Geology topics

Jeffrey G. Everett

Publications and source records attributed to Jeffrey G. Everett.

5 recordsLinked to original sources

USGS2026

Detecting bumble bees in the wild using environmental DNA: Development and validation of a qPCR assay for the endangered Franklin’s bumble bee (Bombus franklini)

Environmental DNA (eDNA) sampling is a noninvasive alternative to conventional methods of surveying insects that may be particularly useful for detecting pollinators. We developed a quantitative polymerase chain reaction (qPCR) assay to detect the DNA of Franklin’s bumble bee ( Bombus franklini ) from flower samples and conducted an initial test of the assay using samples collected within and around the historical range of the species. We further analyzed all samples using metabarcoding. Our qPCR assay successfully amplified B. franklini DNA and exhibited no cross-reactivity with nontarget bumble bee DNA during in silico and in vitro testing. We did not detect B. franklini DNA from field-collected flower samples using either qPCR or metabarcoding. However, metabarcoding analysis revealed DNA of at least 16 other bumble bee species. This finding underscores the potential utility of eDNA sampling for surveying bumble bees. Nondetection of B. franklini from field-collected flower samples may be due to the extreme rarity of the species; B. franklini is endangered and has not been observed in the wild since 2006. Our B. franklini assay is among the first bee-specific qPCR assays ever developed and provides proof of concept for additional assays that may improve detection rates of rare and endangered bees.

California, Oregon↗

USGS2025

Answering key bumble bee conservation questions by studying discovered wild nests: A Bombus affinis case study

The nesting ecology of wild bumble bees is not well resolved, but information learned from discovered nests can be of great conservation value. Data collected at nests on foraging patterns, caste-specific behaviour and health (e.g., pathogens) are invaluable for understanding bumble bee behaviour and ecology, but difficult to decipher solely from foraging observations away from the nest. Post-senescence nest excavation allows the estimation of colony size, caste numbers, documents pest incidence and provides opportunities to examine nest material for stressors (e.g., pesticides) and to use nest material for training purposes (e.g., conservation dogs). Wild nests are often found opportunistically, and there is an absence of standardised guidance on data collection. We provide an action plan to ensure the data collection is comparable across studies. This framework includes key conservation questions and methodological guidelines for both for in situ and post-season nest data collection and is ordered by increasing complexity of data collection methods. To illustrate our framework, we provide an example with recently discovered Bombus affinis (rusty patched bumble bee) nests. Through observations at B. affinis nests, we discovered novel patterns of activity, changing activity levels over time, the timing of male and gyne production, variable timing in nest senescence, and associations of nests with past rodent activity. Although individual nest discoveries may be of limited value in forwarding conservation strategies, the aggregate collections of many similar datasets can be of critical importance for species of conservation concern.

Insect Conservation and Diversity↗

USGS2024

Population genetics of museum specimens indicate decreasing genetic resiliency: The case of two bumble bees of conservation concern

Genetic resiliency is the likelihood that populations retain sufficient genetic diversity to respond to environmental change. It is rarely examined through time in conservation genetic studies due to challenges of acquiring and sequencing historical specimens. Focusing on populations of two sibling bumble bee species of conservation concern with different recent patterns of decline, we used museum specimens collected between 1960 and 2020 and 15 microsatellite markers to assess genetic resiliency (allelic richness, expected heterozygosity, and inbreeding) through time and across geographic space. We find evidence of decreasing allelic richness through time, starting at least 30 years before observed abundance declines in one species and at least 20 years before present in a species with apparently stable abundance. We also found increasing expected heterozygosity through time, indicating increased inbreeding, in the putatively stable species. We demonstrate that genetic measurements taken from specimens collected through time can be used to detect population decline in imperiled species before decreases in abundance are detected. We also demonstrate the importance of interpreting population genetic metrics within the context of historical patterns to assess species' conservation statuses. Finally, we discuss the limitations of currently available population genetic methods, including the influence of isolation by distance and sampling density on measurements of genetic structure, and the influence of demographic characteristics and choice of genetic markers on estimates of genetic diversity and structure. We call for further development of individual-based modeling methods to measure genetic structure, as opposed to commonly applied population-based metrics, to overcome these limitations.

Biological Conservation↗

USGS2024

Western and McKay's bumble bees occupancy trends and future projections

The Western and McKay's bumble bees, originally petitioned for listing as subspecies of the Western bumble bee (Bombus occidentalis) were previously among the most common western bumble bee species but have declined since the late 1990s (Graves et al. 2021). This report details an occupancy analysis utilizing pre-existing and newly collected bumble bee survey data to evaluate potential mechanisms associated with species trends across their distributions in western North America. In addition to evaluating spatially explicit changes in occupancy trends, we also sought to assess how widespread environmental conditions and stressors influence occupancy. Although changing climate, land cover, pesticides, and pathogens have all been identified as potential mechanisms for declines (Cameron et al. 2011, Kerr et al. 2015, Soroye et al. 2020), previous studies have not tied most climate hypotheses to bumble bee life histories or evaluated combined effects of more than 2 of these mechanisms at multi-state/ multiprovince scales. Using a scenario-based approach across climate models, emissions, and land cover scenarios, we projected future occupancy to mid-century (2050-2059). This analysis was conducted to support the Species Status Assessment (SSA) for Western and Mckay’s bumble bees being administered by the U.S. Fish & Wildlife Service (USFWS).

Report↗

USGS2023

Recent and future declines of a historically widespread pollinator linked to climate, land cover, and pesticides

The acute decline in global biodiversity includes not only the loss of rare species, but also the rapid collapse of common species across many different taxa. The loss of pollinating insects is of particular concern because of the ecological and economic values these species provide. The western bumble bee ( Bombus occidentalis ) was once common in western North America, but this species has become increasingly rare through much of its range. To understand potential mechanisms driving these declines, we used Bayesian occupancy models to investigate the effects of climate and land cover from 1998 to 2020, pesticide use from 2008 to 2014, and projected expected occupancy under three future scenarios. Using 14,457 surveys across 2.8 million km 2 in the western United States, we found strong negative relationships between increasing temperature and drought on occupancy and identified neonicotinoids as the pesticides of greatest negative influence across our study region. The mean predicted occupancy declined by 57% from 1998 to 2020, ranging from 15 to 83% declines across 16 ecoregions. Even under the most optimistic scenario, we found continued declines in nearly half of the ecoregions by the 2050s and mean declines of 93% under the most severe scenario across all ecoregions. This assessment underscores the tenuous future of B. occidentalis and demonstrates the scale of stressors likely contributing to rapid loss of related pollinator species throughout the globe. Scaled-up, international species-monitoring schemes and improved integration of data from formal surveys and community science will substantively improve the understanding of stressors and bumble bee population trends.

Proceedings of the National Academy of Sciences↗