- Author: Kathy Keatley Garvey
Lead author Clara Stuligross, a doctoral student in the lab of pollination ecologist Neal Williams, a professor in the Department of Entomology and Nematology, teamed with Williams to study the results of food scarcity and pesticide exposure.
They exposed the bees to the neonicotinoid insecticide imidacloprid, widely used in agriculture, and found that the combined threats—imidacloprid exposure and the loss of flowering plants—reduced the bee's reproduction by 57 percent, resulting in fewer female offspring.
Of the two stressors—food scarcity and pesticide exposure—pesticide exposure showed the great impact on nesting activity and the number of offspring produced, they said.
The study, Pesticide and Resource Stressors Additively Impair Wild Bee Reproduction, accomplished in the spring of 2018 on the grounds of the UC Davis Harry H. Laidlaw Jr. Facility, is published in the journal Proceedings of the Royal Society B.
Other scientists have conducted similar research on honey bees, but this is the first comparable research on wild bees in field or semi-field conditions.
The blue orchard bee, nicknamed BOB, is a dark metallic mason bee, smaller than a honey bee. It is prized for pollinating almond, apple, plum, pear, and peach trees. California almond growers often set up bee boxes or bee condos for them in their orchards to aid in the honey bee pollination. In the wild, the bees nest in reeds or natural holes.
To study the survival, nesting and reproduction of the blue orchard bee, they set up nesting females in large flight cages, some with high densities of wildflowers and others with low densities that were treated “with or without the common insecticide, imidacloprid.” Bees are commonly exposed to insecticides when they forage on treated flowers.
"Understanding how multiple stressors interplay is really important, especially for bee populations in agricultural systems, where wild bees are commonly exposed to pesticides and food can be scarce,” said Stuligross, who holds a bachelor of arts degree in environmental studies (2014) from Earlham College, Richmond, Ind. She joined the UC Davis ecology doctoral program in 2016.
Onset of Nesting Delayed
Key factors in affecting bee reproduction are the probability that females will nest and the total number of offspring they have. The UC Davis research found that pesticide-exposed and resource-deprived female bees delayed the onset of nesting by 3.6 days and spent five fewer days nesting than unexposed bees.
Professor Williams pointed out that this is a substantial delay because bees nest only for a few weeks, and it's crucial to reproduce female offspring to carry on the future generations. “Fewer females will reduce the reproductive potential of subsequent generations," said Williams, a UC Davis Chancellor's Fellow and a newly elected fellow of the California Academy of Sciences.
They found that only 62 percent of pesticide-exposed bees produced at least one daughter compared to 92 percent of bees not exposed to pesticides.
The study drew support from a UC Davis Jastro Research Award, a UC Davis Ecology Graduate Research Fellowship, a National Science Foundation Graduate Research Fellowship, and the UC Davis bee biology facility
The blue orchard bee bee is one of the few native pollinators that is managed in agriculture. North America has 140 species of Osmia, according to a Pollinator Partnership (PP) article in a U. S. Forest Service publication, authored by entomologist and PP member Beatriz Moisset and PP director Vicki Wojcik. “Mason bees use clay to make partitions and to seal the entrance,” they wrote. “This unique mud-building behavior leads to their common designation as mason bees. Honey bees are very important to commercial agriculture, but native bees like the blue orchard bees are better and more efficient pollinators of native crops.”
Imidacloprid, a systemic insecticide that acts as an insect neurotoxin, is used to control sucking insects, termites, some soil insects and fleas on pets, according to National Pesticide Information Center. It mimics nicotine, toxic to insects, which is naturally found in many plants, including tobacco. More than 400 products for sale in the United States contain imidacloprid.
- Author: Kathy Keatley Garvey
Newly published UC Davis research analyzing modern-day and museum collections of monarch butterflies over a 200-year period indicates that the loss of migration and range expansion leads to smaller and shorter wings.
The research, “Two Centuries of Monarch Butterfly Collections Reveal Contrasting Effects of Range Expansion and Migration Loss on Wing Traits,” appears this week in the Proceedings of the National Academy of Sciences.
“We measured the wings of 6,000 museum specimens of monarch butterflies collected from 1856 to the present, as well as contemporary wild-caught monarchs from around the world,” said lead author Micah Freedman, a former UC Davis doctoral candidate in population biology and now a postdoctoral fellow at the University of Chicago.
“The major implications of the research,” Freedman said, “are that it shows (1) loss of migration can affect the evolution of monarch butterflies over contemporary time scales--dozens to hundreds of years; and (2) monarchs with large forewings are better-suited for long distance movement, and this likely contributed to their global expansion over the past 200 years.”
Co-Authors of PNAS Paper
Freedman works closely with noted migratory animal authority and co-author Hugh Dingle, emeritus professor, UC Davis Department of Entomology and Nematology, who received a 2014 UC Davis Edward A. Dickson Professorship Award to research “Monarchs in the Pacific: Is Contemporary Evolution Occurring on Isolated Islands?” They co-authored the research with Sharon Strauss, professor and Santiago Ramirez, associate professor, Center for Population Biology and the Department of Evolution and Ecology.
Their research documents how migration-associated traits may be favored during range expansion but disfavored when species cease seasonal migration. “Furthermore, it highlights the value of museum collections by combining historical specimens with experimental rearing to demonstrate contemporary evolution of migration-associated traits in natural monarch populations,” Freedman said.
Said Dingle: “At a time when museum collections are under pressure from a scarcity of funding, the results also show just how valuable such collections can be to evolutionary research and to the understanding of ongoing biological processes in the face of anthropogenic change.”
In their abstract, they pointed out that “migratory animals exhibit traits that allow them to exploit seasonally variable habitats. In environments where migration is no longer beneficial, such as oceanic islands, migration-association traits may be selected against or be under relaxed selection.”
“Monarch butterflies are best known for their continent-scale migration in North America but have repeatedly become established as non-migrants in the tropical Americas and on Atlantic and Pacific Islands,” they wrote. “These replicated non-migratory populations provide natural laboratories for understanding the rate of evolution of migration-associated traits.”
What They Determined
They determined (1) how wing morphology varies across the monarch's global range, (2) whether initial long-distance founders were particularly suited for migration and (3) whether recently-established non-migrants show evidence for contemporary phenotypic evolution.
Under controlled conditions in a UC Davis lab, they also reared more than 1000 monarchs from six populations around the world and measured migration-associated traits.
“Historical specimens show that initial founders are (1) well-suited for long-distance movement and (2) loss of seasonal migration is associated with reductions in forewing size and elongation,” they related. “Monarch butterflies raised in a common garden from four derived non-migratory populations exhibit genetically based reductions in forewing size, consistent with a previous study.”
Dingle said the findings “provide a compelling example of how migration-associated traits may be favored during the early stages of range expansion, and also the rate of reductions in those same traits upon loss of migration.”
Statistics show that the population of monarch butterflies in the United States has declined by 90 percent over the past 20 years.
Undergoing Contemporary Evolution
The monarch butterflies established just 200 years ago in remote Pacific Islands are undergoing contemporary evolution through differences in their wing span and other changes, Dingle said. He and Freedman studied monarchs in the Pacific Islands for a week in 2016 in a project funded by Dingle's UC Davis emeritus faculty grant, the Edward A. Dickson Professorship Award. The research involved measuring the wingspans of Guam monarchs to determine whether there has been an evolutionary decrease in size or shape due to their migration-free lifestyle on the island. They also measured the wings of monarchs in the University of Guam's museum collection.
An analysis of a monarch population in Hawaii shows that resident monarchs have shorter, broader wings than the long-distance migrants, Dingle noted. The Hawaii butterfly wings were shorter than the eastern U.S. long-distance migrants, but “not so short-winged as the residents in the Caribbean or Costa Rica, which have been present in those locations for eons, rather than the 200 years for Hawaii.”
Dingle, author of two editions of Migration: The Biology of Life on the Move (Oxford University Press), a fellow of the American Association for the Advancement of Science and a past president of the Animal Behavior Society, said previous studies by various authors revealed that migrant and long-resident monarchs exhibit different wing shapes. "Thus, it was desirable to examine populations with only short residency to see if the same phenomenon was evident.”
Dingle, who served as a UC Davis entomology professor from 1982 to 2002, achieving emeritus status in 2003, has engaged in research throughout the world, including the UK, Kenya, Thailand, Panama, Germany and Australia. National Geographic featured Dingle in its cover story on “Great Migrations” in November 2010. LiveScience interviewed him for its November 2010 piece on“Why Do Animals Migrate?”
The Bohart Museum of Entomology at UC Davis was among the 22 global museum collections studied. The research also included private collections and online databases. Freedman and assistant Christopher Jason reared some of the butterflies included in the PNAS paper in a UC Davis greenhouse.
The project drew funding from the National Science Foundation (NSF) Graduate Research Fellowship Program, the NSF East Asia and Pacific Summer Institute Program, the UC Davis Center for Population Biology, and the National Geographic Society to Freedman, as well as the Dickson Emeritus Professor Award to Dingle, a California Agricultural Experiment Station grant to Strauss, and a David and Lucille Packard Fellowship to Ramirez.
The abstract:
“Migratory animals exhibit traits that allow them to exploit seasonally variable habitats. In environments where migration is no longer beneficial, such as oceanic islands, migration-association traits may be selected against or be under relaxed selection. Monarch butterflies are best known for their continent-scale migration in North America but have repeatedly become established as non-migrants in the tropical Americas and on Atlantic and Pacific Islands. These replicated non-migratory populations provide natural laboratories for understanding the rate of evolution of migration-associated traits. We measured more than 6,000 museum specimens of monarch butterflies collected from 1856 to the present, as well as contemporary wild-caught monarchs from around the world. We determined (1) how wing morphology varies across the monarch's global range, (2) whether initial long-distance founders were particularly suited for migration and (3) whether recently-established non-migrants show evidence for contemporary phenotypic evolution. We further reared more than 1,000 monarchs from six populations around the world under controlled conditions and measured migration-associated traits. Historical specimens show that (1) initial founders are well-suited for long-distance movement and (2) loss of seasonal migration is associated with reductions in forewing size and elongation. Monarch butterflies raised in a common garden from four derived non-migratory populations exhibit genetically-based reductions in forewing size, consistent with a previous study. Our findings provide a compelling example of how migration-associated traits may be favored during the early stages of range expansion, and also the rate of reductions in those same traits upon loss of migration.”
As a postdoctoral fellow at the University of Chicago, Freedman said he is "currently using breeding experiments and DNA sequencing trying to figure out which genes affect migratory traits and behaviors in monarchs. This includes wing traits (shapes and size) discussed in the PNAS paper.”
- Author: Kathy Keatley Garvey
Her topic is "How Does the Time of Eating Affecting Our Circadian Physiology?" Access this form for the Zoom link.
The abstract: "The integration of circadian and metabolic signals is essential for maintaining robust circadian rhythms and ensuring efficient metabolism and energy use. Using Drosophila as an animal model, we showed that clock-controlled feeding-fasting cycles is strongly correlated to daily protein O-GlcNAcylation rhythms, which may represent a key post-translational mechanism that regulates circadian physiology. Our results could shed light on the benefits of TRE (or intermittent fasting) and the extent to which modern human lifestyles contribute to the current epidemic of metabolic disorders."
The host is her major professor, Joanna Chiu, a molecular geneticist and physiologist, vice chair of the UC Davis Department of Entomology and Nematology and a Chancellor's Fellow. Liu is currently working in the Chiu lab as a postdoctoral fellow.
For her thesis, Liu explored the interplay between circadian clock and metabolism in maintaining animal health using Drosophila melanogaster as a model. Specifically, she investigated the regulation of cellular protein O-GlcNAcylation by circadian clock and metabolic signals. O-GlcNAcylation is a nutrient senstive post-translational modification that can alter the structure and function of thousands of cellular proteins. She is fascinated by how circadian biology can be shaped by multiple factors through complex mechanisms. Her long-term goal is to understand how molecular pathways are coordinated temporally to maintain animal health and wellness.
Liu received her bachelor's degree in biological sciences in 2014 from Beijing Forestry University, China. She was a recipient of a CSC-UC Davis Joint Fellowship.
Coordinating the fall seminars is Cooperative Extension specialist and agricultural entomologist Ian Grettenberg, assistant professor, UC Davis Department of Entomology and Nematology. He may be reached at imgrettenberger@ucdavis for any technical issues.
- Author: Kathy Keatley Garvey
The seminar takes place from 4:10 to 5 p.m., Wednesday, Oct. 28. Access this site for the Zoom link. Host is Cooperative Extension specialist and agricultural entomologist Ian Grettenberger, assistant professor, UC Davis Department of Entomology and Nematology. He is coordinating the department's fall seminars.
"The research in our lab focuses on understanding how chemical compounds mediate interactions among microbes, plants, herbivores, and herbivore natural enemies," Helms says. "We combine analytical chemistry and behavioral ecology in laboratory and field-based research to investigate how organisms use chemistry to navigate, communicate, and defend themselves. This seminar will discuss some of our ongoing projects examining how plants and insect herbivores use chemical information from their environment to assess their risk of attack and how herbivore natural enemies use such information to find potential prey."
Helms, an assistant professor, holds two degrees from Pepperdine University, Malibu, Calif., both awarded in 2009: a bachelor of science degree in biology and a bachelor of arts degree in biochemistry. She received her doctorate in ecology in 2015 from The Pennsylvania State University, State College, Penn. While in the John Tooker lab, Helms studied the chemical ecology of plant-insect interactions, especially how plants defend themselves against insect herbivores. She investigated how plants use olfactory cues to predict impeding herbivore attacks and the molecular mechanisms involved.
In addition to the general field of chemical ecology, Helms' research interests include plant-insect interactions, tritrophic interactions, belowground chemical ecology, chemical communication, and plant defense.
Her most recent publications:
Helms, A.M., Ray, S., Matulis, N.L.*, Kuzemchak, M.C.*, Grisales, W.*, Tooker, J.F., Ali, J.G. Chemical cues linked to risk: Cues from belowground natural enemies enhance plant defences and influence herbivore behaviour and performance. Functional Ecology. 33, 798-808 (2019). DOI: 10.1111/1365-2435.13297
Acevedo, F.E., Smith, P., Peiffer, M., Helms, A.M., Tooker, J.T., Felton, G.W. Phytohormones in fall armyworm saliva modulate defense responses in plants. Journal of Chemical Ecology. (2019). https://doi.org/10.1007/s10886-019-01079-z
Yip, E.C., Sowers, R.P.*, Helms, A.M., Mescher, M.C., De Moraes, C.M., Tooker, J.F. Tradeoffs between defenses against herbivores in goldenrod (Solidago altissima). Arthropod-Plant Interactions. 13, 279-287 (2019). DOI: 10.1007/s11829-019-09674-3
For any technical issues regarding the seminar, contact Grettenberger at imgrettenberger@ucdavis.edu.
- Author: Kathy Keatley Garvey
The article, “Genome-Enabled Insights into the Biology of Thrips as Crop Pests,” is published in the journal BMC Biology. It is the work of 57 scientists on five continents.
“This project represents over eight years of work by at least 17 laboratories across the globe,” said Professor Ullman, a former chair of the entomology department and a fellow of the Entomological Society of America and the American Association for the Advancement of Science. Her laboratory worked closely with project leader and first author Dorith Rotenberg of North Carolina State University. Project scientist Sulley Ben-Mahmoud of the Ullman lab is the paper's third author.
The western flower thrips, Frankliniella occidentalis, causes billions of dollars a year in damage worldwide. Native to Western North America and about the size of a pinhead, the insect feeds on a wide array of food, fiber, and ornamental crops and transmits plant viruses that cause significant economic damage.
“The western flower thrips and the viruses it transmits, including tomato spotted wilt virus, is important to California agriculture, causing serious problems for tomato growers, pepper growers and growers of leafy greens,” Ullman said. The tomato spotted wilt virus infects more than 1000 plant species, ranging from tomatoes, tobacco and peanuts to pansies and chrysanthemums.
“This system has been a central element of my research program for over 30 years," Ullman said, "and I am extremely excited to see this important resource made available as a tool to help us understand and control these important pests.”
In their abstract, the authors wrote that the publication should lead to “understanding the underlying genetic mechanisms of the processes governing thrips pest and vector biology, feeding behaviors, ecology, and insecticide resistance.”
“Attaining a tool to unlock the mysteries of western flower thrips biology and interactions with plant viruses in the family Tospoviridae has been a dream of mine through over 30 years of working on this system,” Ullman commented. “The genome project enabled the discovery of salivary gland-enriched genes in this tiny insect that is now guiding work that Sulley Ben-Mahmoud and I are doing with collaborators Dorith Rotenberg, Joshua Benoit, Samuel Bailey and Priya Rajarapu to identify salivary proteins acting as effectors.”
Rotenberg launched the project in 2011 after delivering a lecture at the 5th Annual Arthropod Genomics Symposium in Kansas City, Mo. “At the time, I was very naïve about what it would take to steward a thrips genome project, but was excited about what a genome sequence could mean for those of us interested in the molecular basis of thrips vector competence and thrips pest biology.”
The team worked with the i5k initiative, an international effort to sequence and analyze 5,000 arthropod genomes. This includes insects, crustaceans, spiders and other creatures with exoskeletons, segmented bodies and pairs of jointed legs.
The Rotenberg-led thrips genome project team first developed an inbred line of thrips. Baylor College of Medicine's Human Genome Sequencing Center sequenced and assembled the genome. The Rotenberg team then verified the location of 10 percent of the nearly 17,000 genes and annotated them to better understand what they do.
The authors report that some genes are associated with the thrips' ability to develop and reproduce, to find plant hosts through taste and smell, to protect against pathogens, and to detoxify plant-produced chemicals and insecticides. The latter is of special interest because thrips are known for rapidly building up resistance to chemicals.
Said Rotenberg: “I discovered over the course of eight years that the thrips genome consortium created something much greater than the sum of its parts. I was fortunate to recruit 17 international groups with expertise in arthropod genomics, evolution and development, thrips vector biology and microbe (and virus)-insect interactions to volunteer their time not only to manually correcting and annotating gene models, but to use expression evidence to explore with me new frontiers in thrips innate immunity, lateral gene transfers of bacterial origin, thrips-plant interactions, thrips development and reproduction. These world-renowned experts helped shape the landscape for contemporary molecular and evolutionary studies of Thysanoptera and in my opinion, as important, helped shape the careers of several undergraduates, grad students and postdoctoral scholars involved in the process. I am excited and proud of what we accomplished together.”
Ben-Mahmoud described the research as “a monumental feat, and I am proud of my contributions to it. I have no doubt that the paper will inform and benefit the studies of many other international insect-vector research groups, not only those who work directly with the western flower thrips.”
