The hot and cold of butterfly dancing

Hypothesis: courtship behaviour in squinting bush brown butterflies ( Bicyclus anynana) is related to the climate they experienced when they were mere caterpillars

I stumbled across a very interesting piece of work that I plan to write about (just as soon as I get my hands on the paper). Two researchers, Kathleen Prudic and Antónia Monteiro, at Yale University were curious as to why both male and female squinting bush brown butterflies, Bicyclus anynana, sport attractive spots on their wings -- a character that is usually reserved for males who do the courting. They found that when the caterpillars (larvae) were raised in warmer and wetter conditions, the male butterflies performed mating dances to attract females. But when butterflies developed in drier, cooler temperatures, it was the females who danced for the males.

In some animals, males and females look the same, even developing the same sexual ornaments (wing spots in butterflies, for example). There are several hypotheses to explain why sexual ornaments are found in both sexes. These hypotheses include genetic correlation, same sex competition, and mutual mate choice.

But this hot-off-the-presses study finds that one particular butterfly species, endemic to parts of Africa, shows developmental plasticity in their mating behavior based on the temperatures they experienced when they were caterpillars. In short, males did the courtship dancing when they were raised at warmer temperatures, whilst cooler temperatures made the females into the dancers: the "choosy sex" depends upon climate. So in this situation, there is selective pressure on both sexes to develop and maintain sexual ornaments -- spots on their wings.

As a result of their work, the authors propose another hypothesis for why sexual ornaments are found in both sexes: reciprocal selection.

If you follow the link to the reference, you can stare longingly at the paywalled paper:

Kathleen L. Prudic, Cheonha Jeon, Hui Cao and Antónia Monteiro. Developmental Plasticity in Sexual Roles of Butterfly Species Drives Mutual Sexual Ornamentation. Science (7 January 2011) Vol. 331 no. 6013 pp. 73-75 DOI: 10.1126/science.1197114