Boarding pass: deciphering the travel habits of “Mite-y” nectar thieves


Humans aren’t the only flightless creatures who have found a way to fly in order to get around. Mites, some as tiny as the dot on that “i,” roam the rainforest they call home, hitchhiking on hummingbirds that serve as living, breathing airplanes.

Hummingbirds roam around nectar-stealing and hitchhiking mites that are harmless passengers – except when it comes to taking more than their fair share of nectar from certain flowers, says Ecology and Evolutionary Biology Ph .D. Student Laura Bizzarri, who was very interested in these small jet-setters during his studies. Bizzarri recently received the Alwyn Gentry Prize awarded by the Association for Tropical Biology and Conservation For his work.

“I certainly didn’t intend to come to college with the idea of ​​studying mites,” says Bizzarri. “As soon as my advisor, Carlos Garcia-Robledo, mentioned that these mites were hitchhiking on hummingbirds, I thought, ‘Yes, that sounds very interesting.’ I started doing some background research, and it wasn’t hard at all to like them. There are so many unexplored questions about these mites.

Mites begin their journey by crawling aboard a hummingbird’s beak and later land on a flower to feed on the nectar. Bizzarri explains that in a sense, mites are real stingers in that they don’t benefit flowers by pollinating them like hummingbirds do, which is why mites are called “nectar stealers”. Do they have flower preferences? Do we need more than one flight to get to my destination? How do they know when it’s time for a layover? Wanting to answer these questions and more about mite travel habits, Bizzarri realized that it might be useful to draw on research into human travel behaviors.

“A lot of research has been done on the geography of human transport and the accessibility and efficiency of human transport hubs,” says Bizzarri. “For example, how easy it is to get from one airport to another, or from one metro station to another, so from there I started doing some research to try to determine if there were simpler methods already developed for human transport. “

Bizzarri discovered a method flexible enough to be applied to the study of mites.

“The method can be used to measure direct ways of connecting different transport poles, but also indirect,” says Bizzarri. “For example, if people have to stop or stop at an airport to get to their destination. This data can be incorporated quite easily into a matrix or table to determine if it is limited in the host plants they use by the hummingbirds they climb on.

To carry out the research, Bizzarri collected more than 10,000 mites over a six-month period. She then used DNA bar coding methods to sort the mites into groups of species.

“Because I had information about where these mites had been sampled, I also had information about the plant species with which these mites interact. Then I used GoPro cameras to record the hummingbirds visits to the plants and this allowed me to identify the hummingbird / plant interactions.

With data on flower transport centers, hummingbird flight routes, and mite passenger travel routes, the next step was to enter the data into a model to study how the components interact. Much like many humans, Bizzarri discovered that mites tend to prefer direct flights over stopovers.

“We found about 18 species of mites and of these, 15 use direct transport routes where they only need one species of hummingbird to get to another of their host plants,” explains Bizzarri. “The remaining three species use a certain percentage of indirect paths, which means that if they are to get from one host plant to another specific host plant, they have to stop at an intermediate plant while using at least two species. different hummingbirds to complete their journey. . “

Bizzarri says that the three species of mites that depend on indirect transport could possibly get anywhere via the hummingbird, and that there is likely a mechanism they use to recognize their host plants.

“And that’s actually part of what I’m looking to do in my PhD, to understand what mechanisms may be responsible for the choice of the host plant for some of the mites.”

Bizzarri is eager to continue studying these tiny creatures and intends to expand the model to study mites that cling to beetles.

“One of the most interesting things about mites is that they are probably one of the most diverse groups of arthropods and arachnids, but because they are so small, they haven’t been studied as much. than other arthropod groups, ”Bizzarri explains. “There’s probably so much unknown about dust mites, and it’s so cool. Modern technology allows us to work on smaller things now, so there is a lot of potential.

Watch a hummingbird visit a flower, taking tiny passengers (courtesy Laura Bizzarri):

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