About

Rebecca Irwin is a Professor at North Carolina State University and serves as the Director of the Southeast Climate Adaptation Science Center within the Department of Applied Ecology. Her research focuses on the ecology and evolution of multiple-species interactions, pollination biology, and species invasions. Her lab investigates the complex web of interactions among biological communities, emphasizing the relative importance of direct and indirect effects of antagonists on plant-pollinator mutualisms. She explores how plant interactions with mutualists and antagonists simultaneously influence and constrain the evolution of nectar traits. Her work includes studying the impacts of environmental changes, such as seasonal snow cover, on solitary bee populations, and examining mechanisms and consequences of plant-pollinator-pathogen interactions. Dr. Irwin's research contributes to understanding the ecological and evolutionary dynamics of pollination systems and the effects of environmental stressors on pollinator health and plant reproduction.

Research topics

• Biology
• Ecology
• Botany
• Geography
• Horticulture
• Computer Science
• Environmental science
• Political Science
• Sociology
• Genetics
• Agroforestry
• Physical geography
• Geology
• Environmental resource management
• Agronomy
• Meteorology
• Atmospheric sciences
• Environmental planning

Selected publications

• Mechanisms and Consequences of Plant–Pollinator–Pathogen Interactions

  Annual Review of Ecology Evolution and Systematics · 2025-06-16 · 1 citations

  articleOpen access

  Infectious disease is a major driver of biodiversity loss, but how disease threatens pollinator communities remains poorly understood. Here, we review the plant–pollinator–pathogen literature to identify mechanisms by which plant and pollinator traits and community composition influence pathogen transmission and assess consequences of transmission on plant and pollinator fitness. We find that plant and pollinator traits that increase floral contact can amplify transmission, but community-level factors such as plant and pollinator abundance are often correlated and can counteract one another. Although disease reduces pollinator fitness in some species, little research has assessed cascading effects on pollination, and taxonomic representation outside of honey bees and bumble bees remains poor. Major open challenges include ( a ) disentangling correlations between plant and pollinator abundance to understand how community composition impacts pathogen transmission and ( b ) distinguishing when pathogen transmission results in disease. Addressing these issues, as well as expanding taxonomic representation of pollinators, will deepen our understanding of how pathogens impact diverse pollinator communities.

  PublisherDOI

• Elevated extinction risk in over one-fifth of native North American pollinators

  Proceedings of the National Academy of Sciences · 2025-03-24 · 22 citations

  articleOpen access

  Pollinators are critical for food production and ecosystem function. Although native pollinators are thought to be declining, the evidence is limited. This first, taxonomically diverse assessment for mainland North America north of Mexico reveals that 22.6% (20.6 to 29.6%) of the 1,579 species in the best-studied vertebrate and insect pollinator groups have elevated risk of extinction. All three pollinating bat species are at risk and bees are the insect group most at risk (best estimate, 34.7% of 472 species assessed, range 30.3 to 43.0%). Substantial numbers of butterflies (19.5% of 632 species, range 19.1 to 21.0%) and moths (16.1% of 142 species, range 15.5 to 19.0%) are also at risk, with flower flies (14.7% of 295 species, range 11.5 to 32.9%), beetles (12.5% of 18 species, range 11.1 to 22.2%), and hummingbirds (0% of 17 species) more secure. At-risk pollinators are concentrated where diversity is highest, in the southwestern United States. Threats to pollinators vary geographically: climate change in the West and North, agriculture in the Great Plains, and pollution, agriculture, and urban development in the East. Woodland, shrubland/chaparral, and grassland habitats support the greatest numbers of at-risk pollinators. Strategies for improving pollinator habitat are increasingly available, and this study identifies species, habitats, and threats most in need of conservation actions at state, provincial, territorial, national, and continental levels.

  PublisherOA PDFDOI

• Author response for "Extending sampling approaches for great crested newt (Triturus cristatus) eDNA monitoring"

  2025-10-14

  peer-review
  PublisherDOI

• Nectar Yeast Scent Additions Fail to Impact Overall Bouquet Composition and Bumble Bee Visitation in a Montane Herb

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Nectar yeast scent additions fail to impact overall bouquet composition and bumble bee visitation in a montane herb

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-10-17

  preprintOpen accessSenior author

  Abstract Premise of research The factors that mediate how foragers locate food supplies are of vital importance in understanding their energy acquisition and survival. Microbes that inhabit floral nectar can play outsized roles in altering nectar chemistry and nutrition, thereby affecting floral visitors. Methodology Here, we consider one such nectar microbe, the cosmopolitan, specialist nectar yeast, Metschnikowia reukaufii (Metschnikowiaceae), by inoculating a nectar analog of the subalpine wildflower, Corydalis caseana ssp. brandegeei (Fumariaceae), and then characterizing the yeast’s impacts on floral scent composition and the foraging behavior of its main pollinator, Bombus appositus (Apidae). We assessed foraging behavior of B. appositus in a flower array near the Rocky Mountain Biological Laboratory (Colorado, USA) to test the hypothesis that foragers preferentially visit yeast-inoculated flowers over sterile controls. Additionally, we assessed whether bees spent more time at, and fed more quickly on, yeast-inoculated flowers. In a separate experiment, we tested whether Corydalis inflorescences inoculated with M. reukaufii had different scent bouquets than sterile inflorescences. Pivotal results We found that bumble bee pollinators showed no preference for the focal yeast species, with inoculated nectar having no effect on number of flowers visited, time spent on individual flowers, or time spent accessing nectar. Further, the overall scent bouquet compositions of yeast-inoculated Corydalis inflorescences were not statistically significantly different than those of sterile inflorescences, despite increased emissions of several volatiles that are known to be produced by M. reukaufii . Conclusions Our findings suggest that B. appositus does not respond to the presence of M. reukaufii in the nectar of Corydalis, and instead, yeast-associated volatile emissions may serve as a reliable cue of a nectar reward that is unused by these pollinators. These findings suggest a few avenues for future research, particularly how morphologically complex, highly scented flowers interact with VOCs produced by nectar-inhabiting microbes, and how floral visitors interpret these signals.

  PublisherOA PDFDOI

• Standardized protocol for collecting community-level bee data

  Journal of Melittology · 2025-02-18 · 1 citations

  articleOpen access

  A key component of assessing bee biodiversity patterns and supporting bee conservation is documenting bee communities. When integrated with additional ecological data, community-level data help reveal the relative impact of local- and landscape-scale factors on bee taxa. As such, these data can inform management decisions to support bee diversity and mitigate environmental drivers of decline. However, methods for sampling bee communities vary greatly across projects, making it difficult to compare existing datasets or design new, interoperable studies. Here, we provide a standardized protocol for collecting community-level bee biodiversity data and offer guidance on inventorying, surveying, and monitoring of bee communities. We also present case studies to illustrate how different components of the protocol could be implemented. Although we discuss the benefits of collecting physical specimens, we emphasize the importance of responsible collecting and highlight key strategies to minimize environmental impact while maximizing the value of the work in new projects. This protocol is part of a series developed in association with the U.S. National Native Bee Monitoring Network to standardize bee monitoring practices.

  PublisherOA PDFDOI

• Standardized protocols for collecting data on bee-flower interactions and the associated floral community

  Journal of Melittology · 2025-09-26 · 1 citations

  articleOpen access

  Pollen and nectar from flowers constitute the primary food resources of bees, inextricably linking bee and flowering plant communities in space and time. Thus, our understanding of bee biology and distribution can be greatly enhanced by documenting interactions between bees and their host plant species. Plant-pollinator interaction data are routinely collected in studies with diverse research goals, but the lack of standardization in data collection has limited our ability to integrate datasets and address outstanding questions in bee ecology, conservation, and pollination biology. Here, we provide standardized protocols for (A) documenting plant-pollinator interactions and (B) quantifying associated floral resources available to foraging bees. These protocols can be combined for a more detailed understanding of plant-pollinator interactions and can be applied in inventories, surveys, and monitoring programs of bees. We also provide case studies demonstrating their application. We discuss tradeoffs that are inevitable in any methodological approach, including the use of lethal versus non-lethal sampling approaches, and highlight the need to prioritize rigorous testing of the scalability and generalizability of current methodologies. These protocols are part of a series developed in association with the U.S. National Native Bee Monitoring Network to standardize bee monitoring practices.

  PublisherOA PDFDOI

• Self-medicating behavior in bumble bees has cascading consequences for pollination and plant reproduction

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-07-24

  preprintOpen access

  ABSTRACT The sublethal effects of parasites can profoundly influence host traits and propagate to other trophic levels via indirect effects. To date, research on such trait-mediated indirect effects of parasites has focused on non-adaptive changes to host behavior, but adaptive sickness behaviors, such as self-medication, could also indirectly affect community composition and even the evolution of ‘medicinal’ traits in lower trophic levels. Here, we used interactions among the parasite Crithidia bombi , the bumble bee host Bombus impatiens , and Monarda fistulosa , a bee-pollinated plant with multiple chemotypes (genetically determined chemical phenotypes), to experimentally test whether parasite infection influences pollinator foraging, pollination success, and female plant reproduction differentially for medicinal vs. non-medicinal chemotypes. Compounds from three Monarda chemotypes reduced Crithidia infection intensity in bees (thymol, carvacrol, and 1,8-cineole; hereafter medicinal chemotypes), while two others did not (( R )-(–)-linalool and geraniol; hereafter non-medicinal chemotypes), compared to control sucrose solutions. We found evidence for self-medication in tent foraging choice assays: infected bees preferred medicinal chemotypes while uninfected bees foraged indiscriminately, leading to differences in pollen receipt. Crithidia infection had weak but compounding chemotype-specific effects on seed production, germination rate, and offspring chemotype, such that pollination by infected bees resulted in a 57% increase in the proportion of medicinal plants in the F1 generation compared to pollination by uninfected bees. Self-medicating behavior can have differential effects on the reproduction of medicinal vs. non-medicinal plants, suggesting that pollinator parasites may act as agents of selection on the phytochemistry of floral rewards. SIGNIFICANCE STATEMENT Parasite infection can alter host behavior in multiple ways, including by inducing self-medication. Self-medication has been documented in diverse animal taxa, yet we know very little about the broader ecological or evolutionary consequences of this response to infection. Here, we demonstrate that bumble bees infected with a common parasite show a preference for plant genotypes whose nectar contains antiparasitic compounds, and that this results in differential pollination and reproductive success for medicinal vs. non-medicinal individuals of a chemically polymorphic plant species. Our findings highlight self-medication as a previously understudied mechanism by which parasite infection could initiate cascading effects across trophic levels, and suggest that parasites may indirectly influence the evolution of plant traits via pollinator self-medication behaviors.

  PublisherDOI

• Extending sampling approaches for great crested newt ( <i>Triturus cristatus</i> ) <scp>eDNA</scp> monitoring

  Ecological Solutions and Evidence · 2025-10-01

  articleOpen access

  Abstract Environmental DNA (eDNA) monitoring has been used for great crested newt ( Triturus cristatus ) survey in the UK since the publication of a Defra‐funded trial in 2014. If eDNA results are to be used in support of a great crested newt licence, surveys must be performed during a 76‐day survey window (15 April–30 June) to coincide with peak great crested newt activity, and must follow the approved ethanol precipitation protocol. However, eDNA detection is possible in other months and filtration may be a more effective method of eDNA capture. We investigated whether the great crested newt eDNA survey season could be extended and filtration could be used for great crested newt eDNA capture by reviewing the available evidence and conducting a field study from April to October 2022. Paired water samples for ethanol precipitation and filtration were collected from 25 ponds once a month, resulting in 124 samples of each type. All samples ( N = 248) were analysed with the approved great crested newt quantitative PCR assay. Our results indicate that great crested newts can be reliably detected using both eDNA capture methods from April to August, with detection rates decreasing in September and October. Great crested newt eDNA detection was comparable or higher with filtration than ethanol precipitation. Practical implication. Acceptance of filtration for great crested newt eDNA surveys could allow more water to be processed for robust and reliable estimates of great crested newt presence. Extending the great crested newt eDNA survey season to August could allow more waterbodies to be surveyed for great crested newt presence (but not absence), and identification of sites that provide important habitat for great crested newts outside of the breeding season. This would also remove logistical challenges and costs associated with completing sampling within 11 weeks and laboratory analysis within 10 working days from sample receipt. Furthermore, great crested newt eDNA surveys could be more frequently carried out alongside monitoring for other species, which are typically surveyed from April to September/October or year‐round with conventional methods or eDNA surveys using filtration. This could enable infrastructure projects to develop more effective mitigation measures as well as reduce time required from surveyors and survey costs.

  PublisherOA PDFDOI

• Yeast Volatiles Promote Larceny in Bumble Bee Behavior

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

Recent grants

• DISSERTATION RESEARCH: Microbial mediation of polliator performance

  NSF · $9k · 2013–2014

• Consumer-Resource Interactions: Impacts of a plant invasion on the individual and colony performance of a native pollinator

  NSF · $528k · 2009–2013

• Pollination Webs: Impacts of a Plant Invasion on Native Plant-Pollinator Interactions, Linkage Strength, and Native Plant Reproduction

  NSF · $394k · 2004–2009

• Collaborative Research: The role of floral secondary compounds in bee performance and disease transmission in a natural ecosystem

  NSF · $198k · 2013–2016

• Collaborative Research: Context-Dependency in the Exploitation of Pollination Mutualisms

  NSF · $364k · 2014–2016

Frequent coauthors

• Lynn S. Adler

  University of Massachusetts Amherst

  93 shared

• David W. Inouye

  University of Maryland, College Park

  48 shared

• Alison K. Brody

  University of Vermont

  46 shared

• Judith L. Bronstein

  University of Arizona

  38 shared

• Evan C. Palmer‐Young

  29 shared

• Sarah K. Richman

  ETH Zurich

  27 shared

• Gabriella L. Pardee

  The University of Texas at Austin

  22 shared

• Elinor M. Lichtenberg

  University of North Texas

  22 shared

Labs

• Applied EcologyPI

  Not provided