Steve Hendrix is a professor in the University of Iowa’s Biology Department. He is also a CGRER member, and recently received a seed grant from the organization. One of the focuses of Hendrix’s research is on bees – specifically, the possible decline of wild solitary bees. Hendrix discussed this research with the Iowa Environmental Focus.
How Professor Hendrix first got involved in plant-animal interactions:
“When I was a graduate student I took a graduate seminar in which I reported on a recent finding of insect molting hormones in plants, specifically in ferns. I was just fascinated by the fact that there could be plants that could produce these hormones. Then people immediately said that [the hormones] must be a defense against insect attacks. I just got really caught up in this topic, and I did my PhD research on whether or not molting hormones acted as a chemical defense against insects [note: it was determined that the molting hormones do not act as a defense]. From there my interests just blossomed. I got very interested in the affects of insects on plant fitness – an evolutionary point of view because so few studies on natural systems had been conducted.
“So, I spent a number of years working with one particular model system of a wild plant, and I determine what the effects of an important herbivore was on fitness. Then I was interested in working on prairies, so I decided that I would look at insect herbivores in prairies because I was starting to get interested in habitat fragmentation. The rise in conservation ecology in the late 80’s and early 90’s certainly stimulated this interest. I started looking at plant-herbivore interactions in fragmented prairies. That led me to the realization that the problems that prairie plants had in small populations with respect to reproduction, were because they didn’t attract pollinators. So, their seed production was down because the insects weren’t there to complete the reproductive process. That got me interested in pollinators, and when you’re interested in pollinators and prairie plants, then you’re by definition interested in bees.”
His research in determining whether or not wild solitary bee populations are declining:
“What we’re trying to do is really address two questions. One of them is a rather big question, and that is ‘are there declines in wild solitary bees, like we see with honey bee colonies’? For most people, when you say ‘bees’ they’re going to think of honey bees, which are social and can have colonies of 10-30,000 individuals. In addition to that one species, there are about 20,000 species of solitary bees. They’re called solitary bees because each female in these 20,000 species makes her own nest in the ground or in cavities of plant stems, and will go out and gather pollen from plants, which she will pack into a cell underground. She then will lay an egg on top of it, seal the cell off and repeat the process. She will do this as many times as she can during her lifespan, which can be anywhere between 2-4 weeks . . .
“We just finished a study with an honor student here in the lab where we looked at pollination of crops at produce farms in east-central Iowa. What we found was that the solitary bees were doing the bulk of the pollination of those crops. About 90% of the bees that we caught were wild solitary bees. Even the places where there were honey bee colonies relatively close, it wasn’t the honey bees doing most of the work. So, [solitary bees] are very important in terms of local farming efforts. They’re also very important to crops that are distant from us like almonds in California, where they’re now actively investigating the use of other bee species besides the honey bees in pollinating the almond crop. So, the solitary bees are very important, and what people are worried about is that the solitary bees are under a lot of stress just like the honey bees are. But nobody knows, or has the data, to answer the question: ‘are the solitary bees declining’?
“We have data from seven prairie preserves from about a decade ago where we very carefully measured the diversity of the bees at these prairie preserves. What we’re now doing is re-measuring the diversity at these seven sites, and we’ll be able to statistically compare the results we get this year with those that we got a decade ago, and answer the question, ‘is there or is there not a decline in the diversity and abundance of solitary bees’? The difficulty is that the measurement of diversity that you get – the actual numerical value – is highly dependent on how much effort you put into searching. So, when you spend a week on a prairie you’ll get one diversity measurement, but if you spend two weeks on a prairie you’ll get a different figure. Our study is unique because not only are our methods identical in terms of the time sampling and the size of the area we’re sampling, but we’re actually sampling from the same exact plot. Up to now the only data that we have that addresses the issue of the loss of solitary bees are a number of studies that I would term as ‘failure to find’ studies. For example, if people go out and look for bumble bees in England, and they report that they cannot find these species, the implication is that they may be gone, but we don’t know for sure because it’s just a failure to find. That data is alarming, it’s not a good sign, but it’s not a statistical test.”
The other part of the research, where Professor Hendrix is trying to determine if RNA viruses are present in wild solitary bees:
“The other question we want to answer is ‘if there’s a decline, are the RNA viruses that have been implicated in colony collapse disorder in wild bees as well’? . . . We don’t know anything about these RNA viruses connected with wild bees. One report came out around December saying that there were some instances of RNA viruses in a few species of wild bees in Pennsylvania and Illinois, but we don’t know anything else about it. We think the virus may be transferred from honey bees to wild bees via flowers, but we don’t know what the array of these RNA viruses might be in wild bees. It could be that there are lots of RNA viruses in solitary bees and nobody ever really looked. It may be that RNA viruses are present, but they’re all asymptomatic in wild bees – that is, you can’t tell [that they’re carrying the viruses]. So, we’re collecting 10-15 different species of solitary bees at different sites to look for the RNA viruses.”