Now you see me, now you don’t: iridescence increases the efficacy of lizard chromatic signals
- 495 Downloads
The selective forces imposed by primary receivers and unintended eavesdroppers of animal signals often act in opposite directions, constraining the development of conspicuous coloration. Because iridescent colours change their chromatic properties with viewer angle, iridescence offers a potential mechanism to relax this trade-off when the relevant observers involved in the evolution of signal design adopt different viewer geometries. We used reflectance spectrophotometry and visual modelling to test if the striking blue head coloration of males of the lizard Lacerta schreibeiri (1) is iridescent and (2) is more conspicuous when viewed from the perspective of conspecifics than from that of the main predators of adult L. schreibeiri (raptors). We demonstrate that the blue heads of L. schreiberi show angle-dependent changes in their chromatic properties. This variation allows the blue heads to be relatively conspicuous to conspecific viewers located in the same horizontal plane as the sender, while simultaneously being relatively cryptic to birds that see it from above. This study is the first to suggest the use of angle-dependent chromatic signals in lizards, and provides the first evidence of the adaptive function of iridescent coloration based on its detectability to different observers.
KeywordsColoration Communication Lizard Signal efficacy Viewer geometry Visual modelling
We are especially grateful to J. Heredero for the design and construction of the goniometer. We thank M. C. Stoddard for helping with TetraColorSpace, and L. J. Fleishman for generously sharing with us visual sensitivity data for Platysaurus broadleyi. This work was funded by a Portuguese FCT postdoctoral fellowship (SFRH/BPD/94582/2013) and a project from the Ministerio de Ciencia e Innovación (CGL2011-23751).
The study was performed according to guidelines provided by the Association for the Study of Animal Behaviour (ASAB) and the Animal Behavior Society (ABS). The experiments complied with current EU and Spanish laws and permits were generously provided by the Sierra Norte de Guadalajara Natural Park (Junta de Castilla-la Mancha).
- Andersson S, Prager M (2006) Quantification of coloration. In: Hill GE, McGraw KJ (eds) Bird Coloration, Vol. 1. Mechanisms and Measurements. Harvard University Press, Cambridge, pp 41–89Google Scholar
- Bradbury JW, Vehrencamp SL (2011) Principles of animal communication, 2nd edn. Sinauer Assoc Press, SunderlandGoogle Scholar
- Pérez i de Lanuza G (2012) Visió en color i coloracions dels lacèrtids. PhD thesis, University of València, ValènciaGoogle Scholar
- Pérez i de Lanuza G, Font E (2011) Lizard blues: blue body colouration and ultraviolet polychromatism in lacertids. Rev Esp Herp 24:67–84Google Scholar
- Pérez-Mellado V (1998) Lacerta schreiberi Bedriaga, 1878. In: Salvador A (coord) Reptiles. Fauna Ibérica. Vol. 10. Museo Nacional de Ciencias Naturales, Madrid, pp 218–227Google Scholar
- Prum RO (2006) Anatomy, physics, and evolution of avian structural colors. In: Hill GE, McGraw KJ (eds) Bird coloration, vol 1, Mechanisms and measurements. Harvard University Press, Cambridge, pp 295–355Google Scholar
- Saranathan V, Forster JD, Noh H, Liew S-F, Mochrie SGJ, Cao H, Dufresne ER, Prum RO (2012) Structure and optical function of amorphous photonic angle X-ray scattering (SAXS) analysis of 230 bird species nanostructures from avian feather barbs: a comparative small. J R Soc Interface 9:2563–2580. doi: 10.1098/rsif.2012.0191 PubMedCentralPubMedCrossRefGoogle Scholar
- Stuart-Fox D, Godinho R, de Bellocq JG, Irwin NR, Brito JC, Moussalli A, Široky P, Hugall AF, Baird SJE (2009) Variation in phenotype, parasite load and male competitive ability across a cryptic hybrid zone. PLoS ONE 4:e5677. doi: 10.1371/journal.pone.0005677 PubMedCentralPubMedCrossRefGoogle Scholar