To attract a mate, many frog species use multimodal displays, which may include croaking and body and leg movements. Little is known of how selection pressure for these displays may drive evolution of other systems within the body, including androgenic sensitivity.

Mangiamele et al. studied the ‘foot flag’ display of the male Bornean rock frog (Staurois parvus; pictured). Administration of testosterone led to a significant increase in ‘foot flagging’ behaviour. Quantitative PCR showed that the frogs’ hind limb muscles (which produce the display) have significantly higher androgen sensitivity when compared with other closely related species, mediated by an approximately tenfold higher expression of androgen receptor in these muscles in S. parvus.

This implies that ‘foot flagging’ is an androgen-dependent signal, and its recent evolution in this frog species is associated with increased androgen sensitivity in the muscles used to produce it.

Read the full article in Proceedings of the National Academy of Sciences of the USA 113 5664–5669