Common side-blotched lizard
Encyclopedia
The common side-blotched lizard (Uta stansburiana) is a species of side-blotched lizard
common on the Pacific coast of North America
, from Washington to western Texas
and NW Mexico
. It has a peculiar evolutionary strategy following the pattern of the game of
Rock, Paper, Scissors, with three types of males existing, each of which applies a different technique to acquire mates (Sinervo & Lively, 1996; Sinervo, 2001; Alonzo & Sinervo, 2001; Sinervo & Clobert, 2001; Sinervo & Zamudio, 2001).
The specific epithet, stansburiana, is in honor of Captain Howard Stansbury
of the United States Corps of Topographical Engineers, who collected the first specimens while leading the 1849-1851 expedition to explore and survey the Great Salt Lake
of Utah
.
The systematics and taxonomy
of these widespread and variable lizards is much disputed (Grismer, 1994; Upton & Murphy, 1997). Countless forms and morphs have been described as subspecies or even distinct species (e.g. Schmidt, 1921).
has discovered a rock-paper-scissors
strategy in the mating behaviour of the side-blotched lizard
species Uta stansburiana. Males have either orange, blue or yellow throats and each type follows a fixed, heritable mating strategy:
This can be summarized as "orange beats blue, blue beats yellow, and yellow beats orange", which is similar to the rules of rock-paper-scissors.
The proportion of each male type in a population
is similar in the long run, but fluctuates widely in the short term. For periods of 4–5 years, one strategy predominates, after which it declines in frequency as the strategy that manages to exploit its weakness increases. This corresponds to the stable pattern of the game in the replicator dynamics where the dynamical system
follows closed orbits around the mixed strategy Nash equilibrium
(Sinervo & Lively, 1996; Sinervo, 2001; Alonzo & Sinervo, 2001; Sinervo & Clobert, 2003; Sinervo & Zamudio, 2001).
Side-blotched lizard
Side-blotched lizards are lizards of the genus Uta. They are some of the most abundant and commonly observed lizards in the deserts of western North America. They commonly grow to six inches including the tail, with the males normally being the larger sex. Males often have bright throat colors....
common on the Pacific coast of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, from Washington to western Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
and NW Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. It has a peculiar evolutionary strategy following the pattern of the game of
Rock, Paper, Scissors, with three types of males existing, each of which applies a different technique to acquire mates (Sinervo & Lively, 1996; Sinervo, 2001; Alonzo & Sinervo, 2001; Sinervo & Clobert, 2001; Sinervo & Zamudio, 2001).
The specific epithet, stansburiana, is in honor of Captain Howard Stansbury
Howard Stansbury
Howard Stansbury was a major in the U.S. Army Corps of Topographical Engineers. His most notable achievement was leading a two-year expedition to survey the Great Salt Lake and its surroundings...
of the United States Corps of Topographical Engineers, who collected the first specimens while leading the 1849-1851 expedition to explore and survey the Great Salt Lake
Great Salt Lake
The Great Salt Lake, located in the northern part of the U.S. state of Utah, is the largest salt water lake in the western hemisphere, the fourth-largest terminal lake in the world. In an average year the lake covers an area of around , but the lake's size fluctuates substantially due to its...
of Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
.
Systematics
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
of these widespread and variable lizards is much disputed (Grismer, 1994; Upton & Murphy, 1997). Countless forms and morphs have been described as subspecies or even distinct species (e.g. Schmidt, 1921).
- The forms which occur in most of Mexico (except Baja CaliforniaBaja CaliforniaBaja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
) have been recognized as a very distinct species, the Eastern side-blotched lizard (Uta stejnegeri) (Collins, 1991). - Populations from San Benito and Cedros IslandCedros IslandCedros Island is a Mexican island in the Pacific Ocean....
s were separated as distinct species Uta stellata and U. concinna but are nowadays included in U. stansburiana. - Those of Santa Catalina Island and the Salsipuedes Islands, U. squamata and U. antiqua are sometimes included in this species too, but this is certainly not correct in the latter case, and probably in the former also.
- Based on the same data that would give U. squamata species rank, the southern Baja California populations could arguably be split off (as Uta elegans) too.
- The proposed subspecies martinensis and taylori are probably not valid.
- The populations on Ángel de la Guarda, Mejia and Rasa Islands almost certainly constitute a separate species closer to Uta palmeri, and that of San Esteban IslandSan Esteban IslandSan Esteban Island is a small island in the Gulf of California, Mexico, located to the southwest of Tiburón Island. It is part of the Municipality of Hermosillo in Sonora, and has a land area of 39.773 km² , the 15th-largest island in Mexico. It is located in the Sea of Cortés...
may so too, being close to squamata. - The status of the Las Encantadas group populations named as Uta encantadae, U. lowei and U. tumidarostra is not completely resolved; these distinct populations are of comparatively recent origin and are sometimes included in this species (Murphy & Aguirre-León, 2002), but their unique adaptations to living in intertidal habitat suggest that they should be considered distinct; whether as one or as three species remains unresolved.
Mating strategy
Biologist Barry Sinervo from the University of California, Santa CruzUniversity of California, Santa Cruz
The University of California, Santa Cruz, also known as UC Santa Cruz or UCSC, is a public, collegiate university; one of ten campuses in the University of California...
has discovered a rock-paper-scissors
Rock-paper-scissors
Rock-paper-scissors is a hand game played by two people. The game is also known as roshambo, or another ordering of the three items ....
strategy in the mating behaviour of the side-blotched lizard
Side-blotched lizard
Side-blotched lizards are lizards of the genus Uta. They are some of the most abundant and commonly observed lizards in the deserts of western North America. They commonly grow to six inches including the tail, with the males normally being the larger sex. Males often have bright throat colors....
species Uta stansburiana. Males have either orange, blue or yellow throats and each type follows a fixed, heritable mating strategy:
- Orange-throated males are strongest and do not form strong pair bonds; instead, they fight blue-throated males for their females. Yellow-throated males, however, manage to snatch females away from them for mating. The large size and aggression is caused by high testosterone production.
- Blue-throated males are middle-sized and form strong pair bonds. While they are outcompeted by orange-throated males, they can defend against yellow-throated ones. Because blue-throated males produce less testosterone they are not as large as the orange-throated males, but it gives them the advantage of being less aggressive and able to form strong pair bonds.
- Yellow-throated males are smallest, and their coloration mimics females. This lets them approach females near orange-throated males and mate when the males are distracted. This is less likely to work with a female that has bonded with a blue-throated male.
This can be summarized as "orange beats blue, blue beats yellow, and yellow beats orange", which is similar to the rules of rock-paper-scissors.
The proportion of each male type in a population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
is similar in the long run, but fluctuates widely in the short term. For periods of 4–5 years, one strategy predominates, after which it declines in frequency as the strategy that manages to exploit its weakness increases. This corresponds to the stable pattern of the game in the replicator dynamics where the dynamical system
Dynamical system
A dynamical system is a concept in mathematics where a fixed rule describes the time dependence of a point in a geometrical space. Examples include the mathematical models that describe the swinging of a clock pendulum, the flow of water in a pipe, and the number of fish each springtime in a...
follows closed orbits around the mixed strategy Nash equilibrium
Nash equilibrium
In game theory, Nash equilibrium is a solution concept of a game involving two or more players, in which each player is assumed to know the equilibrium strategies of the other players, and no player has anything to gain by changing only his own strategy unilaterally...
(Sinervo & Lively, 1996; Sinervo, 2001; Alonzo & Sinervo, 2001; Sinervo & Clobert, 2003; Sinervo & Zamudio, 2001).
External links
- http://www.qwantz.com/index.php?comic=1827
- UC Santa Cruz: Cooperation between unrelated male lizards adds a new wrinkle to evolutionary theory (Essay on Sinervo & Clobert 2001 paper)