Common Lizard
Zootoca vivipara
Description 2
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 color and patterning of this species is variable. The main color 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-colored 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 colored undersides – typically yellow or orange, but more rarely red. Females have paler, whitish underparts. The throat is white, sometimes blue.
The color polymorphism of female Zootoca vivipara has not been thoroughly studied in past years, regardless of the extensive research done on the species itself. Female lizards exhibit three types of body coloration within a population: yellow, orange, and mixture of the two. These discrete traits are inherited maternally and exist throughout the individual’s lifetime. The organism's color morphs are determined by their genotype as well as their environment.
The frequency of multiple morphs occurring in a population varies with the level of population density and frequency-dependent environments. These factors cause the lizards to vary in terms of their fitness (clutch size, sex ratio, hatching success). In lower density populations, color polymorphism is more prevalent. This is because viviparous lizards thrive in environments where intraspecific competition is low. Increased competition among individuals results in lower survival rates of lizards. Additionally, female lizards disperse through habitats based on the frequency of color types that are already present in the population. Their reproductive abilities vary according to this frequency-dependent environment. The number of offspring that they produce correlates with the color morph: yellow females produce the fewest offspring, while orange females produce more than yellow, but fewer than mixed females, which produce the most offspring. The amount of offspring produced varies in regards to color frequencies in the population; for example, if yellow females have higher density within the population, the clutch size for orange lizards is usually lower.
Orange females are more sensitive to intraspecific and color-specific competition. They have smaller clutch sizes when the density of the population is high, or when the number of yellow females in the population is high. This could be due to their need to conserve energy for survival and reproductive events. Their color morph remains in the population due to the trade-off between the size of offspring and the clutch size. Offspring born in smaller clutches are often larger and thus have a higher survival likelihood. Natural selection will favor individuals with larger size because of their advantage in physical competition with others. Yellow females have larger clutch sizes early in their life, but their hatch success decreases as the female ages. Their reproductive viability decreases, resulting in fewer offspring throughout their lifetime. Yellow morphs remain in the population due to their large clutch size, which causes an increased frequency of those females. Selection favors the yellow morph because of the ability to produce large clutch sizes, which increases the female's fitness. In mixed-colored females, reproductive success is less sensitive to competition and frequency-dependent environments. Since these lizards show a mixture of yellow and orange coloration, they adopt benefits from both of the morphs. As a result, they can maintain high reproductive success and hatching success with large clutch sizes. Their color morph remains in the population due to its high fitness, which selection will favor.
All three colors have evolutionary advantages in different ways. While yellow females have higher fitness due to their large clutch sizes, orange females enjoy high fitness due to their large body size and increase competitive advantages. Mixed females exhibit both of these advantages.
Fontes e Créditos
- (c) Aleksandar, alguns direitos reservados (CC BY-SA), uploaded by Aleksandar
- Adaptado por Aleksandar de uma obra de (c) Wikipedia, alguns direitos reservados (CC BY-SA), http://en.wikipedia.org/wiki/Viviparous_lizard
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