not the sole driver, but are the most widely acknowledged abiotic driver of plant life within alpine ecosystems. We linked long-term measurements of direct, plant-relevant, near-surface temperatures to plant species frequency. Across 47 sites located along environmental gradients within the Scandinavian mountain chain, the thermal preferences of 26 focal species of vascular plants, lichens, and bryophytes were explored. Based on partial least-squares regression, we applied a relative importance analysis to derive inductively the thermal variables that were best related to a species' frequency. To discover potential seasonal variability of thermal controls, analyses were both differentiated according to meteorological season and integrated across the entire year. The pronounced interspecies and temporal variability of thermal constraints revealed the thermal niches were much more nuanced and variable than they have commonly been represented. This finding challenges us to present, interrogate, and interpret data representing these thermal niches, which seems to be required in order to move beyond purely probabilistic and correlative descriptions of species' range limits. Thus, this information will help improve predictions of species distributions in complex arctic-alpine landscapes.

The Past, Present, and Future of the Hemlock Woolly Adelgid (Adelges tsugae) and Its Ecological Interactions with Eastern Hemlock (Tsuga canadensis) Forests

The nonnative hemlock woolly adelgid is steadily killing eastern hemlock trees in many parts of eastern North America. We summarize impacts of the adelgid on these forest foundation species; review previous models and analyses of adelgid spread dynamics; and examine how previous forecasts of adelgid spread and ecosystem dynamics compare with current conditions. The adelgid has reset successional sequences, homogenized biological diversity at landscape scales, altered hydrological dynamics, and changed forest stands from carbon sinks into carbon sources. A new model better predicts spread of the adelgid in the south and west of the range of hemlock, but still under-predicts its spread in the north and east. Whether these underpredictions result from inadequately modeling accelerating climate change or accounting for people inadvertently moving the adelgid into new locales needs further study. Ecosystem models of adelgid-driven hemlock dynamics have consistently forecast that forest carbon stocks will be little affected by the shift from hemlock to early-successional mixed hardwood stands, but these forecasts have assumed that the intermediate stages will remain carbon sinks. New forecasting models of adelgid-driven hemlock decline should account for observed abrupt changes in carbon flux and ongoing and accelerating human-driven land-use and climatic changes.