Species Description: Guayasamin JM, Krynak T, Krynak K, Culebras J, Hutter CR 2015 Phenotypic plasticity raises questions for taxonomically important traits: a remarkable new Andean rainfrog (Pristimantis) with the ability to change skin texture. Zool J Linean Soc 173: 913-928.
This species is easily diagnosed in life as it has the ability to interchange its skin texture from tuberculate to smooth, which is a trait found in only one other frog species, P. sobetes. In preservative, it can be diagnosed from a combination of the following characters: coarse skin punctuated with tubercles; presence of dorsolateral folds; tympanum present and partially covered on top by a supratympanic fold; smooth truncate snout; conical tubercle present on upper eyelid; vocal sac in males; no nuptial pads in males; Finger I shorter than Finger II; lateral fringes on fingers and toes; conical tubercle on heel; no toe webbing; Toe V longer than Toe III; enlarged circular toe tips. It is similar in appearance to P. verecundus, though P. verecundus differs in having short dorsolateral folds that don’t extend past the sacrum (versus long dorsolateral folds that extend past the sacrum in P. mutabilis), a V shape on the throat of females, and the slightly larger size in males. It is similar in appearance to P. sobetes and shares the ability to change its skin texture, though P. sobetes differs in males being significantly larger than the females, having a bright red iris with no stripe (versus a light old iris with a red stripe in P. mutabilis), and lacking red flash coloration near the vent or the underside of the thighs (Guayasamin et al. 2015).
In life, the back is light brown to grey green, with bright green markings and grey or brown V shaped patterns that are bordered by a fine white line. The dorsolateral folds are orange. The underside is light grey to brown and has darker spots, as well as some smaller white spots. The iris is creamy to golden and has a fine black netted pattern as well as a red horizontal streak. The underside of the thighs and the groin is red. In preservative, it has a light brown to grey back, with dark V shaped patterns that are bordered by a fine white line. The dorsolateral folds are light pink. There are dark diagonal stripes on the limbs and sides of the body (Guayasamin et al. 2015).
The skin texture is highly variable in live specimens, as this species is able to change its skin from tuberculate to smooth depending on conditions in its environment (Guayasamin et al. 2015).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
Males were heard calling during January and February 2013. Three distinct calls are made. The first type was a single note that sounded like a short ring and is composed of one modulated pulse with a robust amplitude and 2 - 4 modulated pulse with weak amplitudes. The call does not have frequency modulation and has a pulse rate of 0.041 - 0.11 pulses per ms, a call duration is 45.7 - 49.0 ms, and a dominate frequency between 3273 - 3359 Hz. The limits of the fundamental frequency are 3255 - 3346 Hz for the lower limit and 3617 - 3708 Hz for the upper limit (Guayasamin et al. 2015).
The second type consisted of a single screech-like pulsed note composed of two or more robust and many weak amplitude modulated pulses. This call also is not frequency modulated and has a pulse rate of 0.138 - 0.274 pulses per ms, a duration of 68.0 - 99.0 ms, and a dominate frequency of 3358 - 3445 Hz. The limits of The limits of the fundamental frequency are 3256 - 3345 Hz for the lower limit and 3708 - 3799 Hz for the upper limit (Guayasamin et al. 2015).
The third type consisted of a series of 5 – 6 long trill-like calls broken by short intervals between each and increasing in frequency with each successive call. The duration of the series of calls is 301.0 - 456.0 ms with a 4.2 - 7.3 second interval between series. Individual calls have a single robust modulated pulse and many weaker ones, similar to call type 1. This type of call has a pulse rate of 0.055 - 0.089 pulses per ms and a dominate frequency of 3187 - 3445 Hz, which can modulate by an increase of 87 - 173 Hz. The limits of the fundamental frequency are 3165 - 3346 Hz for the lower limit and 3708 - 3799 Hz for the upper limit (Guayasamin et al. 2015).
Trends and Threats
Based on Maximum Likelihood and Bayesian analysis from combined 12S and 16S genetic sequence data, it is placed in the P. myersi species group (which includes P. leoni, P. trepidotus, P. pyrrhomerus, P. ocreatus, P. thymelensis, P. hectus, P. jubatus, P. celator, P. mutabilis, and P. verecundus). Though it shares the otherwise unique ability to immediately change its skin texture with P. sobetes, genetic evidence shows that the two species are distantly related, with P. sobetes being place in the P. surdus species group (Guayasamin et al. 2015).
Only P. mutabilis and P. sobetes are known to change its skin texture. However, as the two species are not closely related within Pristimantis, it is possible that this trait evolved independently in both species, or that other Pristimantis species too share this trait but have not yet been documented to demonstrate it. Another possibility is that this trait was expressed in the common ancestor of the P. myersi and P. surdus groups, but only retained in P. mutabilis and P. sobetes (Guayasamin et al. 2015).
The specific epithet mutabilis is Latin for the ability to change, in reference to this frog’s ability to change the texture of its skin (Guayasamin et al. 2015).
Guayasamin, J. M., Krynak, T., Krynak, K., Culebras, J., Hutter, C. R. (2015). ''Phenotypic plasticity raises questions for taxonomically important traits: a remarkable new Andean rainfrog (Pristimantis) with the ability to change skin texture.'' Zoological Journal of the Linnean Society, 173, 913-928.
Written by Gordon Lau (gordonhlau AT berkeley.edu), University of California, Berkeley
First submitted 2015-08-25
Edited by Ann T. Chang (2015-10-08)
Species Account Citation: AmphibiaWeb 2015 Pristimantis mutabilis: Mutable Rainfrog <http://amphibiaweb.org/species/8315> University of California, Berkeley, CA, USA. Accessed Dec 11, 2016.
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Citation: AmphibiaWeb. 2016. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 11 Dec 2016.
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