Ctenophorus pictus: Difference between revisions
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==Colour polymorphism== |
==Colour polymorphism== |
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| ⚫ | Coloration in male painted dragon populations, ''Ctenophorus pictus'', is extremely variable, ranging from reddish-brown to orange to yellowish-brown, with orange being the least common. In studies of color polymorphism, individual lizards have been categorized by their predominant color into three discrete groups, red, orange and yellow.<ref name="ReferenceA">{{cite journal|last1=McLean|first1=Claire A.|last2=Stuart-Fox|first2=Devi|last3=Moussalli|first3=Adnan|title=Environment, but not genetic divergence, influences geographic variation in colour morph frequencies in a lizard|journal=BMC Evolutionary Biology|date=8 August 2015|volume=15|issue=1|doi=10.1186/s12862-015-0442-x}}</ref>The differences in male coloration have also been found to be related to lizard behavior, in both the males and females. |
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Colour polymorphism in ''Ctenophorus pictus'' has not been widely studied, but some findings have been made regarding these differences in appearance, particularly in males, as a male lizard's behaviour seems to be influenced by its colour. |
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The variable appearance of the males has been correlated to higher sexual selection as it has been found that, between yellow and red coloured male lizards, female lizards prefer red coloured ones.<ref>{{cite journal|last1=Healey|first1=Mo|last2=Uller|first2=Tobias|last3=Olsson|first3=Mats|title=Seeing red: morph-specific contest success and survival rates in a colour-polymorphic agamid lizard|journal=Animal Behaviour|date=August 2007|volume=74|issue=2|pages=337–341|doi=10.1016/j.anbehav.2006.09.017}}</ref> The females chose males that are naturally red, based on genes, as well as lizards that just appeared red due to the environment, equally. The red coloration may indicate indirect benefits to the females, showing that the male has good genes. |
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| ⚫ | Coloration in male painted dragon populations is extremely variable, ranging from reddish-brown to orange to yellowish-brown, with orange being the least common. In studies of |
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In addition to preference of the red variants by females, red males also have higher testosterone levels than their yellow male counterparts. The red male lizards also experience a more rapid increase in testosterone levels.<ref>{{cite journal|last1=Olsson|first1=Mats|last2=Healey|first2=Mo|last3=Astheimer|first3=Lee|title=Afternoon T: Testosterone level is higher in red than yellow male polychromatic lizards|journal=Physiology & Behavior|date=August 2007|volume=91|issue=5|pages=531–534|doi=10.1016/j.physbeh.2007.04.025}}</ref> In mating situations, red lizards may out-compete yellow lizards, because they will be ready to mate faster. Testosterone is also linked to aggression; increased aggression seen from a rapid increase in testosterone levels in red lizards also gives them a fighting advantage over predators and other lizards. |
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Red males show more aggressive strategies in out-competing the yellow males and getting more mating opportunities. The red males defend their territory more fiercely and begin this behavior earlier in the year,<ref>{{cite journal|last1=Olsson|first1=Mats|last2=Schwartz|first2=Tonia|last3=Uller|first3=Tobias|last4=Healey|first4=Mo|title=Effects of sperm storage and male colour on probability of paternity in a polychromatic lizard|journal=Animal Behaviour|date=February 2009|volume=77|issue=2|pages=419–424|doi=10.1016/j.anbehav.2008.10.017}}</ref> gaining a behavioral dominance over yellow males. |
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| ⚫ | This increased aggression, in addition to early defending of territory, takes a metabolic toll on the red lizards. This energy cost decreases the fitness of the red males overall. Thus, even though females may show a higher preference for red males, yellow males have high survival rates as well, since they do not use as much energy in territory defense. This may be one of the explanations for why both color morphs are maintained in the population. |
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While yellow males have higher sperm counts, red males have other behavioural traits that lead to high reproductive success.<ref>{{cite journal|last1=OLSSON|first1=MATS|last2=HEALEY|first2=MO|last3=WAPSTRA|first3=ERIK|last4=SCHWARTZ|first4=TONIA|last5=LEBAS|first5=NATASHA|last6=ULLER|first6=TOBIAS|title=Mating system variation and morph fluctuations in a polymorphic lizard|journal=Molecular Ecology|date=December 2007|volume=16|issue=24|pages=5307–5315|doi=10.1111/j.1365-294X.2007.03578.x}}</ref> They show more aggressive strategies in out-competing the yellow males and getting more mating opportunities. The red males defend their territory more fiercely and begin this behaviour earlier in the year,<ref name="ReferenceB"/> gaining a behavioural dominance over yellow males. |
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In addition to preference of the red variants by females, red males also have higher testosterone levels than their yellow male counterparts. The red male lizards also experience a more rapid increase in testosterone levels.<ref>{{cite journal|last1=Olsson|first1=Mats|last2=Healey|first2=Mo|last3=Astheimer|first3=Lee|title=Afternoon T: Testosterone level is higher in red than yellow male polychromatic lizards|journal=Physiology & Behavior|date=August 2007|volume=91|issue=5|pages=531–534|doi=10.1016/j.physbeh.2007.04.025}}</ref> In mating situations, red lizards may out-compete yellow lizards, because they will be ready to mate faster. Testosterone is also linked to aggression; increased aggression seen from a rapid increase in testosterone levels in red lizards also gives them a fighting advantage over predators and other lizards. |
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Yellow males have been found to have higher sperm levels than red males.<ref name="ReferenceB">{{cite journal|last1=Olsson|first1=Mats|last2=Schwartz|first2=Tonia|last3=Uller|first3=Tobias|last4=Healey|first4=Mo|title=Effects of sperm storage and male colour on probability of paternity in a polychromatic lizard|journal=Animal Behaviour|date=February 2009|volume=77|issue=2|pages=419–424|doi=10.1016/j.anbehav.2008.10.017}}</ref> The size of the yellow males’ testes is also three times the size of the red males, and they copulate for shorter periods of time. This is one way that the yellow morph displays a selection advantage, and how this variant is maintained in the populations. |
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| ⚫ | This increased aggression, in addition to early defending of territory, takes a metabolic toll on the red lizards. This energy cost decreases the fitness of the red males overall. Thus, even though females may show a higher preference for red males, |
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Although it seems that red lizards are the superior variant, all the polymorphs still exist in nature. The reason for this is that variation in polymorphic lizards is maintained in different environments. The variation is often found between, rather than within, populations. |
Although it seems that red lizards are the superior variant in terms of sexual selection, all the polymorphs still exist in nature. The reason for this is that variation in polymorphic lizards is maintained in different environments. The variation is often found between, rather than within, populations. Some environments are better suited for the survival of yellow variants; in others, red variants have higher fitness. Females have largely been shown to prefer red males. However, yellow males have high survival rates since they use energy for sustenance and survival, rather than impressing females. This shows that natural selection has a large role in maintaining variation, even more so than gene flow.<ref name="ReferenceA"/> |
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==References== |
==References== |
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Revision as of 15:48, 9 November 2015
| Ctenophorus pictus | |
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| Ctenophorus pictus, painted dragon | |
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| Species: | C. pictus
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| Binomial name | |
| Ctenophorus pictus (W. Peters, 1866)
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Ctenophorus pictus, commonly known as the painted dragon,[2] is a species of lizard from the Agamidae family. Ctenophorus pictus is endemic to the drier areas of southern and central Australia.
Description
dorsal view
The painted dragon is a medium-sized terrestrial lizard with a short, deep head and uniform body scales. The appearance of this species is extremely variable as it can appear in a number of different colour combinations.[3] Adult males can be brown, yellowish-brown, orange to reddish-brown with dark-edged pale bars, blotches or spots overlaying a dark vertebral stripe.[3] The flanks are spotted, variegated (irregular patches/streaks), or reticulated (net-like pattern) with dark brown and dotted with scattered, pale, dark-edged spots which will sometimes be aligned perpendicular to the vertebral stripe.[4] The limbs are variegated and the pattern on the tail is often obscure but broad dark bands at the base.[4] Breeding males will exhibit a bright blue flush over the lower lips, throat and limbs and a bright yellow to orange flush over the anterior chest and shoulders.[3] Adult females and juveniles are duller in colour, lacking the bright blue and yellow pigment[3] with females being commonly found in a rusty brown colour.[2]
The scales, though varying slightly in size in different parts, are relatively uniform across the body[2] and are smooth to the touch.[4] A low crest on the back of the neck is often present which males will raise when alarmed[5] and usually a distinct vertebral series of slightly enlarged scales can be found along the back.[4] The ears are exposed on the side of its head and it has rather large and conspicuous eardrums.[4]
Adults will grow to a full length of around 18–25 cm (7.1–9.8 in), with a snout-to-vent length of about 7.5 cm (3.0 in).[3][5] The tail of this species usually accounts for about 65% of its total body length.[4]
Distribution and habitat
Painted dragons are found throughout the drier parts of south-eastern Western Australia, across South Australia to north-western Victoria and central-western New South Wales.[4] They prefer semi-arid to arid regions, favouring shrublands and hummock grasslands on sandy and saline soils.[3]
Ecology
Like most agamids, painted dragons are swift-moving reptiles, capable of impressive sprints over short distances.[6] This diurnal (day-active) lizard, like the majority reptiles, is an ectotherm meaning that it has to rely on its environment to regulate body temperature and as a result will spend considerable time basking to absorb heat.[7] Known to be especially fond of low vegetation and ground debris such as fallen logs and branches,[4] it occupies short burrows often concealed at the base of shrubs such as saltbush.[3][5] Unlike the majority of other agamids which like to perch in elevated places,[6] this species prefers to rest on low branches,[3] from which it will forage over the surrounding open areas and ground litter.[3][4][5] When disturbed or alarmed it will quickly retreat to the safety of the nearby burrow.[5]
Painted dragons possess many of the traits common to the Agamidae family. They are very alert lizards with an upright stance and acute vision which they will use to search for prey and keep an eye out for mates, rivals, and predators.[6] Most of their communication is visually oriented with stylised head bops and dips, arm waving, and tail lashing playing a big part.[6] When looking for food, agamids will seize their prey with the use of a short, thick tongue rather than their jaws.[6]
Diet
Employing a sit-and-wait hunting technique, painted dragons will use their keen vision to detect most of their prey by the telltale movement they make.[6] Accordingly, their diets consist largely of surface-active, mobile prey resulting in them consuming a range of arthropods. A strange feature of the Agamidae family is that ants, which are often avoided by other lizards, feature prominently in the diets of many of its species.[6] While it is believed that this is more of a reflection on availability than preference, it still remains to be explained why they take ants at all when so many other lizards actively avoid them due to the formic acid they contain.[6] It is presumed that they have developed some sort of mechanism to deal with the ingestion of this chemical.[6]
While this species is known to be predominately insectivorous,[5] specimens kept in captivity have been observed supplementing their diet with considerable amounts of plant matter.[7]
Colour polymorphism
Coloration in male painted dragon populations, Ctenophorus pictus, is extremely variable, ranging from reddish-brown to orange to yellowish-brown, with orange being the least common. In studies of color polymorphism, individual lizards have been categorized by their predominant color into three discrete groups, red, orange and yellow.[8]The differences in male coloration have also been found to be related to lizard behavior, in both the males and females.
The variable appearance of the males has been correlated to higher sexual selection as it has been found that, between yellow and red coloured male lizards, female lizards prefer red coloured ones.[9] The females chose males that are naturally red, based on genes, as well as lizards that just appeared red due to the environment, equally. The red coloration may indicate indirect benefits to the females, showing that the male has good genes.
In addition to preference of the red variants by females, red males also have higher testosterone levels than their yellow male counterparts. The red male lizards also experience a more rapid increase in testosterone levels.[10] In mating situations, red lizards may out-compete yellow lizards, because they will be ready to mate faster. Testosterone is also linked to aggression; increased aggression seen from a rapid increase in testosterone levels in red lizards also gives them a fighting advantage over predators and other lizards.
Red males show more aggressive strategies in out-competing the yellow males and getting more mating opportunities. The red males defend their territory more fiercely and begin this behavior earlier in the year,[11] gaining a behavioral dominance over yellow males.
This increased aggression, in addition to early defending of territory, takes a metabolic toll on the red lizards. This energy cost decreases the fitness of the red males overall. Thus, even though females may show a higher preference for red males, yellow males have high survival rates as well, since they do not use as much energy in territory defense. This may be one of the explanations for why both color morphs are maintained in the population.
Yellow males have been found to have higher sperm levels than red males.[12] The size of the yellow males’ testes is also three times the size of the red males, and they copulate for shorter periods of time. This is one way that the yellow morph displays a selection advantage, and how this variant is maintained in the populations.
Although it seems that red lizards are the superior variant in terms of sexual selection, all the polymorphs still exist in nature. The reason for this is that variation in polymorphic lizards is maintained in different environments. The variation is often found between, rather than within, populations. Some environments are better suited for the survival of yellow variants; in others, red variants have higher fitness. Females have largely been shown to prefer red males. However, yellow males have high survival rates since they use energy for sustenance and survival, rather than impressing females. This shows that natural selection has a large role in maintaining variation, even more so than gene flow.[8]
References
- ^ The Reptile Database. www.reptile-database.org.
- ^ a b c Waite ER (Editor). (1929). The Reptiles and Amphibians of South Australia. Adelaide: Government Printer. 270 pp.
- ^ a b c d e f g h i Wilson S, Swan G. (2013). A Complete Guide to Reptiles of Australia (Fourth Edition). London: New Holland Publishers. 592 pp. ISBN 978-1921517280.
- ^ a b c d e f g h i Cogger HG. (2014). Reptiles & Amphibians of Australia. Seventh Edition. Collingwood: CSIRO Publishing. 1,036 pp. ISBN 978-0643100350 (paperback).
- ^ a b c d e f Hoser RT. (1989). Australian Reptiles and Frogs. Sydney: Pierson & Co.
- ^ a b c d e f g h i Wilson SK. (2012). Australian Lizards: A Natural History. Collingwood: CSIRO Publishing. 208 pp. ISBN 978-0643106406.
- ^ a b Mayhew WW (1963). "Observations on Captive Amphibolurus pictus an Australian Agamid Lizard". Herpetologica. 19 (2): 81–88. JSTOR 3890542.
- ^ a b McLean, Claire A.; Stuart-Fox, Devi; Moussalli, Adnan (8 August 2015). "Environment, but not genetic divergence, influences geographic variation in colour morph frequencies in a lizard". BMC Evolutionary Biology. 15 (1). doi:10.1186/s12862-015-0442-x.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Healey, Mo; Uller, Tobias; Olsson, Mats (August 2007). "Seeing red: morph-specific contest success and survival rates in a colour-polymorphic agamid lizard". Animal Behaviour. 74 (2): 337–341. doi:10.1016/j.anbehav.2006.09.017.
- ^ Olsson, Mats; Healey, Mo; Astheimer, Lee (August 2007). "Afternoon T: Testosterone level is higher in red than yellow male polychromatic lizards". Physiology & Behavior. 91 (5): 531–534. doi:10.1016/j.physbeh.2007.04.025.
- ^ Olsson, Mats; Schwartz, Tonia; Uller, Tobias; Healey, Mo (February 2009). "Effects of sperm storage and male colour on probability of paternity in a polychromatic lizard". Animal Behaviour. 77 (2): 419–424. doi:10.1016/j.anbehav.2008.10.017.
- ^ Olsson, Mats; Schwartz, Tonia; Uller, Tobias; Healey, Mo (February 2009). "Effects of sperm storage and male colour on probability of paternity in a polychromatic lizard". Animal Behaviour. 77 (2): 419–424. doi:10.1016/j.anbehav.2008.10.017.
Further reading
- Boulenger GA. (1885). Catalogue of the Lizards in the British Museum (Natural History). Second Edition. Volume I. ... Agamidæ. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xii + 436 pp. + Plates I-XXXII. (Amphibolurus pictus, pp. 385–386).
- Peters W. (1866). "Mittheilung über neue Amphibien (Amphibolurus, Lygosoma, Cyclodus, Masticophis, Crotaphopeltis) und Fische (Diagramma, Hapalogenys) des Kgl. Zoologischens Museums". Monatsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin 1866: 86–96. (Amphibolurus pictus, new species, pp. 88–89). (in German).