Biology subjects

Koch, J. B. U.

Publications and source records attributed to Koch, J. B. U..

5 recordsLinked to original sources

bioRxiv2026

Divergent Behavioral Responses to Resource Limitations by Honey Bees, Bumble Bees, and Mason Bees

Resource limitation is a central ecological phenomenon shaping pollinator behavior, reproduction, and community dynamics. Many studies have looked at these interactions, but few have forced competition and explored species-specific responses. Here, we experimentally evaluated behavioral and reproductive responses of honey bees (Apis mellifera), bumble bees (Bombus impatiens), and mason bees (Osmia bruneri) in controlled single and multispecies foraging environments. Across all treatments, each species exhibited distinct forms of behavioral compensation when exposed to increased interspecific competition. Apis mellifera reduced the number of foraging events in mixed species cages yet showed variation in colony growth. B. impatiens increased foraging effort when co-foraging with other species, but this heightened activity did not translate into increased colony growth. O. bruneri maintained consistent foraging effort across treatments but exhibited reduced reproduction and a marked shift in floral host use, switching from preferred species (Phacelia tanacetifolia and Melilotus alba) to less-preferred alternatives (Collinsia grandiflora and Trifolium incarnatum) when competing with social bees. Regardless of compensatory behaviors, all three species demonstrated reduced reproductive success under competitive conditions. Our findings underscore the importance of evaluating interspecific competition when placing managed bees in natural or semi-natural habitats to avoid inadvertently stressing wild or managed bee populations and taking into consideration species-specific responses in addition to community level responses to competition.

ecology↗

bioRxiv2026

Drought reduces solitary bee reproduction and skews sex ratios

The Intermountain West of the United States has experienced years of extreme drought and increased temperatures. Increasing temperature and droughts can negatively impact native species that are locally adapted to environmental conditions that have persisted prior to the Anthropocene. Bees, especially solitary bees, provide critical ecosystem services because they pollinate ~90% of all flowering plants. Here we asked how drought impacted the reproduction of Osmia bruneri, a solitary mason bee. We released 20 females in nesting blocks at 21 field sites across four years (2020 - 2023) in the Bear River Mountains of northern Utah. O. bruneri reproduction was positively correlated with winter precipitation, and sex ratio was skewed in years that had a yearlong drought from the expected female to male ratio of 1.3:1 to 0.33:1. These results suggest that O. bruneri is susceptible to winter precipitation droughts. Not only was there a decrease in the total number of cells provisioned but the overall number of females produced decreased significantly during season long drought conditions. Continuous droughts can lead to a local level population decline and could contribute to overall species declines. Identifying the effects of extreme drought on solitary bee fecundity is critical for supporting effective management practices and conservation prioritization. Additionally, the results suggest that preceding winter precipitation can act as an indicator for predicting nesting success in wild solitary bees and may be an overall indicator of habitat quality.

ecology↗

bioRxiv2026

Agricultural intensification favours an introduced bumble bee over its native congener through differences in foraging range, habitat association, and lineage continuity

Agricultural intensification can enhance the expansion of introduced species which are highly adapted to human-modified landscapes, but the mechanisms by which this occurs are often unclear. Here we investigate the spatial ecology of a rapidly expanding introduced bumble bee (Bombus impatiens) and a native congener (B. mixtus) in agricultural landscapes of southwestern British Columbia, Canada. We used microsatellite genotyping and spatially explicit capture-recapture models to compare the foraging distance of the two species, and fitted hierarchical models to compare their abundance, behaviour (nest searching vs foraging), and lineage survival as a function of landscape composition and configuration. We found that B. impatiens had a broader foraging range than B. mixtus. B. impatiens colony/worker abundance were positively associated with the surrounding area of residential gardens and field edges, but decreased relative to B. mixtus abundance in response to increasing seminatural area. In contrast, B. mixtus colony abundance decreased in landscapes with a greater area of intensively managed berry crops. We observed fewer B. impatiens queens per survey in landscapes with more low-disturbance landcover, and hypothesize space use of this species could be shaped by concentration on potential nesting habitat. Consistent with this observation, nest searching behaviour was more common for B. impatiens queens, while B. mixtus queens varied in their use of certain habitat types for nest searching and were primarily observed foraging, suggesting these two species derive different value from agricultural landscapes during colony establishment. Finally, we found that the rate of lineage re-capture between 2022 colonies and 2023 spring queens was nearly 10-fold higher for B. impatiens than for B. mixtus, indicating a greater capacity of the introduced species to complete its life cycle in agro-natural landscape mosaics. Our results suggest that differences in spatial ecology may contribute to the differential success of these two species in human-modified landscapes, and provide insight into the mechanisms by which land-use change shapes community composition. Graphical abstractColoured diagrams of B. mixtus and B. impatiens are credited to Elaine Evans and the Xerces Society, with permission. O_FIG O_LINKSMALLFIG WIDTH=184 HEIGHT=200 SRC="FIGDIR/small/723627v2_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@136085aorg.highwire.dtl.DTLVardef@5e7b7eorg.highwire.dtl.DTLVardef@fdaa1borg.highwire.dtl.DTLVardef@1aaf4f9_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗

bioRxiv2026

Pervasive and dynamic gut dysbiosis in wild bumble bees is linked to the host life cycle

Stressors can shift the microbiome into an altered, "dysbiotic" state that reduces host fitness. While well-studied in humans and laboratory models, the prevalence, predictability, and drivers of dysbiosis in wildlife remain unclear. We addressed these questions by monitoring gut microbiomes of wild bumble bees in Southern California, focusing on Bombus vosnesenskii, a major pollinator in western North America. More than a third of all B. vosnesenskii bees exhibited dysbiosis, when defined as a >50% replacement of host-specialized core bacteria by environmental bacteria. This replacement covaried with increased alpha and beta diversity, an enrichment of oxygen-tolerant taxa, and pathogen infection--all common hallmarks of dysbiosis in other hosts. Other co-occurring Bombus, including two at-risk species, also exhibited dysbiosis. In B. vosnesenskii, dysbiosis was not correlated with certain stressors, such as heat or resource limitation, although other, unmeasured stressors cannot be ruled out. We next examined how dysbiosis varied over two years of sampling. In the first year, dysbiosis emerged only late in the season, when bumble bee colonies normally reproduce and then senesce. Two years later, following an intervening year with historic rainfall and elevated resources, dysbiosis was entrenched throughout the season. These findings show that dysbiosis is both pervasive and highly dynamic in wild bumble bees. The dynamics coincide with host life cycle transitions and environmental change, but the underlying causality remains uncertain. Given that dysbiosis may harm host health, we argue that long-term microbiome monitoring should be considered both for bumble bees and for other wildlife of conservation concern.

microbiology↗

bioRxiv2024

Chromosome-scale genome assembly of the Hunt bumble bee, Bombus huntii Greene, 1860, a species of agricultural interest

The Hunt bumble bee, Bombus huntii, is a widely distributed pollinator in western North America. The species produces large colony sizes in captive rearing conditions, experiences low parasite and pathogen loads, and has been demonstrated to be an effective pollinator of tomatoes grown in controlled environment agriculture systems. These desirable traits have galvanized producer efforts to develop commercial B. huntii colonies for growers to deliver pollination services to crops. To better understand B. huntii biology and support population genetic studies and breeding decisions, we sequenced and assembled the B. huntii genome from a single haploid male. High-fidelity sequencing of the entire genome using PacBio, along with HiC sequencing, led to a comprehensive contig assembly of high continuity. This assembly was further organized into a chromosomal arrangement, successfully identifying 18 chromosomes spread across the 317.4 Mb assembly with a BUSCO score indicating >98% completeness. Synteny analysis demonstrates shared chromosome number (n = 18) with B. terrestris, a species belonging to a different subgenus, matching the expectation that presence of 18 haploid chromosomes is an ancestral trait at least between the subgenera Pyrobombus and Bombus sensu stricto. In conclusion, these assembly outcomes, alongside the minimal tissue sampled destructively, showcase techniques for producing efficient, comprehensive, and continuous genome arrangements.

genomics↗