About

Professor Rachael Winfree leads a research lab focused on investigating the causes and consequences of biodiversity change. The primary goal of her lab's research is to better understand the factors driving changes in biodiversity and the resulting ecological impacts. Her team works to advance the fundamental science of ecology while also contributing to evidence-based biodiversity conservation efforts. The lab members pursue diverse research questions within various global systems, unified by their use of pollinators and pollination as a model system to study ecological dynamics.

Research topics

• Biology
• Ecology
• Agroforestry
• Geography
• Agronomy
• Evolutionary biology

Selected publications

• Biodiversity–ecosystem function research must consider abundance and not just diversity

  Nature Reviews Biodiversity · 2025-04-11 · 6 citations

  article1st authorCorresponding
  PublisherDOI

• Floral Visitation and Pollen Collection by Native Bees in Temperate Deciduous Forests with Diverse Understory Communities

  Journal of Forestry · 2025-06-19 · 2 citations

  articleOpen accessSenior author

  Abstract The native bees associated with deciduous forest are likely the pre-colonial dominant bee fauna of the eastern United States, yet we lack the data on their resource use needed to guide management. We characterized bees’ floral resource use in mature deciduous forests managed by the National Park Service at sites spanning ~ 550 km of latitude in Indiana and Michigan. We collected floral visitation records for 4194 bee specimens representing 103 species, and data on bees’ pollen collection for 665 specimens. Our findings highlight differences among dominant bee genera in their floral resource use, especially pollen, and confirm the importance of canopy tree species and shrubs for bees in deciduous forests, even in those with diverse understory floral assemblages. As the largest, most spatially extensive source of data on bees’ use of floral resources within mature deciduous forests in North America, these records provide a useful reference point for forest bee conservation.

  PublisherOA PDFDOI

• Wild bees and landcover: bee species' body size does not predict the scale of effect, but bee phenology predicts association with landcover type

  Ecography · 2025-07-28 · 2 citations

  articleOpen accessSenior author

  Habitat is a key aspect of any species' niche and can affect populations at multiple spatial scales. Basic ecology and effective conservation thus require an understanding of which habitats matter and at what scales. Yet, habitat studies are rarely scale‐optimized, and what determines the scale(s) at which populations are affected by surrounding habitat (the ‘scale of effect') is poorly understood. In this study, we test the ‘mobility hypothesis,' which predicts that species with larger foraging ranges should have larger scales of effect. The mobility hypothesis is the most popular explanation of what determines species' scales of effect, but empirical support is mixed. We test the mobility hypothesis using wild bee species and, in doing so, also assess landscape‐scale habitat associations of 84 bee species. We collected 30 376 specimens of 84 bee species from 165 sites in the northeastern USA and used linear models to determine landcover associations and scales of effect for each species. To test the mobility hypothesis, we asked whether scales of effect varied with two mobility‐related traits – body size or sociality, which are the strongest known predictors of bee foraging ranges. Controlling the false discovery rate at 5%, we found 193 significant species–landcover associations across 60 (of 84) species. Scales of effect ranged from 100 to 8000 m (mode = 200 m; median = 1000 m) and, counter to the mobility hypothesis, were not associated with body size or sociality. As a result, we argue that ecologists should reconsider making assumptions about species' scales of effect and should instead explicitly measure scales of effect for their particular study organism and system. Considering the landcover associations themselves, we found these were broadly explained by phenology, with spring‐flying bees being associated with forests and summer‐flying bees being associated with more open, non‐forested habitats.

  PublisherOA PDFDOI

• Predicting interaction frequency in plant-pollinator networks

  2025-03-17 · 1 citations

  preprintOpen access

  Flowers and their pollinators represent a bipartite interaction system, whose links are hypothesised to be related to species traits. To explore whether we can predict the weight of this link, i.e. the frequency of interactions, in an validation network, we analysed 14 studies of pollinator-flower visitation network from around the world. We used information on species abundances, their traits and their phylogenetic (for plants) or taxonomic (for animals) position as predictors of interaction frequency, and fitted different statistical modelling approaches. We expected to see prediction quality on validation data to decay with spatial and temporal distance to the training networks. Similarly, we expect that changes in pollinator or plant composition will negatively affect predictive performance. Using the best-predicting modelling approach (randomForest), we indeed see a slight decay in predictive quality with plant and pollinator compositional distance. Temporal distance played little role, although predictions for one year ahead (or back) were better than across the season or across multiple years. The overall predictive power of our models was low (Spearman's $\rho \approx 0.4$), suggesting a very noisy system. Also, the most important predictor was abundance, as revealed by a parameter-free benchmark model that only used the cross-product of abundances to predict interaction frequency. Trait and phylogenetic information did not substantially improve predictive performance beyond abundance-based predictions. Across all studies, we failed to confirm a substantial contribution of ecological characteristics to pollinator-flower interaction frequency. One reason why predictions were relatively poor is that sampling effort is not standardised, and thus networks differed substantially in the observed number of interactions, network size, and interaction density. Also the pooling of networks across space or across time may have diluted preferences in the data, reducing their explanatory value. Finally, the majority of species in each network are rare, and the interaction information they provide may be much less relevant that that of common species. At present, we conclude that the frequencies of interactions are very difficult to predict, and using traits we cannot really do better than simply using abundance information.

  PublisherOA PDFDOI

• Differentiating nectar from pollen foraging affects estimates of specialization in plant-pollinator networks: a case study from the Bornean peat swamp forest canopy

  Journal of Tropical Ecology · 2025-01-01

  articleOpen accessSenior author

  Abstract Specialization is a core concept in the study of flowering plants and their relationships with floral visitors. In recent decades, researchers have increasingly used bipartite floral interaction networks to study these relationships. Networks are typically built from simple observations of floral visitation and ignore which resources visitors acquire during visits. However, flowers can provide nectar, pollen, or both, and floral visitor species may only forage for one or the other on a given plant. Here, using data we collected which differentiates nectar from pollen foraging for floral visitors to 15 Bornean rainforest tree species, we investigate whether estimates of specialization change when multiple floral resources are accounted for. We find that the same visitors have different estimated values of specialization when calculated using the overall visitation data (the standard approach), versus only nectar or pollen foraging. Differences in specialization estimates for flower-visiting taxa scale up to affect estimates of specialization for the whole community of floral visitors, with greater specialization found in nectar than pollen foraging. Our findings highlight some important considerations when using resource-agnostic visitation data in network-based studies of plant-pollinator relationships. In addition, this study represents one of the first network analyses of plant-pollinator interactions in a tropical rainforest canopy.

  PublisherDOI

• Wild insects and honey bees are equally important to crop yields in a global analysis

  Global Ecology and Biogeography · 2024-04-17 · 55 citations

  articleOpen accessSenior author

  Abstract Aim Most of the world's food crops are dependent on pollinators. However, there is a great deal of uncertainty in the strength of this relationship, especially regarding the relative contributions of the honey bee (often a managed species) and wild insects to crop yields on a global scale. Previous data syntheses have likewise reached differing conclusions on whether pollinator species diversity, or only the number of pollinator visits to flowers, is important to crop yield. This study quantifies the current state of these relationships and links to a dynamic version of our analyses that updates automatically as studies become available. Location Global. Time Period Present. Taxa studied Insect pollinators of global crops. Methods Using a newly created database of 93 crop pollination studies across six continents that roughly triples the number of studies previously available, we analysed the relationship between insect visit rates, pollinator diversity, and crop yields in a series of mixed‐effects models. Results We found that honey bees and wild insects contribute roughly equal amounts to crop yields worldwide, having similar average flower visitation rates and producing similar increases in yield per visit. We also found that pollinator species diversity was positively associated with increased crop yields even when total visits from all species are accounted for, though it was less explanatory than the total number of visits itself. Main conclusions Our analysis suggests a middle ground where honey bees are not responsible for the vast majority of crop pollination as has often been assumed in the agricultural literature, and likewise wild insects are not vastly more important than honey bees, as recent global analyses have reported. We also conclude that while pollinator diversity is less important than the number of pollinator visits, these typically involve many species, underscoring the importance of conserving a diversity of wild pollinators.

  PublisherOA PDFDOI

• Insufficient pollinator visitation often limits yield in crop systems worldwide

  Nature Ecology & Evolution · 2024-07-03 · 38 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

• Predicting plant–pollinator interactions: concepts, methods, and challenges

  Trends in Ecology & Evolution · 2024-01-22 · 21 citations

  article
  PublisherDOI

• Geometric effects of fragmentation are likely to mitigate diversity loss following habitat destruction in real‐world landscapes

  Global Ecology and Biogeography · 2024-03-13 · 4 citations

  articleOpen accessSenior author

  Abstract Aim Habitat conversion is the number one threat to biodiversity. The loss of biodiversity due to habitat loss might be exacerbated if species are harmed by fragmentation per se—the breaking apart of natural habitat that remains (hereafter fragmentation ). However, the evidence that species are harmed by habitat fragmentation is mixed. Studies at the patch scale tend to show that fragmentation reduces diversity due to negative demographic effects on species' dispersal, survival and fecundity. In contrast, studies at the landscape scale tend to show that fragmentation increases diversity. This discrepancy may be partly due to geometric effects, defined as greater species turnover between patches in more fragmented landscapes. Although these effects have been demonstrated theoretically and are expected to be stronger across larger spatial extents, it is unclear whether they are likely to occur in real‐world settings with both realistic landscape patterns and communities. Here, we investigated the possibility of geometric effects using simulations combined with real‐world landscape and community data. Location New Jersey, northeastern USA. Time period Current. Taxa studied Bees. Methods We focused on landscape sizes within the typical range for protected areas (36–576 ha), simulated forest loss using real landscape patterns, and simulated forest‐bee communities based on field data we collected. Results We found weak but positive effects of fragmentation: immediately following forest destruction, the most fragmented forests harboured up to 7.3% more species than the least fragmented forests of the same area, in agreement with observational studies of biodiversity along fragmentation gradients. In contrast to expectations, however, the overall effects of fragmentation did not change with spatial extent. Conclusions Our results suggest that fragmentation can mitigate biodiversity loss immediately following habitat destruction, but that the benefits do not vary strongly with spatial extent in real‐world landscapes and at extents relevant to land management.

  PublisherOA PDFDOI

• Individual bee foragers are less‐efficient transporters of pollen for plants from which they collect the most pollen in their scopae

  American Journal of Botany · 2023-05-11 · 15 citations

  articleOpen accessSenior author

  PREMISE: Bees provision most of the pollen removed from anthers to their larvae and transport only a small proportion to stigmas, which can negatively affect plant fitness. Though most bee species collect pollen from multiple plant species, we know little about how the efficiency of bees' pollen transport varies among host plant species or how it relates to other aspects of generalist bee foraging behavior that benefit plant fitness, such as specialization on individual foraging bouts. METHODS: We compared the pollen collected and transported by three bee species for 46 co-occurring plant species. Specifically, we compared the relative abundance of pollen taxa in the individual bees' scopae, structures where bees store pollen to provision larvae, with the relative abundance of pollen taxa on the rest of bees' bodies, which is more likely to be transferred to stigmas. RESULTS: Bees carried five times more pollen grains in their scopae than elsewhere on their bodies. Within foraging bouts, bees were relatively specialized in their pollen collection, but transported proportionally less pollen for the host plants on which they specialized. Across foraging bouts, two bee species transported proportionally less pollen for some of their host plants than for others, though differences didn't consistently follow the same trend as at the foraging bout scale. CONCLUSIONS: Our results suggest that foraging-bout specialization, which is known to reduce heterospecific pollen transfer, also results in less-efficient pollen transport. Thus, bee foragers that visit predominantly one plant species may have contrasting effects on that plant's fitness.

  PublisherOA PDFDOI

Recent grants

• SG: Broadening biodiversity-ecosystem functioning research to include mutualist networks

  NSF · $220k · 2020–2023

• Collaborative Research: The role of species dominance in mediating biodiversity-ecosystem function relationships across spatial scales

  NSF · $445k · 2016–2020

• Belmont Forum Collaborative Research: Open Library of Pollinator Biodiversity and Ecosystem Services Scenarios

  NSF · $179k · 2019–2023

Frequent coauthors

• Neal M. Williams

  University of California, Davis

  28 shared

• Claire Kremen

  University of British Columbia

  27 shared

• Ígnasi Bartomeus

  25 shared

• Daniel P. Cariveau

  University of Minnesota

  23 shared

• Jason Gibbs

  University of Manitoba

  20 shared

• Tina Harrison

  University of Louisiana at Lafayette

  14 shared

• Lucas A. Garibaldi

  National University of Río Negro

  14 shared

• Luísa G. Carvalheiro

  Universidade Federal de Goiás

  14 shared

Labs

• Winfree LabPI

Education

• Ph.D, Ecology & Evolutionary Biology

  Princeton University

  2001