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Viviparous lizard

Zootoca vivipara
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Lacertidae
Tribe: Lacertini
Genus: Zootoca
Wagler, 1830
Species: Z. vivipara
Binomial name
Zootoca vivipara
(Lichtenstein, 1823)[2]
Synonyms

Lacerta vivipara Lichtenstein, 1823

The viviparous lizard or common lizard, Zootoca vivipara (formerly Lacerta vivipara), is a Eurasian lizard. It lives farther north than any other reptile species, and most populations are viviparous (giving birth to live young), rather than laying eggs as most other lizards do. It is the only species in the monotypic genus Zootoca.[3]

Zootoca vivipara can be seen in a variety of different colors. Female Zootoca vivipara undergo color polymorphism (biology) more commonly than males. A female lizard's display differs in ventral coloration, ranging from pale yellow to bright orange and a mixed coloration. There have been many hypothesis for the genetic cause of this polymorphic coloration. These hypothesis test for coloration due to thermoregulation, predator avoidance, and social cues, specifically sexual reproduction. Through an experiment conducted by Vercken et. al., color polymorphism in viviparous lizard is caused by social cues, rather than the other hypotheses. More specifically, the ventral coloration that is seen in female lizards is associated with patterns of sexual reproduction and sex allocation. [4]


Contents

  • Identification 1
  • Range 2
  • Behaviour 3
  • Color Polymorphism 4
  • Notes 5
  • References 6

Identification

The length of the body is less than 12 cm (5 in) (excluding the tail). The tail is up to twice as long as the body, although it is often partially or wholly lost. The limbs are short, and the head is rather round. Males have more slender bodies than females. The neck and the tail are thick. The collar and other scales seem jagged.

The colour and patterning of this species is variable. The main colour is typically medium brown, but it can be also grey, olive brown or black. Females may have dark stripes on their flanks and down the middle of their backs. Sometimes females also have light-coloured stripes, or dark and light spots along the sides of their backs. Most males and some females have dark spots in their undersides. Males have brightly coloured undersides – typically yellow or orange, but more rarely red. Females have paler, whitish underparts. The throat is white, sometimes blue.

Range

The viviparous lizard is widely distributed throughout Europe and Asia. Its range extends to the north of the Arctic Circle. It ranges from Ireland to Hokkaidō and Sakhalin. It is absent from most of the Mediterranean area, although it occurs in northern Spain, northern Italy, Serbia, Republic of Macedonia and Bulgaria. It is also absent from the area surrounding the Black Sea.

Melanistic specimen are quite typical for the Großer Feldberg/Taunus mountain in Germany
Female

In the southern parts of its distribution range, the species lives at high elevations, occurring as high as 3,000 metres (9,800 ft) above sea level in the Alps. In these areas, the viviparous lizard lives in damp locations, often near water, including meadows, swamps, rice fields, by brooks and in damp forests. In the northern part of the range, the species is also found in lowlands, where it occurs in drier environments, including open woodland, meadows, moorland, heathland, fens, dunes, rocks, roadsides, hedgerows and gardens. It lives mainly on the ground, although it may climb onto rocks, logs and low-growing vegetation.

Behaviour

The viviparous lizard feeds on invertebrates, mostly small insects. It shakes larger prey in its jaws before chewing it and swallowing it whole. In early spring, late autumn, and cool summer days, it basks in the sun to reach its optimum body temperature, which is about 30°C (86°F).

These lizards mate in April or May. Males take females in their jaws before mating – if the female is not interested, she will bite the male fiercely. The offspring develop inside the female for about three months.

The name of the species is derived from its ability to give birth to live young, an adaptation to a cool climate, but some southern populations are oviparous (egg-laying). The three to 10 young (or eggs) are usually produced in July. The blackish young measure about 3 cm (1.2 in), and when first born are surrounded by egg membrane, from which they break free after about a day. Males reach sexual maturity at two years old, females at three years old. Individuals from viviparous and oviparous populations may be hybridized, but with significant embryonic malformation.[5] Viviparous Z. vivipara do develop placentae to facilitate pregnancy but there is no substantial transport of nutrients as seen in some other species of viviparous reptiles (e.g. Pseudemoia entrecasteauxii).

Due to the cool climate, in northern regions, viviparous lizards begin hibernation in September or October, underground or in log piles. Hibernation ends about mid-February. Further south, the species is active throughout the year.

Color Polymorphism

The color polymorphism of Zootoca vivipara has not been thoroughly studied in past years, regardless of the extensive research done on the species itself. More specifically, the color polymorphisms seen in females have been ignored. Although there is much to uncover, few researchers have detailed experiments describing the lizards behavior in regards to its color variations.[6]

Female lizards exhibit three types of body coloration within a population: yellow, orange, and mixture of the two. These traits are inherited maternally and exist throughout the individual’s lifestyle. These traits were not classified through the use of a spectrophotometer, but rather through using human eye. This is because the spectrophotometer classifies these traits as continuous; however, their phenotypes are discrete when observed by the human eye.[7]

The differences in coloration correlates with specific social cues, such as variation in the clutch size of offspring, the ratio of females to males in the clutch, as well as the diversity in reproduction and behavior. The frequency of these colors depend on the individual’s environment in regards to their reproductive success; how frequent a lizard with a certain phenotype is in a population depends on its survival in its environment.[8] However, since coloration remains stable throughout an individual’s lifetime, environmental influence on the emergence of the color itself, perhaps by Phenotypic plasticity, cannot be a great influence for the color polymorphism (biology), or for the color itself appearing.[4] Therefore, color variation must be influenced more by genetics. The heritability (h2) of color in common lizards raised in laboratory approaches 1 (h2= 0.96, Sinervo et. al., 2001).[9] This indicates that nearly all of the variation is due to heritability, or to genetics rather than its environment. [4]

In regards to the diversity and density of the population, the frequency of colored female lizards is dependent on these two factors as well. Two types of populations were studied in correlation with the frequency of polymorphisms. The first population, termed “high quality zone” refers to a population that carries high diversity and high lizard density. The second population, “low quality zone” refers to low diversity and low lizard density. Among these two, color polymorphism was most notable in the low quality zone. This could be due to the fact that the color polymorphisms are more obvious in low quality zones as opposed to high quality zones, where they could be easily hidden.[4] This may also be due to the fact that these lizards thrive in environments where intraspecies competition is low. Increased competition among individuals results in lower survival rates of lizards. Female lizards choose their habitats and disperse based on the frequency of color types already present in the population. This could provide an indication as to why the color polymorphism remains in the population; species confer advantages in environments where intraspecies competition is low, and the coloration of lizards allow for them to disperse according to the density and diversity of the population. [8]

Additionally, female lizard’s reproductive abilities vary in reference to their coloration as well. In a laboratory experiment, it was found that female’s coloration directly responds to how many offspring they produce, and how successful these reproductive abilities are: yellow females produce the fewest offspring, while orange females produce more than yellow, but fewer than mixed females, which produce the most offspring.[4] Moreover, the amount of offspring produced also varies in regards to density of the population; for example, if more yellow females are in the population, clutch size for orange lizards is usually lower. Again, this could be due to competition between individuals; the increase in competition between female lizard’s results in fewer offspring being produced or a decreased success in survival of those offspring.[4]

Notes

  1. ^ A. Agasyan; et al. (2010). "Zootoca vivipara".  
  2. ^ Josef Friedrich Schmidtler1 & Wolfgang Böhme (2011). (Lichtenstein, 1823)"Zootoca vivipara"Synonymy and nomenclatural history of the Common or Viviparous Lizard, by this time: ( 
  3. ^ Harris, D. J. and M. A. Carretero. (2003). Comments on the taxonomic value of (sub)genera within the family Lacertidae (Reptilia). Amphibia-Reptilia 24 119-22.
  4. ^ a b c d e f Vercken, E., Massot, M., Sinervo, B., Clobert, J.2006. Colour Variation and Alternative Reproductive Strategies in Females of the Common Lizard Lacerta vivipara. Journal of Evolutionary Biology 20(1): 221-232
  5. ^ Heulin, B., Arrayago, M. J., and Bea, A. 1989. Expérience d'hybridation entre les souches ovipare et vivipare du lézard Lacerta vivipara. Comp. Rend. Acad. Sci. Series 3 308: 341-346 (cited by the Reptile Database).
  6. ^ Svensson, E.I., Abbott, J., Gosden, T., Coreau, A. 2009. Female polymorphisms, sexual conflict, and limits to speciation processes in animals. Behavioral Evology 23(1) 93-108.
  7. ^ Vercken, E., Sinervo, B., Colbert, J. 2008. Colour Variation in Female Common Lizards: why we should speak of morphs, a reply to Cote et al. Journal of Evolutionary Biology 21(4): 1160-1164.
  8. ^ a b Vercken, E., Sinervo B., Clobert, J. 2012. The Importance of a good neighborhood: dispersal decisions in juvenile common lizards are based on social environment. Behavioral Ecology 23(5) 1059-1067
  9. ^ Sinervo, B., Bleay, C. & Adamopoulou, C. 2001. Social causes of correlational selection and the resolution of a heritable throat color polymorphism in a lizard. Evolution 55: 2040–2052

References

  • E. N. Arnold, J. A. Burton (1978). A Field Guide to Reptiles and Amphibians of Britain and Europe.
  • Jiří Čihař (1994). Amphibians and reptiles. Wingston: Magna. ISBN 1-85422-788-2.
  • ARKive: viviparous lizard.
  • The Reptile Database – Distribution details, authority information.
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