Urosaurus ornatus

Urosaurus ornatus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Squamata
Suborder: Lacertilia
Infraorder: Iguania
Family: Phrynosomatidae
Genus: Urosaurus
Species: U. ornatus
Binomial name
Urosaurus ornatus
(Baird & Girard, 1852)
Synonyms[2]
  • Uta ornata
    Baird & Girard, 1852
  • Urosaurus ornatus
    — Mittleman, 1942

Urosaurus ornatus, commonly known as the ornate tree lizard, is a species of lizard native to the southwestern United States and northwestern Mexico. The species, which formerly was commonly called simply the "tree lizard", has been used to study physiological changes during the fight-or-flight response as related to stress and aggressive competition.[3][4] Also, its life history and costs of reproduction have been documented in field populations in New Mexico and Arizona.[5][6] Finally, it has been fairly well studied because it has interesting variation in throat color in males (within a population) that can correlate with different reproductive strategies,[7][8]

Diet

The ornate tree lizard feeds on mostly insects and their larvae.

Reproduction

A group consisting of one male and one or more females typically inhabit an area containing one or more large trees, shrubs, or boulders. The male copulates with each female and the female retain eggs about two weeks after mating. In many parts of its range, females may lay more than one clutch of eggs a year.

Territoriality is an important part of reproduction for many males in this species. Males often defend territories by aggressively excluding other males. This aggression can, in part, be enhanced with higher levels of the steroid hormones testosterone and progesterone.[9] Females have home ranges but do not defend territories. When the number of females on a male's territory is experimentally reduced by removing the females, the male is more likely to abandon his territory.[10]

Females also can vary in throat coloration, although this is not as well-studied. When gravid with eggs, females tend to be orange or red.[11] Recent experiments also suggest females have association, and perhaps mating preferences for different male types, and that this female preference varies with the throat color of the female herself, and with the colors of the two males that she was presented.[12]

Appearance and throat color variation

As adults, all males have paired turquoise patches of skin on the abdomen; females lack this abdominal coloration.[13] Male ornate tree lizards are found in a variety of colors.[14][7] While not all populations contain more than one or two colors, 9 color types have been documented within U. ornatus. A population documented in Verde River, Arizona, has two types of coloration patterns among male tree lizards that account for 45% of all males. The first is characterized by a blue spot in the center of a larger orange patch on the throat fan ("dewlap"). The second is has a solid orange throat fan ("dewlap"). The orange-blue males are more aggressive and defend territories that can include up to four females.[15] The orange males have longer, leaner body types and are much less aggressive. Orange males can be nomadic during dry years, and during rainy years tend to occupy small territories.[16]

Some, such as Stanford professor and biologist Joan Roughgarden, have suggested multiple male genders in this species. Among differently colored male tree lizards, there are different hormonal profiles. On the day a male tree lizard hatches, researchers think that high blood levels of progesterone and then later, as a juvenile, higher testosterone levels will cause him to develop into an orange-blue type; low progesterone and later lower testosterone levels, as a juvenile, may lead the male to develop into an orange type.[17] During dry weather conditions, orange-type males' corticosterone levels increase, which causes testosterone to decrease, leading them to be more likely to leave their territory and become nomadic. Orange-blue males do not have this hormonal response to the weather, and remain in their territories regardless of climatic conditions.[16]

Subspecies

Ten subspecies are recognized as being valid, including the nominotypical subspecies.[2]

Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Urosaurus.

Geographic range

United States: California, Nevada, Utah, Colorado, Wyoming,[18] Arizona, New Mexico, and Texas.
Mexico: Sonora, Sinaloa, Chihuahua, and Coahuila.

References

  1. ↑ Global Reptile Assessment Coordinating Team (2007). "Urosaurus ornatus". IUCN Red List of Threatened Species. Version 2009.1. International Union for Conservation of Nature. Retrieved 10 July 2009. Database entry includes justification for why this species is of least concern.
  2. 1 2 "Urosaurus ornatus ". The Reptile Database. www.reptile-database.org.
  3. ↑ Matt KS, Moore MC, Knapp R, Moore IT (1997). "Sympathetic mediation of stress and aggressive competition: plasma catecholamines in free-living male tree lizards". Physiology and Behavior. 61 (5): 639–647. doi:10.1016/S0031-9384(96)00500-8. PMID 9145930.
  4. ↑ Jennings DH, Moore MC, Knapp R, Matthews L, Orchinik M (2000). "Plasma steroid-binding globulins mediate stress reactivity in the tree lizard, Urosaurus ornatus ". General and Comparative Endocrinology 120: 289-299.
  5. ↑ Landwer, Allan J. (December 1994). "Manipulation of egg production reveals costs of reproduction in the tree lizard (Urosaurus ornatus)". Oecologia. 100 (3): 243–9. doi:10.1007/BF00316951.
  6. ↑ French SS, Moore MC (2008). "Immune function varies with reproductive stage and context in female and male tree lizards, Urosaurus ornatus ". General and Comparative Endocrinology 155 (1): 148-156.
  7. 1 2 Hews DK, Thompson CW, Moore IT, Moore MC (1997). "Population frequencies of alternative male phenotypes in tree lizards: geographic variation and common-garden rearing studies". Behavioral Ecology and Sociobiology 41: 371-380.
  8. ↑ Moore MC, Hews DK, Knapp R (1998). "Hormonal control and evolution of alternative male phenotypes: generalizations of models for sexual differentiation". American Zoologist 38: 133-151.
  9. ↑ Weiss SL, Moore MC (2004). "Activation of aggressive behavior by progesterone and testosterone in male tree lizards, Urosaurus ornatus ". Gen. Comp. Endocrinol. 136 (2): 282–288.
  10. ↑ M'Closkey RT, Baia KA, Russell RW (1987). "Tree lizard (Urosaurus ornatus) territories: experimental perturbation of the sex ratio". Ecology 68 (6): 2059-2062.
  11. ↑ Zucker N, Boecklen W (1990). "Variation in female throat coloration in the tree lizard (Urosaurus ornatus): Relation to reproductive cycle and fecundity". Herpetologica 46 (4): 387-394.
  12. ↑ Lattanzio M, Metro KJ, Miles DB (2014). "Preference for male traits differ in two female morphs of the tree lizard, Urosaurus ornatus ". PLoS ONE 9 (7): e101515. doi: 10.1371/journal.pone.0101515
  13. ↑ Stebbins RC (2003). A Field Guide to Western Reptiles and Amphibians. (Peterson Field Guides). 3rd Edition.
  14. ↑ Thompson CW, Moore MC (1991). "Syntopic occurrence of multiple dewlap color morphs in male tree lizards, Urosaurus ornatus ". Copeia 1991 (2): 493-503.
  15. ↑ Thompson CW, Moore MC (1991). "Throat colour reliably signals status in male tree lizards, Urosaurus ornatus ". Animal Behaviour 42 (5): 745-753.
  16. 1 2 Knapp R, Hews DK, Thompson CW, Ray LE, Moore MC (2003). "Environmental and endocrine correlates of tactic switching by non-territorial male tree lizards, Urosaurus ornatus ". Hormones and Behavior 43: 83-92.
  17. ↑ Hews DK, Knapp R, Moore MC (1994). "Early exposure to androgens affects adult expression of alternative male types in tree lizards". Hormones and Behavior 28: 96-115.
  18. ↑ Herpedia: The Reptiles and Amphibians of Wyoming

Further reading

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