The lizardPsammodromus algirus(Squamata: Lacertidae) is darker at high altitudes

Abstract

Altitudinal gradients offer a good opportunity to study organisms' adaptations to clinal environmental variables. Regarding altitude, the most influential variables on organisms are temperature and ultraviolet (UV) solar radiation, the first decreasing and the second increasing with altitude. Both variables affect ectotherms' biology, as ectotherms depend on environmental temperature for thermoregulation, frequently being heliotherms. Here, we studied dorsal coloration in the lizard Psammodromus algirus (Linnaeus, 1758) along a wide altitudinal gradient (2200 m) in Sierra Nevada (south-east Spain). We hypothesize that the skin will be darker with altitude, i.e. in environments with lower temperatures and higher UV radiation intensity. Results show that individual dorsal colorations became darker at high altitude. We propose two non-mutually exclusive explanations for this result: (1) darker dorsal surface would favour faster warming at high altitudes, where temperature is lower, and (2) darker dorsal surface would protect against UV radiation, stronger at high altitudes. We found significant relationships between both temperature and UV radiation and population dorsal darkness, giving mixed support for the two explanations. Moreover, dorsal hue was positively correlated with substrate hue, suggesting that hue evolved to maximize crypsis. Our study therefore suggests that geographical variation in dorsal coloration in this lizard is adaptive, and darkness coloration might have evolved in response to adverse conditions (low temperature and high UV radiation) at high altitudes.

Thermal dependence of sprint performance in the lizard Psammodromus algirus along a 2200-meter elevational gradient: Cold-habitat lizards do not perform better at low temperatures

“…High-elevation lizards in our study system are larger, and exhibit lower cooling rates, enabling them to retain heat for longer (ZamoraCamacho et al, 2014b). Furthermore, they are darker (Reguera et al, 2014), this presumably helping them to warm up faster (Clusella-Trullas et al, 2007). Moreover, high-elevation P. algirus probably bask for longer periods, as reported for other alpine lizards (Carrascal et al, 1992;Gvoždík, 2002;Hertz, 1992).…”

“…For accurate detection of geographical trends, we grouped those sampling plots into three elevation belts: low elevations (plots at 300 and 700 m asl), mid elevations (plots at 1200 and 1700 m asl), and high elevations (plots at 2200 and 2500 m asl). Grouping in elevation belts was justified on the basis of similarities in population traits within belts, such as phenology, demography, morphology, and even genetic structure (Reguera et al, 2014;Zamora-Camacho et al, 2013, 2014aunpublished data). Since habitat landscape can affect the flight strategy of this species (Iraeta et al, 2010;Martín and López, 1995), we chose locations as similar as possible regarding vegetation structure (see Appendix A in Zamora-Camacho et al, 2013).…”

“…In fact, lizards from this system selected similar body temperatures in a laboratory thermal gradient, regardless of their elevational provenance (Zamora-Camacho et al, submitted). Therefore, lizards in the highest elevations seem to have adaptations such as darker dorsal color (Reguera et al, 2014) and larger body size (Zamora-Camacho et al, 2014b) that may allow them to cope with low environment temperature. Consequently, given that lizards from different elevations show similar body temperature, it is not surprising that they also show similar maximal sprint speed in experiments under controlled body temperature (32°C; Zamora-Camacho et al, 2014a).…”

Effect of body mass and melanism on heat balance inLiolaemuslizards of thegoetschiclade

“…It has been considered an accelerator for heat gain (e.g. Kettlewell, 1973;Kingsolver and Wiernasz, 1991;Clusella-Trullas et al, 2007;Reguera et al, 2014); however, it also is associated with UV radiation protection (Gunn, 1998;Callaghan et al, 2004;Calbó et al, 2005;Reguera et al, 2014), crypsis (Kettlewell, 1973;Endler, 1984;Reguera et al, 2014) and intra-specific communication or sexual selection (Wiernasz, 1989;Fedorka et al, 2013). Additionally, the advantages of melanism may be associated with local conditions (local adaptation; Castella et al, 2013), as a result of phenotypic plasticity (Alho et al, 2010) or the interaction between predator avoidance and thermoregulation (Lindstedt et al, 2009).…”

Does tail autotomy affect thermoregulation in an accurately thermoregulating lizard? Lessons from a 2200‐m elevational gradient

“…and high elevations (populations at 2200 and 2500 m a.s.l.). Population similarities in activity patterns, demography, morphology and even genetic structure support this grouping (Zamora‐Camacho et al ., ; Reguera, Zamora‐Camacho & Moreno‐Rueda, ; Reguera et al ., unpublished data).…”