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Interview with Professor Todd Livdahl
Ecologist Todd Livdahl's lab is one of several in biology where undergraduates can participate
in research. In a recent interview, he talked about his mosquito research.
How did you become interested in biology and ecology?
I knew that I wanted to go into some kind of quantitative science. I started off thinking about physics, since I'd grown up in a physics family, but that didn't really appeal to me too much. Then I became interested in biology. That was in the late 1960s when there was a lot of awareness about environmental problems. Ecology seemed like an area that was going to be growing fast, and where I might be able to apply more of my mathematical interests than in straight biology. A course in environmental science early on was instrumental in convincing me that my interests lay there.
What is ecology?
In the textbooks ecology is narrowly defined as the study of the distribution and abundance of organisms. But of course, many ecologists have much broader interests than that. They're interested in environmental problems, evolutionary biology, and so on. A broader definition might be the study of organisms and how they interact with the environment.
So ecology can encompass anything from the study of microorganisms to the study of human beings?
Yes. Ecology is studied from various points of view. It can be studied at the ecosystem level, working at a really large scale. Quite often it's done from the point of view of a single species, and the interactions that influence whether that species will be successful or unsuccessful in a particular situation.
What is your own research focus?
I'm interested in the evolution of life histories; that is, the study of any feature that influences the timing or the amount of survival and reproduction, and this includes rates of growth and development Also, I study the properties that organisms have that influence population growth. I also try to unravel species interactions and make predictions about the outcome of biological invasions. In order to study these problems I've chosen to work with container-breeding mosquitoes. They live in small, simple habitats that can be manipulated experimentally. There are a lot of things that you can do with mosquitoes that you can't with other types of organisms.
So you can observe mosquitoes in an environment that you create in the lab, as well as in the field?
Yes.
Is it correct that we humans are inadvertently creating breeding grounds for mosquitoes?
Yes, we are. In particular, we create tire habitats. A discarded tire filled with rainwater has a lot in common with treeholes, the preferred habitats of the types of mosquitoes I study. A tire sitting on a forest floor in a shady place is a perfectly good place for these mosquitoes to lay their eggs. Humans are adding about 200 million tires to the landscape each year, so that provides a lot of places for mosquitoes to breed. We've also been importing used tires from various parts of Asia, particularly Japan. Tire importation has resulted in the introduction of a new mosquito species (the Asian Tiger mosquito or Aedes albopictus to North America, a species that has been a severe public health problem in much of Asia and the Pacific Islands.
That situation sounds like a product of economic globalization.
We like to think of recycling as an environmentally friendly thing to do, but in this case these tires were brought in for recycling purposes. We have to keep in mind that when we move things around the globe, we quite frequently move organisms around as well, some of which can be dangerous.
How do you study the life pattern of mosquitoes?
As an example, we have a particular interest in egg-hatch delay. Of the mosquitoes that live in small containers, the most successful seem to have some way of delaying the hatch of some of their eggs. We think this is in response to the problems presented by living in a small container that might dry out frequently. Normally, eggs hatch after rainwater covers them. By having some eggs refrain from hatching after rainfall, that is, by essentially creating a "bank" of unhatched eggs, mosquitoes might be able to hedge their bets in an environment where rainfall is erratic.
We hatch eggs in vials, put them in nutrient broth for 24 hours and see how many of them hatch. Then we raise the larvae in petri dishes and measure how long it takes them to reach the next stage of development--the pupa.
Do you vary the size of the containers or how often they receive water?
Actually, we vary the density of the larva. By doing that we can quantify how sensitive the population is to crowding, as well as do comparative studies among different populations.
We've done this kind of work with the invading Asian Tiger mosquitoes that came in on the tires and the native treehole mosquitoes. We've studied the latter most intensively since it's native to this area. We've also collected this mosquito from 23 different populations between New Jersey and Georgia to see if egg hatch delay has any relationship to precipitation patterns. So we've been looking at a fairly wide variety of different rainfall situations.
Does that mean that mosquitoes don't live in really dry areas?
They're less of a problem in regions without much water. But there are mosquitoes that live in rock pools in the desert. Mosquitoes have managed to find a way to succeed in an impressive variety of environments.
What kind of containers do you keep the adults in?
In mesh cages, about 1 cubic foot in size. We provide them with food, a flask of sugar water for them to drink, and a cup to lay their eggs in.
Is there an opportunity in biology for undergraduate students to participate in research?
Yes. There are ample opportunities. I'm always happy to welcome undergrads into my lab.
The best approach is just to knock on professors' doors and talk to them about what they're doing! A student can do a bit of background checking on the research interests of a faculty member, or talk to the teaching assistants in the intro courses about what they're doing. All of us are interested in having undergraduates work in our labs and most of us are interested in doing it as early in a student's program as possible.
So students don't have to wait until their senior year?
Certainly not. I think a project is much more likely to succeed if it has more than one semester or year of work put into it. So the earlier students can get started, the more likely they are to produce something meaningful.
Does biology offer a Ph.D. program as well?
Yes, so if students find faculty intimidating, they can get to know the grad students and work their way into the lab that way. But the faculty aren't that intimidating!
What do you think that Clark offers the student who wants to study biology?
What we offer is ample opportunity to do research projects at a wide variety of levels. They can be closely guided research projects or independent projects--we're receptive to a lot of different approaches that students might want to take. We provide them with the opportunity to work closely with faculty, which I think is an unusual opportunity for undergrads at research-intensive institutions, because most are much larger than Clark. We give them lots of personal attention, and we get good work out of them, quite often resulting in a publication