Data from: Social effects on fruit fly courtship song

Courtship behaviour in Drosophila has often been described as a classic
innate behavioural repertoire, but more recently extensive plasticity has
been described. In particular, prior exposure to acoustic signals of con-
or heterspecific males can change courtship traits in both sexes that are
liable to be important in reproductive isolation. However, it is unknown
whether male courtship song itself is socially plastic. We examined
courtship song plasticity of two species in the Drosophila melanogaster
subgroup. Sexual isolation between the species is influenced by two male
song traits, the inter-pulse interval (IPI) and sine song frequency (SSF).
Neither of these showed plasticity when males had prior experience of con-
and heterospecific social partners. However, males of both species
produced longer bursts of song during courtship when they were exposed to
social partners (either con- or heterospecific) than when they were reared
in isolation. D. melanogaster carrying mutations affecting short- or
medium-term memory showed a similar response to the social environment,
not supporting a role for learning. Our results demonstrate that the
amount of song a male produces during courtship is plastic depending on
the social environment, which might reflect the advantage of being able to
respond to variation in intrasexual competition, but that song structure
itself is relatively inflexible, perhaps due to strong selection against
hybridisation.