CONVERGENCE IN REFLECTANCE SPECTRA AMONG TREEFROGS

Reflectance spectra between 450-1000 nm were measured on 2 categories of green treefrogs, one of which was thought to reflect near infrared radiation, the other of which was not. Leaf-sitting frog species (Litoria infrafrenata, Agalychnis callidryas, Phyllomedusa sauvagii, Pachymedusa dacnicolor, Rhacophorus malabaricus) had a reflectance spectrum that contrasted significantly from that of the confamilial non near infrared reflecting frog species (Osteopilus septentrionalis, Hyla cinerea, Polypedates leucomystax). In all cases, there was a strong convergence in the reflectance spectra of these distantly related near infrared reflecting frog species. Additionally, for all 5 near infrared reflecting frogs, their reflectance spectra was very similar over the 450-1000 nm waveband to that of leaves, their typical resting sites. Thermoregulation by itself is not the primary biological role of high near infrared reflectance. Rather, this capacity appears to be most likely associated with predator avoidance, functioning to make frogs visually and, perhaps, thermally cryptic to their predators. -from Authors