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.