4 Discussion
Morphological characteristics of reptiles are in direct correlation with their ecology, and may reflect their phylogenetic and evolution information, their trophic potential, their ability to survive in specific habitats, and they can thus be used to predict their lifestyle (Wootton, 1994; Gibran, 2007; Allam et al., 2019). Overall, tracing their morphological, behavioral, and physiological adaptations in relation to ecological factors requires an understanding of historical and phylogenetic relationships among taxa. This information is also necessary to determine morphological and ecological convergence and divergence within a taxon (Wainwright and Lauder, 1992; Westneat, 1995). Reptile scale microornamentation as a morphological character has been studied in various contexts of phylogeny and ecological adaptations (Picado, 1931; Peterson and Bezy, 1985; Renous et al., 1985; Stille, 1987; Irish et al., 1988; Chiasson et al., 1989; Chiasson and Lowe, 1989; Price, 1990; Harvey, 1993; Harvey and Gutberlet Jr, 1995; Maderson et al., 1998; Arnold, 2002; Gower, 2003) and used as an argument to support phylogenetic relationships of species (Picado, 1931; Price, 1983; Stille, 1987; Chiasson et al., 1989; Chiasson and Lowe, 1989; Gower, 2003). However, some authors asserted that microornamentation depends on selective pressures, especially in snakes. There are many contacts between the body surface and the environment; however, some studies indicated no relationship between microornamentation and environment (Price, 1982; Peterson, 1984; Peterson and Bezy, 1985; Berthé et al., 2009). P. urarachnoides is well separated morphologically from its congeners, P. fieldi and P. persicus , (Fathinia et al., 2014), while is the sister taxon toP. persicus the P. fieldi phylogenetically, with a basal position for P. fieldi (Fathinia et al., 2018). Although the most common recent ancestor (MRCA) for P. persicus and P. urarachnoides dates back to ~ 8 mya (Fathinia et al., 2018), P. persicus is morphologically more similar to P. fieldi (MRCA; ~12 mya) than to P. urarachnoides . Some morphological characteristics that can be regarded as autapomorphies for P. urarachnoides are the unique caudal structure and rugosity of scales in comparison to its congeners, which deeply separate it from its two congeners (Bostanchi et al., 2006; Fathinia and Rastegar-Pouyani, 2010). Scale microornamentation revealed that the microstructure of scales in P. fieldi and P. persicus are more similar to each other than to P. urarachnoides , coincides with morphological characteristics, but contrary to molecular relationships within this genus. The genusEristicophis is the closest living relative toPseudocerastes , with the MRCA dates back to ~16.5 Mya ( Fathinia et al., 2018). Lattice-like scale microstructure inE. macmahonii is more or less similar to that in P. fieldi. The genera Cerastes and Echis are closer relatives in comparison to other viperin genera used in this study (Pyron et al., 2013). Similarities in the scale microornamentation between E. carinatus and C. gasperettii (i.e., the raised prominences) are obvious. In both E. rafsanjanicus and L. maynardi scales microstructure was smooth.
According to the phylogenetic and ecologic information mentioned above, there are many scale microstructure differences between P. urarachnoides and other congeners that inhabit almost the same habitat, while there are microstructure similarities between P. fieldi andE. macmahonii or E. carinatus and C. gasperettiithat inhabit different habitats. Therefore, based on the presence of similar microstructures found in different taxa living in different habitats and various microstructures that found in different species occupying similar ecological niches, and given the phylogenetic relationships, one can interpret that with all probability these microstructures do not affect by habitat, so mostly inherited from the common ancestors. As some researchers have pointed out, variation in microornamentations in different species does not indicate any adaptation to different environments (Price, 1982; Peterson, 1984; Peterson and Bezy, 1985). Overall, the difference in the scales microornamentation between P. urarachnoides and its congeners can be explained with regard to other factors such as the nocturnality or diurnality, dietary regime, and so on.
Ultraviolet light has benefit impacts on ecological and physiological aspects of reptiles well being. It plays a role in social communication, calcium metabolism through an apparent vitamin D3 precursor, photoperiod regulations that influences on reproduction and behavior and many known and unknown advatages (MacLaughlin, et al, 1982; ; Holick, et al, 1995; Ferguson, et al, 2003; Modarressie et al., 2013). Despite the advantage effects, UV light also has disadvantage effects on the reptiles. For instance, UV light reflection from reptiles body surface help avian predators to detect them (Bennett and Cuthill, 1994) or it can cause degradation of vitamin A in the skin (Tang, et al, 1994). Accordingly, reptiles have different adaptations to ultraviolet light due to their ecological and physiological conditions. In examining the relationship between scale reflection and ecology, various reflections were seen in different species and different parts of their body. In the UV light range, P. urarachnoides dorsal scales reflected low, while the caudal structure (the terminal knob) showed strong UV reflection. One of the benefits of this feature can be investigated in enemy-victim behavior. Many bird species can perceive near-UV part of the light spectrum (the wavelength 320–400 nm) (Rajchard, 2009). The ecological significance of UV perception was investigated mostly in intra- and inter-sexual signaling in common species communication and foraging behavior (Rajchard, 2009). Given that the caudal structure (the appendages and terminal knob) in P. urarachnoides reflects UV light, while the rest of the body highly absorbs the UV light, might have a bifunctional role in both seducing and absorbing insectivorous passerine birds and camouflage against these birds. A complete scene of predation on birds by the Iranian spider-tailed viper has reported previously by Fathinia et al. (2015), in which the warbler incautiously attacks the caudal structure after the first unfruitful attack, as if the warbler has not noticed the presence of the head and body of Spider-tailed viper, only aimed at the tail of the viper. The emergence of this feature between P. urarachnoides and the birds can be considered as a model of prey-predator coevolution. The term ”coevolution” is defined in the simplest form; two species evolve in response to each other (Futuyma, 1998). In this case, P. urarachnoides have evolved a spider-like caudal structure reflecting UV light, as an extraordinary evolutionary innovation, for absorbing passerine insectivorous birds as prey.