Dynamic sexual dichromatism produces a sex signal in an explosively breeding Neotropical toad: A model presentation experiment

Breeding biology and the evolution of dynamic sexual dichromatism in frogs

“…Yellow coloration is typically brighter relative to background environments; therefore, in species that are active in low‐light conditions, increased brightness of yellow frogs may serve as an effective achromatic signal. For example, males in the dynamically dichromatic yellow toads ( I. luetkenii ) distinguished between brown and yellow clay frog models in both daytime and night‐time trials (Rehberg‐Besler et al ., ), indicating that sexual differences in hue and/or luminance were detectable in low‐light conditions. The high prevalence of yellow coloration in dynamically dichromatic frogs may also reflect physiological limits as to which temporary colour changes are possible.…”

“…Female choice is often cited as an evolutionary mechanism in sexually dichromatic vertebrates when males are the ‘brighter’ sex (Salthe, ; Andersson, ; Kodric‐Brown & Brown, ; Wiens et al ., ; Cooper & Hosey, ; Todd & Davis, ; Caro, ) and is a more common component of courtship in frogs with prolonged breeding than in those with explosive breeding (Wells, ). Therefore, whereas behavioural studies and observations in dynamically dichromatic frogs indicate that temporary sexual colour differences serve as intrasexual signals (Wells, ; Sztatecsny et al ., ; Rehberg‐Besler et al ., ), ontogenetic (permanent) colour differences, which are subject to natural and sexual selection year‐round, may be more likely to serve as intersexual signals of mate quality (Vásquez & Pfennig, ; Maan & Cummings, ). Hylid genera with monochromatic, dynamically dichromatic and ontogenetically dichromatic species ( Scinax, Dendropsophus and Hypsiboas ) present an ideal opportunity to address these hypotheses with natural history observations of courtship behaviours (e.g.…”

“…Behavioural studies in two explosive breeding species with dynamic dichromatism (Fig. ), the European moor frog ( Rana arvalis ) and the yellow toad ( Incilius luetkenii ), indicate that temporary divergence in coloration between the sexes prevents costly mistakes in sex recognition when males seek females in aggregations with male‐biased operational sex ratios and scramble competition for mates (Doucet & Mennill, ; Sztatecsny et al ., ; Rehberg‐Besler et al ., ). Similarly, in lek‐breeding stony creek frogs ( Litoria wilcoxii ), yellow coloration in males during amplexus serves as an intrasexual signal that may diminish sperm competition or displacement by other males (Kindermann & Hero, ).…”

“…In many species with neurophysiologically mediated dynamic colour change, such as chameleons, conspicuous display coloration has evolved for social reasons via sexual selection and dynamic colour change allows animals to respond to a social or predatory cue by adjusting their signal according to a potential receiver's visual system (Stuart‐Fox et al ., , ; Stuart‐Fox & Moussalli, ). By contrast, dynamic colour change in frogs is slower because it is hormonally mediated (but see Kindermann et al ., ) and is typically studied in the context of camouflage and thermoregulation (Camargo et al ., ; Tattersall et al ., ); however, studies in species with ephemeral colour differences between the sexes (dynamic sexual dichromatism) indicate that dynamic colour change in frogs may also evolve for social purposes via sexual selection (Wells, ; Ries et al ., ; Doucet & Mennill, ; Sztatecsny et al ., , ; Rehberg‐Besler et al ., ; Kindermann & Hero, ).…”

Porphyrins produce uniquely ephemeral animal colouration: a possible signal of virginity

“…Slight daily colour changes have also been reported in zebrafish, Danio rerio , that coincide with mating events13. Despite our limited understanding of rapid alterations in colour states, these traits may experience strong sexual selection pressure if they signal to potential mates information about an individual’s breeding status that is only available during a very short period of time1415. Expression duration, therefore, may be an overlooked factor influencing the information content and thus the evolution of animal colouration.…”