- Author: Kathy Keatley Garvey
A five-member team led by postdoctoral researcher Daniel “Dani” Paredes of the Daniel Karp lab, UC Davis Department of Wildlife, Fish and Conservation Biology (WFCB), analyzed a 13-year government database to assess how the landscapes surrounding 400 Spanish vineyards influenced European grapevine moth (Lobesia botrana) outbreaks and insecticides application rates.
The article, "Landscape Simplification Increases Vineyard Pest Outbreaks and Insecticide Use," is now online.
“At harvest, we found pest outbreaks increased four-fold in simplified, vineyard-dominated landscapes compared to complex landscapes in which vineyards are surrounded by semi-natural habitats,” said lead author Paredes, who holds a doctorate in environmental sciences (2014) from the University of Granada, Spain. “Overall, our results suggest that simplified landscapes increase vineyard pest outbreaks and escalate insecticide spray frequencies. In contrast, vineyards surrounded by more productive habitats and more shrubland area are less likely to apply insecticides.”
Landscapes around farms are rarely managed to suppress damaging crop pests, partially because researchers rarely measure the key variables that drive farming decisions. This paper, however “shows how using really huge datasets—in this case generated by government employees working with farmers in Spain--can reveal how natural habitats surrounding agriculture can shape pest outbreaks and pesticide use in vineyards,” said co-author Jay Rosenheim, distinguished professor in the UC Davis Department of Entomology and Nematology.
A solution? At an individual level, farmers may better control L. botrana populations through planting native vegetation in and around their farm. Ideally, they would coordinate with each other to maintain and/or restore large patches of productive, shrubland habitats in the surrounding landscape.
Other co-authors are Rebecca Chaplin-Kramer, Natural Capital Project, Stanford University; and Silvia Winter, Institute of Plant Protection, University of Natural Resources and Life Sciences, Vienna, Austria.
Their work was financed by the research project SECBIVIT, or “scenarios for providing multiple ecosystem services and biodiversity in viticultural landscapes,” and a National Science Foundation/USA grant.
- Author: Kathy Keatley Garvey
In newly published research in Ecology Letters, "Dispersal Enchances Beta Diversity in Nectar Microbes," Vannette and colleague Tadashi Fukami of Stanford University's Department of Biology, examined microbial communities inhabiting the nectar of the sticky monkeyflower, Mimulus auranticus, at the Jasper Ridge Biological Preserve in California's Santa Cruz Mountains.
The flower, in the family Phrymacease, is a native shrub common in chaparral and coastal scrub habitats of California and Oregon. It is primarily pollinated by Anna's hummingbird. Other common pollinators include bumble bees, carpenter bees, and thrips.
Dispersal is considered a key driver of beta diversity, which is “the variation in species composition among local communities,” Vannette said.
They are the first to publish work showing that increased dispersal can increase biodiversity.
In their experiment, they reduced natural rates of dispersal by eliminating multiple modes of microbial dispersal. “Specifically we focused in nectar-inhabiting bacteria and yeasts that are dispersed among flowers by wind, insects and birds,” they said. “We imposed dispersal limitation on individual flowers and quantified microbial abundance, species composition and microbial effects on nectar chemistry.”
This work has direct implications for conservation of many organisms in addition to bacteria and yeast, suggesting that preserving routes of dispersal among habitat patches may be important in the maintenance of biodiversity. In contrast to previous work showing that dispersal can homogenize communities or make them more similar, the published work demonstrates that dispersal can in some cases generate communities that are more different from each other. The authors hypothesize that this could be driven by priority effects, where early arriving species change the species that can establish within that habitat.
Why focus on nectar-inhabiting microbes? Previous work by Vannette and others shows that microbial activity in nectar can alter nectar chemistry and influence plant-pollinator interactions by altering nectar chemistry. In the Ecology Letters study, microbes were also found to change nectar chemistry, explaining ~50% of the variation in sugar composition in the field. This suggests that nectar-inhabiting bacteria and yeast can influence the nectar rewards available to pollinators in a natural setting.
More broadly, “Studying the role of microbes in the environment addresses one of the biggest mysteries in science,” Vannette says. In her current work, she and her lab are investigating how microbial communities form, change, and function in their interactions with insects and plants. They are also researching how microorganisms affect plant defense against herbivores and plant attraction to pollinators.
Vannette, a former postdoctoral fellow at Stanford, joined the UC Davis Department of Entomology and Nematology faculty as an assistant professor in 2015.
Vannette's research was funded by the Gordon and Betty Moore Foundation through the Life Sciences Research Fellowship. Stanford also funded the research through grants from the National Science Foundation, the Terman Fellowship, and the Department of Biology at Stanford University.