Biologist Susan Foster and her students study the threespine stickleback in the lab and in the field. These small fish provide big insights into evolutionary biology.
Meet the researchers: Fishy went a courtin’
Interview with Professor Susan Foster, Ronelle Savoie, Melissa-Ann Scotti and Jillian Cadorette-Wishart
Clark biologist Susan Foster has dedicated her research
to understanding the threespine stickleback fish, particularly when it comes to these
fishes’ courting behavior. In this interview, she discusses her fieldwork in Alaska and
Canada, bringing the ocean back to Clark, and how Clark students have helped her along
the way. Clark biology seniors Ronelle Savoie,
Melissa-Ann Scotti, and
Jillian Cadorette-Wishart (all to be participants in Clark's
fifth-year free MA program) contributed to the interview.
What are threespine sticklebacks?
Sticklebacks are single species of fish with a diversity of forms.
The ocean form is an ancient fossil form that hasn’t changed 12 million
years ecologically. Post glacially, that form has given rise to large
number of populations in the Pacific Northwest. I study these derived and
novel populations in fresh water in British Columbia, Canada and in Alaska.
How do you get your specimens?
I go up to Alaska or Canada in the summers and often I take Clark undergraduates
with me. Some years I send undergrads with graduate students to make the
collections. But when I’m doing behavioral fieldwork and not just making
collections, I’m there. Then the collections are sent back to be worked up
for history studies.
What are you trying to find out about these populations?
I want to understand how the first reproduction evolved, how aging evolved
and how these life history features have evolved. If we compare marine
ancestor to derived fresh water forms, we ask ourselves how the environment
has affected the fresh water forms. We use our collections for life history
studies, life history evolution or to understand morphological
(physical shape) changes in the fish. A good example is provided by
Ronelle's research. She's looking at how body shape changes affect drag
(the fish's resistance against the water) and capabilities of fish.
But the piece that is closest to my heart is the behavioral diversification.
I want to understand how differences in behavior have evolved and how those
differences translate into speciation.
What kind of behavior are you looking at?
Courtship behavior. I’m looking at the features a male stickleback uses to
entice females to his nest or territory. In stickleback, that can be very complex.
Courtship behavior includes zigzag dancing and/or a complex action called dorsal
pricking in which the male positions himself spine up beneath the female and as
they move up he pricks his spine into her belly. Usually that’s interpreted as
deterring the female from coming to his nest. But, in fact it’s the only form of
courtship in some populations. We think the way in which these differences in
courtship appear in different populations influences female choice and the probability
that the nest will be detected when attacked by big groups of cannibalistic stickleback.
Can you actually study that courtship behavior in the lab?
Yes. We study it here in the lab. Melissa and Jillian have both worked on this
with me. What we’re finding out is that in the field, you get very different
patterns of courtship behavior than in the lab. In the field, in populations
where there are cannibalistic groups of sticklebacks, courtship behavior is
inhibited. That is, females encounter reserved courtship behavior. But if
you bring them into the lab, where there are no cannibalistic groups, two things happen.
The males become brighter red in color, and courtship is more vigorous.
We have a difficult time getting them to mate when we bring them into the lab because females are experiencing
behavior patterns that are well outside their normal repertoire or ones they have come to prefer. What’s equally interesting is looking at the males. When we bring them in lab, it’s the male who has to change his
behavior. In fact we just applied for a new grant to address that questions very specifically across a set of
How do the cannibalistic groups you mentioned behave?
Females are interested in reproduction about 1 day in 10. So they breed, lay eggs, feed and return. In cannibalistic populations, they are feeding in large groups on the bottom of the ocean. These are the same ones that attack nests.
So it’s possible for females to attack a nest of their own eggs. I guess they’re thinking ‘If someone is going to consume
these eggs, it might as well be me. I can use this food to help me lay other eggs.’
Ronelle, you're working on another research project about the sticklebacks. Can you describe it?
I’m working on a project about drag. Drag is the resistance the fish has as it swims through water. I’m taking measurements of the fish, measuring abdomen width, height, the head of the fish and comparing those measurements across gravidity
(pregnancy) stages of females because their abdomens swell. We want to understand how that actually affects the drag that the fish incurs. After we figure out how much that changes gravidity levels, we’re also going to compare our results to the marine stickleback and see if drag has impact on its swimming speed.
How are Clark students helping with the research?
Susan: We have seven undergraduates involved in research. It works in two separate ways. As I mentioned earlier, we train them to make collections when we go to Alaska. But what’s really nice about Clark is that I have students who have worked with me for several years.
Melissa: I’ve been doing research with Susan since the summer after sophomore year. I decided that this is what I wanted to do. I just asked Susan if I could work with her and she said
yes, and I was allowed to do it. Right now, I’m working on different populations of
stickleback found in Alaska. We brought them back here and let them set up nests in
individual tanks. Then we introduced a model of a male stickleback. I've been recording
the reactions to the model. Do they ignore it, bite it? And is there a difference in the
way the different populations react? Then I analyze these results using a computer program.
Jillian: I’ve been working on trying to see how the startle response differs between different
stickleback. Using our big tanks and making a vibration on the tank, we’re measuring how the fish will jump. It can show us how
the fish might react to predators.
Susan: And now Melissa, Jillian, and Ronelle are going into Clark’s fifth-year Master’s program. The work they are doing is related to the work I do, but in each case, they have selected projects that interest us and can help us, but also that they can publish in the end. That helps
Clark's entire research program.
|Left top and bottom: Susan Foster; top right: Jillian, Melissa-Ann, and Ronelle; bottom right: Jillian.