title: Increased androgenic sensitivity in the hind limb muscular system marks the evolution of a derived gestural display.
abstract: Physical gestures are prominent features of many species' multimodal displays, yet how evolution incorporates body and leg movements into animal signaling repertoires is unclear. Androgenic hormones modulate the production of reproductive signals and sexual motor skills in many vertebrates; therefore, one possibility is that selection for physical signals drives the evolution of androgenic sensitivity in select neuromotor pathways. We examined this issue in the Bornean rock frog (Staurois parvus, family: Ranidae). Males court females and compete with rivals by performing both vocalizations and hind limb gestural signals, called "foot flags." Foot flagging is a derived display that emerged in the ranids after vocal signaling. Here, we show that administration of testosterone (T) increases foot flagging behavior under seminatural conditions. Moreover, using quantitative PCR, we also find that adult male S. parvus maintain a unique androgenic phenotype, in which androgen receptor (AR) in the hind limb musculature is expressed at levels ∼10× greater than in two other anuran species, which do not produce foot flags (Rana pipiens and Xenopus laevis). Finally, because males of all three of these species solicit mates with calls, we accordingly detect no differences in AR expression in the vocal apparatus (larynx) among taxa. The results show that foot flagging is an androgen-dependent gestural signal, and its emergence is associated with increased androgenic sensitivity within the hind limb musculature. Selection for this novel gestural signal may therefore drive the evolution of increased AR expression in key muscles that control signal production to support adaptive motor performance.
authors.affiliation: Department of Biological Sciences, Smith College, Northampton, MA 01063;
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Mangiamele
authors.affiliation: Department of Biology, Wake Forest University, Winston-Salem, NC 27109; mfoxhunter@gmail.com.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Fuxjager
authors.affiliation: Department of Biology, Wake Forest University, Winston-Salem, NC 27109;
authors.forename: Eric R
authors.initials: ER
authors.lastname: Schuppe
authors.affiliation: Department of Biological Sciences, Smith College, Northampton, MA 01063;
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Taylor
authors.affiliation: Department of Integrative Zoology, University of Vienna, A-1090 Vienna, Austria;
authors.forename: Walter
authors.initials: W
authors.lastname: Hödl
authors.affiliation: Department of Integrative Zoology, University of Vienna, A-1090 Vienna, Austria; Vienna Zoo, A-1130 Vienna, Austria.
authors.forename: Doris
authors.initials: D
authors.lastname: Preininger
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D005868:Gestures; D006614:Hindlimb / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D011898:Ranidae / Q000502:physiology*; D011944:Receptors, Androgen / Q000032:analysis / Q000502:physiology; D012726:Sexual Behavior, Animal; D013739:Testosterone / Q000494:pharmacology*; D014828:Vocalization, Animal
chemical_list: D011944:Receptors, Androgen; D013739:Testosterone
keywords: androgen receptor; courtship behavior; frogs; signal evolution; testosterone