Alonzo discusses fish reproduction, parenting

Amongst the Mediterranean wrasse — fish that are found in shallow, coastal waters — stay-at-home dads get all the love, and the deadbeats get none.

Ecology and Evolutionary Biology professor Suzanne Alonzo delivered her talk, “Games Fish Play: The Effect of Conflict Within and Between the Sexes on the Evolution of Reproductive Behavior,” Feb. 4 as part of the Yale Institute for Biospheric Studies/Environmental Science Center Friday Noon Seminar Series. She said females choose males to mate with based on past mating success, as past success is a good indicator of whether that male will provide parental care. Approximately 50 people, mostly graduate students and professors, attended the lecture, filling the large classroom on the first floor of the Environmental Science Center.

Alonzo explained that some researchers believe reproductive strategies are determined only by resource distribution, while others believe they are determined by sexual conflict. Alonzo said she believes both theories ignore the importance of the other, so she is trying to develop a cohesive theory of reproductive strategies.

“My work is a combination of empirical and theoretical approaches,” Alonzo said. “We’re trying to explain what we observe in the natural world.”

Alonzo works at a research station affiliated with the University of Liege in France, where she studies the Symphodus ocellatus, a Mediterranean wrasse. The males of this species, Alonzo said, come in two varieties — nesting males, who are large and provide parental care, and sneaker males, who are small and leave a nest after they spawn.

Alonzo said her research indicated females choose both nesting locations and mates based on past mating success. Consequently, females try to avoid mating with sneaker males. This method of choice provides a cycle whereby males become either very successful or very unsuccessful. Alonzo said some unsuccessful males will attempt to take over other males’ territories, and success in takeover loosely correlates with size.

Mark Urban FES ’07 said he admired Alonzo’s approach to research.

“She’s got a really interesting research system,” he said. “She combines both really rigorous theory and experiments and observation of natural systems.”

In one of her experiments, Alonzo threw a net over a highly successful male, eliminating it from the pool of possible mates. She found this tactic could increase the reproductive rates of fish with low but non-zero success rates.

“It’s possible to transfer mating success,” Alonzo said. “A male with a low spawning rate can become high-success if his high-success neighbor, for some reason, becomes unavailable.”

She said one of the more surprising results of her studies was that past mating success is the only noticeable trait that interests females. Female wrasses are not attracted to males by size, color or age, and they do not consider site, orientation or depth when choosing nesting locations.

“Conflict over parental care may be trumping female choice for other, heritable traits,” Alonzo said.

It is still unclear, she said, why females initially choose certain males, creating small discrepancies in spawning success that are exacerbated through the cycle.

Alonzo said her studies, while species-specific, have implications beyond the Mediterranean wrasse. Interactions between individuals are at the heart of many ecological and evolutionary processes, she said. Specifically, conflict over parental care is relevant to the reproductive behavior of most species.

Adrian LeCesne ’08, one of the few undergraduates who attended the lecture, said he was impressed by Alonzo’s research methods.

“She took into account most of the behaviors of the fish and was discrete enough not to disturb the fish,” he said.

Comments