Open Access Publications

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Open access publications by faculty, staff, postdocs, and graduate students in the Department of Entomology and Wildlife Ecology.

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Recycled Concrete Aggregate for Oyster Aquaculture
(Waste, 2024-06-27) Kang, Dong-Hee; Hunter, James G.; Chirnside, Anastasia
Recycled Concrete Aggregate (RCA) of the chemical and biological effects must be understood to avoid potential adverse impacts to the bay’s aquatic ecosystem. RCA application as a base material for oyster reefs did not adversely affect oyster spat growth and survival, or the surrounding environment. Evaluated RCA leaching for petroleum byproducts showed that RCA as a base material for oyster reefs did not leach any hydrocarbon chemicals, and no water extractable SVOC were detected. The research found potential RCA application to the Chesapeake Bay watershed as a bottom conditioning material for oyster aquaculture. Overall, the findings support the use of RCA for oyster aquaculture.
First Report of Chagas Disease Vector Species Triatoma sanguisuga (Hemiptera: Reduviidae) Infected with Trypanosoma cruzi in Delaware
(The American Journal of Tropical Medicine and Hygiene, 2024-03-26) Peterson, Jennifer K.; Hoyos, Juliana; Bartlett, Charles R.; Gottdenker, Nicole L.; Kunkel, Brian; Murphy, Carrie; Alvarado, Antonio
In July and October 2023, two live triatomine bugs were found inside a home in New Castle County, Delaware. The bugs were identified as Triatoma sanguisuga, the most widespread triatomine bug species in the United States. Triatoma sanguisuga is a competent vector of Trypanosoma cruzi, the causative agent of Chagas disease. The two specimens were tested via real-time PCR (qPCR) for infection with T. cruzi, and one of the specimens was positive. Despite T. sanguisuga being endemic to the area, attainment of accurate species identification and T. cruzi testing of the bugs required multiple calls to federal, state, private, and academic institutions over several months. This constitutes the first report of T. sanguisuga infected with T. cruzi in Delaware. In addition, this is the first published report of T. sanguisuga in New Castle County, the northernmost and most densely populated county in Delaware. New Castle County still conforms to the described geographic range of T. sanguisuga, which spans from Texas to the East Coast of the United States. The T. cruzi infection prevalence of the species has not been studied in the northeastern United States, but collections in southern states have found prevalences as high as 60%. The Delaware homeowner’s lengthy pursuit of accurate information about the vector highlights the need for more research on this important disease vector in Delaware.
Neonicotinoid exposure increases Varroa destructor (Mesostigmata: Varroidae) mite parasitism severity in honey bee colonies and is not mitigated by increased colony genetic diversity
(Journal of Insect Science, 2024-05-28) Bartlett, Lewis J.; Alparslan, Suleyman; Bruckner, Selina; Delaney, Deborah A.; Menz, John F.; Williams, Geoffrey R.; Delaplane, Keith S.
Agrochemical exposure is a major contributor to ecological declines worldwide, including the loss of crucial pollinator species. In addition to direct toxicity, field-relevant doses of pesticides can increase species’ vulnerabilities to other stressors, including parasites. Experimental field demonstrations of potential interactive effects of pesticides and additional stressors are rare, as are tests of mechanisms via which pollinators tolerate pesticides. Here, we controlled honey bee colony exposure to field-relevant concentrations of 2 neonicotinoid insecticides (clothianidin and thiamethoxam) in pollen and simultaneously manipulated intracolony genetic heterogeneity. We showed that exposure increased rates of Varroa destructor (Anderson and Trueman) parasitism and that while increased genetic heterogeneity overall improved survivability, it did not reduce the negative effect size of neonicotinoid exposure. This study is, to our knowledge, the first experimental field demonstration of how neonicotinoid exposure can increase V. destructor populations in honey bees and also demonstrates that colony genetic diversity cannot mitigate the effects of neonicotinoid pesticides.
Records of fleas (Siphonaptera) from Delaware
(Journal of Medical Entomology, 2024-05-17) Kennedy, Ashley C.; Winter, Wil S.; Gardner, Alfred L.; Woodman, Neal; Shifflett, Scarlet A.; Redus, Sierra; Newcomer, Jeffrey R.; Eckerlin, Ralph P.
We present an annotated checklist of fleas (Siphonaptera) known to occur in the state of Delaware based on an examination of Siphonaptera collections at the University of Delaware and the Carnegie Museum of Natural History, as well as new specimens of fleas we collected from wildlife, other hosts, and tick flags. We review published records and compile them herein with our new records, which include 3 species previously unreported from Delaware. With these additions, there are now 18 flea species from 19 avian and mammalian hosts documented from Delaware.
Genome divergence and reproductive incompatibility among populations of Ganaspis near brasiliensis
(Genes | Genomes | Genetics, 2024-05-08) Hopper, Keith R.; Wang, Xingeng; Kenis, Marc; Seehausen, M. Lukas; Abram, Paul K.; Daane, Kent M.; Buffington, Matthew L.; Hoelmer, Kim A.; Kingham, Brewster F.; Shevchenko, Olga; Bernberg, Erin
During the last decade, the spotted wing drosophila, Drosophila suzukii, has spread from eastern Asia to the Americas, Europe, and Africa. This fly attacks many species of cultivated and wild fruits with soft, thin skins, where its serrated ovipositor allows it to lay eggs in undamaged fruit. Parasitoids from the native range of D. suzukii may provide sustainable management of this polyphagous pest. Among these parasitoids, host-specificity testing has revealed a lineage of Ganaspis near brasiliensis, referred to in this paper as G1, that appears to be a cryptic species more host-specific to D. suzukii than other parasitoids. Differentiation among cryptic species is critical for introduction and subsequent evaluation of their impact on D. suzukii. Here, we present results on divergence in genomic sequences and architecture and reproductive isolation between lineages of Ganaspis near brasiliensis that appear to be cryptic species. We studied five populations, two from China, two from Japan, and one from Canada, identified as the G1 vs G3 lineages based on differences in cytochrome oxidase l sequences. We assembled and annotated the genomes of these populations and analyzed divergences in sequence and genome architecture between them. We also report results from crosses to test reproductive compatibility between the G3 lineage from China and the G1 lineage from Japan. The combined results on sequence divergence, differences in genome architectures, ortholog divergence, reproductive incompatibility, differences in host ranges and microhabitat preferences, and differences in morphology show that these lineages are different species. Thus, the decision to evaluate the lineages separately and only import and introduce the more host-specific lineage to North America and Europe was appropriate.
Evolving wildlife management cultures of governance through Indigenous Knowledges and perspectives
(The Journal of Wildlife Management, 2024-04-17) Fisk, Jonathan James; Leong, Kirsten Mya; Berl, Richard E. W.; Long, Jonathan W.; Landon, Adam C.; Adams, Melinda M.; Hankins, Don L.; Williams, Christopher K.; Lake, Frank K.; Salerno, Jonathan
Within governance agencies, academia, and communities alike, there are increasing calls to recognize the value and importance of culture within social-ecological systems and to better implement Indigenous sciences in research, policy, and management. Efforts thus far have raised questions about the best ethical practices to do so. Engaging with plural worldviews and perspectives on their own terms reflects cultural evolutionary processes driving paradigm shifts in 3 fundamental areas of natural resource management: conceptualizations of natural resources and ecosystems, processes of public participation and governance, and relationships with Indigenous Peoples and communities with differing worldviews. We broadly describe evolution toward these paradigm shifts in fish and wildlife management. We then use 3 case studies to illustrate the ongoing cultural evolution of relationships between wildlife management and Indigenous practices within specific historical and social-ecological contexts and reflect on common barriers to appropriately engaging with Indigenous paradigms and lifeways. Our case studies highlight 3 priorities that can assist the field of wildlife management in achieving the changes necessary to bridge incommensurable worldviews: acknowledging and reconciling historical legacies and their continued power dynamics as part of social-ecological systems, establishing governance arrangements that move beyond attempts to extract cultural information from communities to integrate Indigenous Knowledges into dominant management paradigms, and engaging in critical reflexivity and reciprocal, accountable relationship building. Implementing these changes will take time and a commitment to processes that may initially feel uncomfortable and unfamiliar but have potential to be transformative. Ethical and culturally appropriate methods to include plural and multivocal perspectives and worldviews on their own terms are needed to transform wildlife management to achieve more effective and just management outcomes for all.
Moths are less attracted to light traps than they used to be
(Journal of Insect Conservation, 2024-04-19) Battles, Ian; Burkness, Eric; Crossley, Michael S.; Edwards, Collin B.; Holmstrom, Kristian; Hutchison, William; Ingerson-Mahar, Joseph; Owens, David; Owens, Avalon C.S.
As evidence of global insect declines continues to mount, insect conservationists are becoming increasingly interested in modeling the demographic history of at-risk species from long-term survey data. However, certain entomological survey methods may be susceptible to temporal biases that will complicate these efforts. Entomological light traps, in particular, may catch fewer insects today than they once did due solely to increases in anthropogenic light pollution. Here we investigate this possibility by comparing the demographic histories of corn earworm moths (Helicoverpa zea) estimated from pairs of blacklight and pheromone traps monitored at the same farms. We find a stark decline in blacklight trap efficacy over 25 years of monitoring in Delaware, USA, mirrored over 10 years of monitoring in New Jersey, USA. While the precise causes of this decline remain a subject for discussion, the practical consequences are clear: insect conservationists cannot fully rely on long-term trends from entomological light traps.
Diversity and host specificity of Borrelia burgdorferi’s outer surface protein C (ospC) alleles in synanthropic mammals, with a notable ospC allele U absence from mixed infections
(Infection and Immunity, 2023-12-15) Shifflett, Scarlet A.; Ferreira, Francisco C.; González, Julia; Toledo, Alvaro; Fonseca, Dina M.; Ellis, Vincenzo A.
Interactions among pathogen genotypes that vary in host specificity may affect overall transmission dynamics in multi-host systems. Borrelia burgdorferi, a bacterium that causes Lyme disease, is typically transmitted among wildlife by Ixodes ticks. Despite the existence of many alleles of B. burgdorferi’s sensu stricto outer surface protein C (ospC) gene, most human infections are caused by a small number of ospC alleles [“human infectious alleles” (HIAs)], suggesting variation in host specificity associated with ospC. To characterize the wildlife host association of B. burgdorferi’s ospC alleles, we used metagenomics to sequence ospC alleles from 68 infected individuals belonging to eight mammalian species trapped at three sites in suburban New Brunswick, New Jersey (USA). We found that multiple allele (“mixed”) infections were common. HIAs were most common in mice (Peromyscus spp.) and only one HIA was detected at a site where mice were rarely captured. ospC allele U was exclusively found in chipmunks (Tamias striatus), and although a significant number of different alleles were observed in chipmunks, including HIAs, allele U never co-occurred with other alleles in mixed infections. Our results suggest that allele U may be excluding other alleles, thereby reducing the capacity of chipmunks to act as reservoirs for HIAs.
Biology and Management of Lesser Mealworm Alphitobius diaperinus (Coleoptera: Tenebrionidae) in Broiler Houses
(Journal of Integrated Pest Management, 2023-01-30) Sammarco, Ben C.; Hinkle, Nancy C.; Crossley, Michael S.
Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), the lesser mealworm, is a ubiquitous generalist  pest of poultry broiler and layer facilities, originating in southern Africa and now found worldwide. They spend their full life cycle within the litter and manure of poultry, causing structural damage to poultry houses, injuring birds, and acting as a reservoir for several avian pathogens, notably Salmonella spp. and Escherichia coli. Management commonly consists of spraying walls and floors of poultry houses with organophosphates, pyrethroids, neonicotinoids, or spinosyns between flocks, and periodic removal and replacement of litter. Populations have been observed to become resistant to specific insecticides after ca. 10 yr of consistent use and exhibit cross resistance to insecticides of the same mode of action. Alternative cultural and biological control methods have been identified but are not currently implemented. More research is needed regarding the economic impact of A. diaperinus, the mechanisms of its insecticide resistance, and patterns and mechanisms of colonization for effective integrated pest management programs to be devised and implemented.
Artificial light at night is a top predictor of bird migration stopover density
(Nature Communications, 2023-12-04) Horton, Kyle G.; Buler, Jeffrey J.; Anderson, Sharolyn J.; Burt, Carolyn S.; Collins, Amy C.; Dokter, Adriaan M.; Guo, Fengyi; Sheldon, Daniel; Tomaszewska, Monika Anna; Henebry, Geoffrey M.
As billions of nocturnal avian migrants traverse North America, twice a year they must contend with landscape changes driven by natural and anthropogenic forces, including the rapid growth of the artificial glow of the night sky. While airspaces facilitate migrant passage, terrestrial landscapes serve as essential areas to restore energy reserves and often act as refugia—making it critical to holistically identify stopover locations and understand drivers of use. Here, we leverage over 10 million remote sensing observations to develop seasonal contiguous United States layers of bird migrant stopover density. In over 70% of our models, we identify skyglow as a highly influential and consistently positive predictor of bird migration stopover density across the United States. This finding points to the potential of an expanding threat to avian migrants: peri-urban illuminated areas may act as ecological traps at macroscales that increase the mortality of birds during migration.
Seasonal patterns and protection status of stopover hotspots for migratory landbirds in the eastern United States
(Current Biology, 2024-01-22) Guo, Fengyi; Buler, Jeffrey J.; Smolinsky, Jaclyn A.; Wilcove, David S.
Summary Migratory landbirds in North America are experiencing dramatic population declines. Although considerable research and conservation attention have been directed toward these birds’ breeding and wintering grounds, far less is known about the areas used as stopover sites during migration. To address this knowledge gap, we used 5 years of weather surveillance radar data to map seasonal stopover densities of landbirds across the eastern United States during spring and autumn migration. We identified stopover hotspots covering 2.47 million ha that consistently support high densities of migratory landbirds in spring or autumn. However, only 16.7% of these sites are hotspots in both seasons. The distribution of hotspots is shifted eastward in autumn compared with spring. Deciduous forest is the most important habitat type in both seasons, with deciduous forest fragments embedded in broadly deforested regions having the highest probability of being hotspots. The concentration of birds in these forest fragments is stronger in spring, especially in the agricultural Midwest. We found generally higher stopover densities in protected areas than in unprotected areas in both seasons. Nonetheless, only one-third of identified stopover hotspots have some sort of protected status, and more than half of these protected hotspots are subject to extractive uses. A well-distributed network of well-protected stopover areas, complementing conservation efforts on the breeding and wintering grounds, is essential to sustaining healthy populations of migratory landbirds in North America.
New extralimital breeding records of saltmarsh sparrows (Ammospiza caudacuta) and Nelson's sparrows (Ammospiza nelsoni) and their implications
(Ecology and Evolution, 2023-09-19) Ruskin, Katharine J.; Clark, Jonathan D.; Hotopp, Alice; Kovach, Adrienne I.; Guido, Nicole A.; Hernandez, Dean L.; Peña, Colin; Webb, Samantha N.; Shriver, W. Gregory
Saltmarsh (Ammospiza caudacuta) and Nelson's (A. nelsoni) sparrows are sister taxa that breed in tidal marshes along the coast of the Northeastern United States and Canada. The Saltmarsh Sparrow breeds from mid-coast Maine south to Virginia, while the Acadian Nelson's Sparrow breeds from the Canadian maritime provinces south to northern Massachusetts. Here, we present three extralimital observations of breeding Saltmarsh (n = 2) and Nelson's (n = 1) sparrows. In 2021 and 2022, we observed Saltmarsh Sparrow females attending nests at Mendall Marsh, ME, and Milbridge, ME, respectively, approximately 60 and 110 km beyond the documented northern extent of the Saltmarsh Sparrow breeding range. In 2022, we observed a breeding-condition male Nelson's sparrow singing in the upriver portion of a marsh on Cape Cod, Massachusetts, approximately 115 km beyond the previously documented southern extent of the Nelson's Sparrow breeding range. We confirmed morphological species identification using a panel of microsatellite DNA loci. Due to both the well-documented population declines of these species in the region and the intensity of sampling effort undertaken in recent years, we suggest that these observations likely are not indicative of range expansion. However, they do indicate that these 2 taxa have the capacity to use and successfully reproduce in marshes well beyond their established breeding limits. Our findings provide novel insight into the potential for these taxa to occur and successfully breed outside their documented breeding ranges. Given increased interest in their conservation, these results support the idea that management actions aimed at creating or maintaining nesting habitat across both species ranges could benefit both taxa.
A Review of the Planthoppers (Hemiptera: Fulgoroidea) of the United States: Supplement 1
(Transactions of the American Entomological Society, 2023-04-28) Bartlett, Charles R.; Wilson, Stephen W.
Here we review changes to the planthopper (Hemiptera: Fulgoroidea) fauna north of Mexico since the publication of “A review of the planthoppers (Hemiptera: Fulgoroidea) of the United States” (Bartlett et al. 2014). There are 12 species in 4 families added to the fauna and 50 changes in the generic assignment in 4 families. The most significant faunal addition is the spotted lanternfly (Lycorma delicatula (White)), with populations reported in 14 states and vagrants in 3 more. We review some nomenclatural and taxonomic issues and provide a list of anomalous records that may represent unreported or undescribed species that require further investigation. All told, these additions and changes (excluding anomalous records) give totals of 175 genera and 924 species in 13 families of planthoppers, a net addition of 1 family, 8 genera, and 10 species to the tally provided in 2014.
A high-quality de novo genome assembly for clapper rail (Rallus crepitans)
(G3 Genes|Genomes|Genetics, 2023-05-02) Elizondo, Elisa C.; Faircloth, Brant C.; Brumfield, Robb T.; Shakya, Subir B.; Ellis, Vincenzo A.; Schmidt, Carl J.; Kovach, Adrienne I.; Shriver, W. Gregory
The clapper rail (Rallus crepitans), of the family Rallidae, is a secretive marsh bird species that is adapted for high salinity habitats. They are very similar in appearance to the closely related king rail (R. elegans), but while king rails are limited primarily to freshwater marshes, clapper rails are highly adapted to tolerate salt marshes. Both species can be found in brackish marshes where they freely hybridize, but the distribution of their respective habitats precludes the formation of a continuous hybrid zone and secondary contact can occur repeatedly. This system, thus, provides unique opportunities to investigate the underlying mechanisms driving their differential salinity tolerance as well as the maintenance of the species boundary between the 2 species. To facilitate these studies, we assembled a de novo reference genome assembly for a female clapper rail. Chicago and HiC libraries were prepared as input for the Dovetail HiRise pipeline to scaffold the genome. The pipeline, however, did not recover the Z chromosome so a custom script was used to assemble the Z chromosome. We generated a near chromosome level assembly with a total length of 994.8 Mb comprising 13,226 scaffolds. The assembly had a scaffold N50 was 82.7 Mb, L50 of four, and had a BUSCO completeness score of 92%. This assembly is among the most contiguous genomes among the species in the family Rallidae. It will serve as an important tool in future studies on avian salinity tolerance, interspecific hybridization, and speciation.
Relating weather radar data to migrating waterfowl abundance in the Rainwater Basin of Nebraska
(The Journal of Wildlife Management, 2023-06-01) Liu, Boyan; Kemink, Kaylan; Sieges, Mason; Smolinsky, Jaclyn; Varner, Dana; Buler, Jeffrey
Waterfowl migrations are large-scale events that involve millions of birds moving over broad geographic extents, which make them difficult to quantify and study. Historically, wildlife managers have relied mostly on field surveys, such as visual counts from the ground or air that sample at small spatial or temporal extents, or both. Combining field surveys with remote sensing data comprehensively collected over large spatial extents at high temporal frequency may improve the study of migrating waterfowl distributions. We tested the strength of the relationship between broad-scale weather surveillance radar data and fine-scale field surveys of waterfowl abundance at wetlands within the Rainwater Basin of Nebraska, USA, from 2017–2019. Radar reflectivity of waterfowl at the peak exodus of evening flights was positively correlated with diurnal waterfowl count data, although there was unexplained variation in the relationship. The association was also very similar across various time scales ranging from daily to monthly averages of waterfowl abundance. We suggest that human-based ground surveys can calibrate and leverage more comprehensive remote sensing data to get a broad understanding of waterfowl distributions during migration. Several confounding factors, such as spatial displacement between radar and survey observation, individual variation in orientation and body size, and identification of avian species sampled by radar, remain on the path to improving radar-based waterfowl estimates.
Autumn stopover hotspots and multiscale habitat associations of migratory landbirds in the eastern United States
(Proceedings of the National Academy of Sciences, 2023-01-09) Guo, Fengyi; Buler, Jeffrey J.; Smolinsky, Jaclyn A.; Wilcove, David S.
Significance: Understanding the en route habitat requirements of migratory birds is critical for conservation but difficult to know at a large scale. We mapped stopover density of landbirds during autumn migration for the eastern United States using radar data. At a coarse scale, we found that birds migrate across a relatively broad front, underscoring the importance of widespread, locally based conservation efforts. At finer scales, we identified stopover hotspots that consistently support high densities of migrants. We demonstrate that forests provide the most important habitats for autumn migrants and that deciduous forest fragments in heavily deforested regions support especially high densities of migrants. We also present evidence that the now-agriculture-dominated Midwest constitutes an inland migration barrier for forest birds. Abstract: Halting the global decline of migratory birds requires a better understanding of migration ecology. Stopover sites are a crucial yet understudied aspect of bird conservation, mostly due to challenges associated with understanding broad-scale patterns of transient habitat use. Here, we use a national network of weather radar stations to identify stopover hotspots and assess multiscale habitat associations of migratory landbirds across the eastern United States during autumn migration. We mapped seasonal bird densities over 5 y (2015 to 2019) from 60 radar stations covering 63.2 million hectares. At a coarse scale, we found that landbirds migrate across a broad front with small differences in migrant density between radar domains. However, relatively more birds concentrate along the Mississippi River and Appalachian Mountains. At a finer scale, we identified radar pixels that consistently harbored high densities of migrants for all 5 y, which we classify as stopover hotspots. Hotspot probability increased with percent cover of all forest types and decreased with percent cover of pasture and cultivated crops. Moreover, we found strong concentrating effects of deciduous forest patches within deforested regions. We also found that the prairie biome in the Midwest (now mostly cropland) is likely a migration barrier, with large concentrations of migrants at the prairie–forest boundary after crossing the agricultural Midwest. Overall, the broad-front migration pattern highlights the importance of locally based conservation efforts to protect stopover habitats. Such efforts should target forests, especially deciduous forests in highly altered landscapes. These findings demonstrate the value of multiscale habitat assessments for the conservation of migratory landbirds.
Impact of heat waves on egg survival and biological performance across life stages in the Asian corn borer
(Entomologia Experimentalis et Applicata, 2023-01-02) Quan, Yudong; Mason, Charles E.; He, Kanglai; Wang, Zhenying; Wei, Hongyi
One of the many extreme events as a result of climate change is the frequent appearance of extraordinarily daily high temperatures that can directly drive an insect's adaptive response. Insects have complex life cycles that may uncouple temperature's effects in one stage from the physiology in the next. In this study we focused on the Asian corn borer (ACB), Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae), one of the most important pests of maize (corn) in Asia, investigated the consequences of eggs exposed to ecologically relevant heat shock regimes, simulating heat waves at extreme high temperature. This consisted of five 90-min heat treatments separated by two degrees that ranged from 37 to 45°C for three consecutive days compared to a constant temperature of 25°C. Temperature that triggered mortality was between 39 and 41°C. Egg hatching significantly declined when temperature was 41°C or higher. There was no egg hatching at 45°C. Developmental times were significantly prolonged and the larval growth rate became slower in treatments of 41 and 43°C. There were no significant differences in pupal mass, fecundity, and sex ratio among treatments. Life table parameters showed significant adverse effects at treatments of 41 and 43°C. Depending on the fitness response of the ACB, environmental heat waves can be classified into three categories based on temperature criteria, i.e., adaptable (35–39°C), critical (39–45°C), and fatal (≥45°C). The findings of the present study will serve as an important reference for forecasting the population dynamics of the ACB.
First record of the family Issidae (Hemiptera, Auchenorrhyncha, Fulgoroidea) from the Hawaiian Islands
(Biodiversity Data Journal, 2022-03-22) Gnezdilov, Vladimir; Bartlett, Charles R.
Background: Euroxenus vayssieresi (Bonfils, Attie & Reynaud, 2001) (Issinae, Sarimini) was described (in the genus Borbonissus Bonfils, Attie & Reynaud, 2001) from Réunion Island, in the Indian Ocean and, previous to this report, has not been recorded elsewhere. Euroxenus vayssieresi is here illustrated and re-described to improved taxonomic diagnosis. New information: Euroxenus vayssieresi is recorded for the first time from the Island of Hawaii in the Hawaiian Archipelago. This is first record of the family Issidae from the Hawaiian Archipelago.
Past and recent farming degrades aquatic insect genetic diversity
(Molecular Ecology, 2022-06-30) Crossley, Michael S.; Latimer, Christopher E.; Kennedy, Christina M.; Snyder, William E.
Recent declines in once-common species are triggering concern that an environmental crisis point has been reached. Yet, the lack of long abundance time series data for most species can make it difficult to attribute these changes to anthropogenic causes, and to separate them from normal cycles. Genetic diversity, on the other hand, is sensitive to past and recent environmental changes, and reflects a measure of a populations' potential to adapt to future stressors. Here, we consider whether patterns of genetic diversity among aquatic insects can be linked to historical and recent patterns of land use change. We collated mitochondrial cytochrome c oxidase subunit I (COI) variation for >700 aquatic insect species across the United States, where patterns of agricultural expansion and intensification have been documented since the 1800s. We found that genetic diversity was lowest in regions where cropland was historically (pre-1950) most extensive, suggesting a legacy of past environmental harm. Genetic diversity further declined where cropland has since expanded, even after accounting for climate and sampling effects. Notably though, genetic diversity also appeared to rebound where cropland has diminished. Our study suggests that genetic diversity at the community level can be a powerful tool to infer potential population declines and rebounds over longer time spans than is typically possible with ecological data. For the aquatic insects that we considered, patterns of land use many decades ago appear to have left long-lasting damage to genetic diversity that could threaten evolutionary responses to rapid global change.
Opposing global change drivers counterbalance trends in breeding North American monarch butterflies
(Global Change Biology, 2022-06-10) Crossley, Michael S.; Meehan, Timothy D.; Moran, Matthew D.; Glassberg, Jeffrey; Snyder, William E.; Davis, Andrew K.
Many insects are in clear decline, with monarch butterflies (Danaus plexippus) drawing particular attention as a flagship species. It is well documented that, among migratory populations, numbers of overwintering monarchs have been falling across several decades, but trends among breeding monarchs are less clear. Here, we compile >135,000 monarch observations between 1993 and 2018 from the North American Butterfly Association's annual butterfly count to examine spatiotemporal patterns and potential drivers of adult monarch relative abundance trends across the entire breeding range in eastern and western North America. While the data revealed declines at some sites, particularly the US Northeast and parts of the Midwest, numbers in other areas, notably the US Southeast and Northwest, were unchanged or increasing, yielding a slightly positive overall trend across the species range. Negative impacts of agricultural glyphosate use appeared to be counterbalanced by positive effects of annual temperature, particularly in the US Midwest. Overall, our results suggest that population growth in summer is compensating for losses during the winter and that changing environmental variables have offsetting effects on mortality and/or reproduction. We suggest that density-dependent reproductive compensation when lower numbers arrive each spring is currently able to maintain relatively stable breeding monarch numbers. However, we caution against complacency since accelerating climate change may bring growing threats. In addition, increases of summer monarchs in some regions, especially in California and in the south, may reflect replacement of migratory with resident populations. Nonetheless, it is perhaps reassuring that ubiquitous downward trends in summer monarch abundance are not evident.

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