With funding from the National Science Foundation (NSF), a group of biologists, engineers and climate scientists from Penn State (USA), University of Kansas (USA), Universidad Militar Nueva Granada (Colombia), and Pontificia Universidad Católica del Perú (Peru) launched a summer research program for undergraduate students to help shed light on how pollinators and pollination are responding to our changing world. In 2021, the program was offered virtually to 12 students from the USA, Colombia, and Peru. One of the unique characteristics of this program is that it brings together teams from biological sciences and engineering to find answers to these questions. Why is this an advantage? A major challenge for biologists to understand how pollinator populations are responding to changing climates is that we don’t have instruments that allow us to understand the behavior and physiology of small organisms that move very fast like bees.

Our team of students and mentors in 2021 was set up to answer the following questions:

1. How will increasing temperatures affect pollinator foraging?

2. How do air pollutants affect floral scents and pollinator foraging behavior?

3. How will heat stress on pollinator-dependent crops impact food supply in cities where the largest concentrations of human populations are found?

 

To investigate question 1, Maren Appert and Abigail Jiménez from California (USA), Alonso Delgado from Texas (USA), and Andrés Herrera and Ruben Martín from Cajicá (Colombia) collected foraging data of pollinators along with the varying temperatures of the day and set up bioassays to quantify the critical thermal maxima (CTmax) of pollinators that were foraging during the coolest and hottest parts of the day. The hypothesis they had was that pollinators foraging during the hottest parts of the day would tolerate higher temperatures during the CTmax bioassay. Because these students were working from home, some of them had to set up experiments in their kitchens or get very creative to have the experimental set up working in their backyards. Some students even had their kids as their field assistants. In collecting the empirical data to test their hypothesis, they collected CTmax data from several types of pollinators (bees and flies), and from females and males. The preliminary results of their experiments have reached some interesting findings: (1) some bee species (like honey bees) have significantly higher CTmax than most other bees and flies; (2) males tend to have higher CTmax than female bees, and (3) bees that exhibit higher CTmax generally forage during hotter times of the day. To learn more about their projects and findings, please visit and watch this video.

For question 2, students aimed to understand how air pollutants affect pollinator foraging patterns. This project had two parts. Part 1 focused on developing numerical models to understand how floral scents degrade with environmental pollutants. Part 2 focused on developing radars that could be used to study how changes in floral scents can impact pollinator foraging. In this project, Renata Proano and Tatiana Terranova from Pennsylvania (USA), and Luis Ocupa and Juan Tello from Lima (Peru) worked together. Renata, Luis, and Juan studied the rate of destruction of the most abundantly floral scents (linalool, limonene, β-myrcene, and geraniol) of Geranium Graveolens in urban and rural regions of Pennsylvania. Results from their project indicate that air pollutants modify the quantity and the quality of floral scents leading to floral scents not traveling the necessary distance needed for insect pollinators to locate flowers. However, to appropriately study how air pollutants change pollinator foraging patterns, it is necessary to develop devices that will allow us to characterize foraging behavior. To achieve this goal, Tatiana worked on analyzing radar data to characterize the foraging patterns of bees. Using the programming language python, she was able to develop a program to interpret radar data into realistic foraging flights of bees. To learn more about the projects developed for question 2, check out the two videos below.

Students Alonso Zevallos and Rocio Beneito from Florida (USA) and Yannet Quispes from Lima (Peru) worked on questions 3. Their project aimed to quantify the pollination footprint of populated regions throughout the United States under the scenario of future rising temperatures (i.e., heat stress/waves) to determine how these regions would be impacted by a shortage of pollination dependent crops. For this project, students chose cabbage, soybean, sweetpotato, squash, and cucumber as model crops, and regions of the United States associated with the consumption of these commodities under the probability of increased ambient temperature. Students used publicly available production data and existing pollination field studies and quantified pollinator-dependence of these model crops on insect-mediated pollination services in several U.S. regions. Overall, their results indicate that as temperature rises, the pollination footprint for both consumption and production decreases. In addition, their data suggests that as temperatures begin to rise, pollination footprint will drop, decreasing the supply of pollinator-dependent commodities as demand for these in many U.S. regions increase due to increasing population pressure. These findings imply that there is an urgency to take action to stop these rising temperatures.

Despite the pandemic, our 2021 iRES virtual program facilitated the collaborative work of students and mentors from 9 institutions in 3 countries. All students’ projects generated novel scientific findings and benefited from the interdisciplinary interactions of scientists in different fields. Our results indicate that our changing world is impacting pollinators in multiple ways and that changes in pollinator foraging behavior, their ability to fly under high temperature and to respond to changes in the plants may significantly disrupt plant-pollinator interactions and our food systems. We are hoping the next 2 years of this project will continue to generate valuable data to understand how pollinators are responding to all of these ongoing environmental changes linked to human activities.

Project funded by NSF and is administered by the López-Uribe Lab in the Department of Entomology at Penn State University.

Contributed post by

Margarita M. López-Uribe

Assistant Professor in Pollinator Health

Pennsylvania State University

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