Divergence of visual motion detection in diurnal geckos that inhabit bright and dark habitats

Abstract

Summary1. Recent studies of the sensory drive hypothesis suggest that communicative signals evolve readily whereas change in sensory perception is more constrained by the demands of the physical environment. 2. Here, we find that diurnal Sphaerodactylus macrolepis geckos collected from dark, forested habitats were best able to detect motion in very dim light (< 10 lux), whereas geckos collected in brightly-lit coastal areas exhibited optimal motion detection at a much brighter light range 200-300 lux. 3. Motion detection by geckos from both habitat types declined as light intensity increased above 300 lux. These differences were observed after the lizards had been living in a common laboratory environment for 1 full year and are hence unlikely to be due to acclimation effects. 4. Light conditions for optimal visual performance match the light conditions of the natural habitats in which the lizards are found. Our results support the suggestion that visual performance may evolve quickly and that the sensory drive process may be best described as repeated coevolution between signals and receiver sensory systems. 5. Thus, for animals that inhabit wide ranges of visual habitats, the sensory drive process may potentially act differently on separate visual response properties, resulting in diverse levels of variation and divergence in visual performance and communication systems.

Sex-specific visual performance: female lizards outperform males in motion detection

“…We measured the latency of the VGR (methods similar to Nava et al 2009) in 18 male and six female S. graciosus lizards (from pine scrub habitats in the San Gabriel Mountains of southern California, USA) to a motion stimulus under two light intensities (bright: 500 lx and dim: 10 lx). We randomly tested all lizards first under the bright lighting and then under the dim lighting.…”

“…Light intensity can affect VGR performance in diurnal lizards (Nava et al 2009); thus, for comparison, we tested lizards under bright and dim light. Based on previous work (Martins et al 2005), we tested the hypothesis that female S. graciosus lizards should detect motion faster than males.…”

The biomechanical basis of evolutionary change in a territorial display

“…Mechanistic perspectives are certainly not lacking in communication research – quite the contrary (e.g. see Nava, Conway & Martins ; Henningsen & Irschick ; and reviews by Lailvaux & Irschick and Irschick et al . ) – but where this approach has been adopted, it generally focuses on model organisms and with limited consideration (if any) of how biomechanical constraints affect signal performance and differentiation among taxa.…”

“…With the emergence of the ‘sensory drive’ concept in animal communication ( sensu Endler ), many researchers turned their attention to the sensory physiology of receivers and its role in signal divergence (e.g. Ryan ; Wilczynski, Rand & Ryan ; Nava, Conway & Martins ; Tobias et al . ; Ord ).…”

Light level impacts locomotor biomechanics in a secondarily diurnal gecko,Rhoptropus afer

“…Daytime ambient light levels can vary dramatically among habitats via a number of factors, such as canopy cover in a forest (Nava et al, 2009b;Pringle et al, 2003), cloud cover and fog level. The collection of suspended water droplets near the Earth's surface, resulting in fog, reduces horizontal visibility by reducing brightness contrast between an object and its background, and by scattering and absorbing light as a result of the presence of the droplets (Cronin et al, 2014;Gultepe et al, 2007;Houghton, 1931).…”