Temperature-size rule

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The temperature-size rule denotes the plastic response (i.e. phenotypic plasticity) of organismal body size to environmental temperature variation. [1] [2] Organisms exhibiting a plastic response are capable of allowing their body size to fluctuate with environmental temperature. First coined by David Atkinson in 1996, [3] it is considered to be a unique case of Bergmann's rule [1] that has been observed in plants, animals, birds, and a wide variety of ectotherms. [2] [4] [5] [6] [7] Although exceptions to the temperature-size rule exist, recognition of this widespread "rule" has amassed efforts to understand the physiological mechanisms (via possible tradeoffs) underlying growth and body size variation in differing environmental temperatures. [2] [8]

Contents

History

Comparative photo of a northern red fox and southern desert red fox depicting size differences with increasing latitudes (i.e. Bergmann's rule). Northern red fox & southern desert red fox.jpg
Comparative photo of a northern red fox and southern desert red fox depicting size differences with increasing latitudes (i.e. Bergmann's rule).

Relation to Bergmann's rule

In 1847, Carl Bergmann published his observations that endothermic body size (i.e. mammals) increased with increasing latitude, commonly known as Bergmann's rule. [9] His rule postulated that selection favored within species individuals with larger body sizes in cooler temperatures because the total heat loss would be diminished through lower surface area to volume ratios. [8] However, ectothermic individuals thermoregulate and allow their internal body temperature to fluctuate with environmental temperature whereas endotherms maintain a constant internal body temperature. This creates an inaccurate description of observed body size variation in ectotherms since they routinely allow evaporative heat loss and do not maintain constant internal temperatures. [8] [10] Despite this, ectotherms have largely been observed to still exhibit larger body sizes in colder environments.

Formulation of the rule

Ray (1960) originally examined body sizes in several species of ectotherms and discovered that around 80% of them exhibited larger body sizes in lower temperatures. [11] A few decades later, Atkinson (1994) performed a similar review of temperature effects on body size in ectotherms. His study, which included 92 species of ectotherms ranging from animals and plants to protists and bacteria, concluded that a reduction in temperature resulted in an increase in organism size in 83.5% of cases. [11] [12] [13] Atkinson's findings provided support for Ray's published works that ectotherms have an observable trend in body size when temperature is the primary environmental variable. The results of his study prompted him to name the increase in ectothermic body size in colder environments as the temperature-size rule.

Tradeoffs as possible underlying mechanisms

Life history model

Life history models highlighting optimal growth patterns suggest that individuals assess the environment for potential resources and other proximate factors and mature at a body size that yields the greatest reproductive success, or highest percentage of offspring surviving to reach reproductive maturity. [14]

Size at maturity

Environmental temperature is one of the most important proximate factors affecting ectotherm body size because of their need to thermoregulate. Individuals that have been observed to follow the temperature-size rule have slower growth rates in colder environments, yet they enter a period of prolonged growth that yields larger adult body sizes. [3] [15] [16] One proposed explanation for this involves a trade-off in life history traits. Ectotherms experience longer daily and seasonal activity times in warmer climates versus cooler climates, however, the increase in daily activity time is accompanied by higher infant and adult mortality rates due to predation. [16] [17] Under these environmental conditions, some individuals occupying these warmer climate environments will mature at smaller body sizes and undergo a shift in energy allocation of all acquired energy resources to reproduction. [18] [19] [20] In doing so, these individuals sacrifice growth to larger adult body sizes to ensure reproductive success, even if the trade-off results in smaller offspring that have increased mortality rates. [20]

Reproduction

Ectotherms occupying colder environments, such as mountain ranges or other areas of higher elevation, have been observed to invest in reproduction at larger adult body sizes due to a prolonged growth period. These populations of ectotherms are characterized as having smaller clutches of larger eggs, favoring a greater reproductive investment per egg and enhances offspring survival rates. [21] Individuals occupying warmer environments experience a trade-off between body size and overall reproductive success that many individuals occupying colder environments do not, hence, prolonging growth to yield greater reproductive success in colder environments could potentially be an underlying mechanism for why a large percentage of ectotherms exhibit greater body sizes in colder environments. However, a sufficient explanation for this observable pattern has yet to be produced. [14]

Investigation

Common lizard (Lacerta vivipara). Common Lizard. Lacerta vivipara (27742089869).jpg
Common lizard (Lacerta vivipara).

Supporting evidence

Eastern fence lizard (Sceloporus undulatus). Sceloporus undulatus1.JPG
Eastern fence lizard (Sceloporus undulatus).

Exceptions

Notes

The supporting evidence and the exceptions to the temperature-size rule listed above are only a few of the potential supporting/opposing evidence available for the temperature-size rule. Each was provided to support the claim that patterns of body size observed in variable environments are not 100% predictable and more research is required to identify and understand all of the mechanisms responsible.

Related Research Articles

<span class="mw-page-title-main">Endotherm</span> Organism that maintains body temperature largely by heat from internal bodily functions

An endotherm is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions instead of relying almost purely on ambient heat. Such internally generated heat is mainly an incidental product of the animal's routine metabolism, but under conditions of excessive cold or low activity an endotherm might apply special mechanisms adapted specifically to heat production. Examples include special-function muscular exertion such as shivering, and uncoupled oxidative metabolism, such as within brown adipose tissue.

<span class="mw-page-title-main">Thermoregulation</span> Ability of an organism to keep its body temperature within certain boundaries

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its own body temperature, thus avoiding the need for internal thermoregulation. The internal thermoregulation process is one aspect of homeostasis: a state of dynamic stability in an organism's internal conditions, maintained far from thermal equilibrium with its environment. If the body is unable to maintain a normal temperature and it increases significantly above normal, a condition known as hyperthermia occurs. Humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35 °C (95 °F) for six hours.

<span class="mw-page-title-main">Ectotherm</span> Organism where internal heating sources are small or negligible

An ectotherm, more commonly referred to as a "cold-bloodedanimal", is an animal in which internal physiological sources of heat, such as blood, are of relatively small or of quite negligible importance in controlling body temperature. Such organisms rely on environmental heat sources, which permit them to operate at very economical metabolic rates.

<span class="mw-page-title-main">Bergmann's rule</span> Biological rule stating that larger size organisms are found in colder environments

Bergmann's rule is an ecogeographical rule that states that, within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, while populations and species of smaller size are found in warmer regions. The rule derives from the relationship between size in linear dimensions meaning that both height and volume will increase in colder environments. Bergmann's rule only describes the overall size of the animals, but does not include body proportions like Allen's rule does.

<span class="mw-page-title-main">Viviparous lizard</span> Species of lizard

The viviparous lizard, or common lizard, is a Eurasian lizard. It lives farther north than any other species of non-marine reptile, and is named for the fact that it is viviparous, meaning it gives birth to live young. Both "Zootoca" and "vivipara" mean "live birth", in (Latinized) Greek and Latin respectively. It was called Lacerta vivipara until the genus Lacerta was split into nine genera in 2007 by Arnold, Arribas & Carranza.

<span class="mw-page-title-main">Allen's rule</span> Relation of habitat temperature and limb length

Allen's rule is an ecogeographical rule formulated by Joel Asaph Allen in 1877, broadly stating that animals adapted to cold climates have shorter and thicker limbs and bodily appendages than animals adapted to warm climates. More specifically, it states that the body surface-area-to-volume ratio for homeothermic animals varies with the average temperature of the habitat to which they are adapted.

<span class="mw-page-title-main">Darwin's frog</span> Species of amphibian

Darwin’s frog, also called the Southern Darwin's frog, is a species of Chilean/Argentinian frog of the family Rhinodermatidae. It was discovered by Charles Darwin during his voyage on HMS Beagle. on a trip to Chile. In 1841, French zoologist André Marie Constant Duméril and his assistant Gabriel Bibron described and named Darwin's frog. The diet of R. darwinii consists mostly of herbivore invertebrates. R. darwinii is currently classified as an endangered species by the International Union for Conservation of Nature.

<i>Urosaurus ornatus</i> Species of lizard

Urosaurus ornatus, commonly known as the ornate tree lizard, is a species of lizard in the family Phrynosomatidae. The species is native to the southwestern United States and northwestern Mexico. The species, which was formerly 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. Its life history and costs of reproduction have been documented in field populations in New Mexico and Arizona. This species has been fairly well studied because of its interesting variation in throat color in males that can correlate with different reproductive strategies,

<span class="mw-page-title-main">Sagebrush lizard</span> Species of lizard

The sagebrush lizard or sagebrush swift is a common species of phrynosomatid lizard found at mid to high altitudes in the western United States. It belongs to the genus Sceloporus in the Phrynosomatidae family of reptiles. Named after the sagebrush plants near which it is commonly found, the sagebrush lizard has keeled and spiny scales running along its dorsal surface.

Climatic adaptation refers to adaptations of an organism that are triggered due to the patterns of variation of abiotic factors that determine a specific climate. Annual means, seasonal variation and daily patterns of abiotic factors are properties of a climate where organisms can be adapted to. Changes in behavior, physical structure, internal mechanisms and metabolism are forms of adaptation that is caused by climate properties. Organisms of the same species that occur in different climates can be compared to determine which adaptations are due to climate and which are influenced majorly by other factors. Climatic adaptations limits to adaptations that have been established, characterizing species that live within the specific climate. It is different from climate change adaptations which refers to the ability to adapt to gradual changes of a climate. Once a climate has changed, the climate change adaptation that led to the survival of the specific organisms as a species can be seen as a climatic adaptation. Climatic adaptation is constrained by the genetic variability of the species in question.

<span class="mw-page-title-main">Argentine black and white tegu</span> Species of lizard which is the largest of the tegu lizards

The Argentine black and white tegu, also known as the Argentine giant tegu, the black and white tegu, or the huge tegu, is a species of lizard in the family Teiidae. The species is the largest of the "tegu lizards". It is an omnivorous species which inhabits the tropical rain forests, savannas and semi-deserts of eastern and central South America. They are native to southeastern Brazil, Uruguay, eastern Paraguay, and Argentina.

In biology, a cline is a measurable gradient in a single characteristic of a species across its geographical range. Clines usually have a genetic, or phenotypic character. They can show either smooth, continuous gradation in a character, or more abrupt changes in the trait from one geographic region to the next.

<span class="mw-page-title-main">Eastern three-lined skink</span> Species of lizard

The eastern three-lined skink, also known commonly as the bold-striped cool-skink, is a species of skink, a lizard in the family Scincidae. The species is endemic to Australia. A. duperreyi has been extensively studied in the context of understanding the evolution of learning, viviparity in lizards, and temperature- and genetic-sex determination. A. duperreyi is classified as a species of "Least Concern" by the IUCN.

<span class="mw-page-title-main">Deep-sea gigantism</span> Tendency for deep-sea species to be larger than their shallower-water relatives

In zoology, deep-sea gigantism or abyssal gigantism is the tendency for species of deep-sea dwelling animals to be larger than their shallower-water relatives across a large taxonomic range. Proposed explanations for this type of gigantism include necessary adaptation to colder temperature, food scarcity, reduced predation pressure and increased dissolved oxygen concentrations in the deep sea. The harsh conditions and inhospitality of the underwater environment in general, as well as the inaccessibility of the abyssal zone for most human-made underwater vehicles, have hindered the study of this topic.

<span class="mw-page-title-main">Kleptothermy</span> Form of thermoregulation in which an animal shares in the heat production of another

In biology, kleptothermy is any form of thermoregulation by which an animal shares in the metabolic thermogenesis of another animal. It may or may not be reciprocal, and occurs in both endotherms and ectotherms. One of its forms is huddling. However, kleptothermy can happen between different species that share the same habitat, and can also happen in pre-hatching life where embryos are able to detect thermal changes in the environment.

<span class="mw-page-title-main">Mesotherm</span> Type of animal that produces metabolic heat, but has no specific body temperature

A mesotherm is a type of animal with a thermoregulatory strategy intermediate to cold-blooded ectotherms and warm-blooded endotherms.

<span class="mw-page-title-main">Biological rules</span> Generalized principle to describe patterns observed in living organisms

A biological rule or biological law is a generalized law, principle, or rule of thumb formulated to describe patterns observed in living organisms. Biological rules and laws are often developed as succinct, broadly applicable ways to explain complex phenomena or salient observations about the ecology and biogeographical distributions of plant and animal species around the world, though they have been proposed for or extended to all types of organisms. Many of these regularities of ecology and biogeography are named after the biologists who first described them.

Countergradient variation is a type of phenotypic plasticity that occurs when the phenotypic variation determined by a biological population's genetic components opposes the phenotypic variation caused by an environmental gradient. This can cause different populations of the same organism to display similar phenotypes regardless of their underlying genetics and differences in their environments.

Thermal ecology is the study of the interactions between temperature and organisms. Such interactions include the effects of temperature on an organism's physiology, behavioral patterns, and relationship with its environment. While being warmer is usually associated with greater fitness, maintaining this level of heat costs a significant amount of energy. Organisms will make various trade-offs so that they can continue to operate at their preferred temperatures and optimize metabolic functions. With the emergence of climate change scientists are investigating how species will be affected and what changes they will undergo in response.

<i>Phrynocephalus vlangalii</i> Species of reptile

Phrynocephalus vlangalii, also known as the Qinghai toad-headed agama, the Ching Hai toadhead agama, the Pylzow's toadhead agama, or gecko toadhead agama, is a species of viviparous agamid lizard endemic to the Tibetan Plateau in China. This lizard lives in burrows at high elevations of 2,000 to 4,600 meters. It is also known for its aggression, especially between females during mating season since females usually only have one mate. P. vlangalii curls its tail and shows a patch on its underbelly as defense displays against conspecifics. This lizard also has a variety of gut microbiota that help perform metabolic and biological functions depending on the altitude at which the lizard lives.

References

  1. 1 2 Angilletta, Jr.,, Michael J.; Dunham, Arthur E. (2003-09-01). "The Temperature-Size Rule in Ectotherms: Simple Evolutionary Explanations May Not Be General". The American Naturalist. 162 (3): 332–342. doi:10.1086/377187. ISSN   0003-0147. PMID   12970841. S2CID   23553079.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. 1 2 3 Sears, Michael W.; Steury, Todd D.; Angilletta, Michael J. (2004-12-01). "Temperature, Growth Rate, and Body Size in Ectotherms: Fitting Pieces of a Life-History Puzzle". Integrative and Comparative Biology. 44 (6): 498–509. doi: 10.1093/icb/44.6.498 . ISSN   1540-7063. PMID   21676736.
  3. 1 2 Dańko, M.; Czarnołęski, M.; Kozłowski, J. (2004-12-01). "Can Optimal Resource Allocation Models Explain Why Ectotherms Grow Larger in Cold?". Integrative and Comparative Biology. 44 (6): 480–493. doi: 10.1093/icb/44.6.480 . ISSN   1540-7063. PMID   21676734.
  4. ↑ Ashton, Kyle G. (2001). "Are ecological and evolutionary rules being dismissed prematurely?". Diversity and Distributions. 7 (6): 289–295. Bibcode:2001DivDi...7..289A. doi: 10.1046/j.1366-9516.2001.00115.x . ISSN   1472-4642. S2CID   85759222.
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  6. ↑ Ashton, Kyle G. (2002). "Patterns of within-species body size variation of birds: strong evidence for Bergmann's rule". Global Ecology and Biogeography. 11 (6): 505–523. Bibcode:2002GloEB..11..505A. doi:10.1046/j.1466-822X.2002.00313.x. ISSN   1466-8238.
  7. 1 2 3 4 Ashton, Kyle G.; Feldman, Chris R. (2003). "BERGMANN's RULE IN NONAVIAN REPTILES: TURTLES FOLLOW IT, LIZARDS AND SNAKES REVERSE IT". Evolution. 57 (5): 1151–1163. doi:10.1111/j.0014-3820.2003.tb00324.x. ISSN   1558-5646. PMID   12836831. S2CID   11526767.
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  9. ↑ Blackburn, Tim M.; Gaston, Kevin J.; Loder, Natasha (1999). "Geographic gradients in body size: a clarification of Bergmann's rule". Diversity and Distributions. 5 (4): 165–174. doi: 10.1046/j.1472-4642.1999.00046.x . ISSN   1472-4642. S2CID   82102916.
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  11. 1 2 3 Voorhies, Wayne A. Van (1996). "Bergmann Size Clines: A Simple Explanation for Their Occurrence in Ectotherms". Evolution. 50 (3): 1259–1264. doi:10.1111/j.1558-5646.1996.tb02366.x. ISSN   1558-5646. PMID   28565268. S2CID   140130311.
  12. 1 2 Walters, Richard John; Hassall, Mark (2006-04-01). "The Temperature-Size Rule in Ectotherms: May a General Explanation Exist after All?". The American Naturalist. 167 (4): 510–523. doi:10.1086/501029. ISSN   0003-0147. PMID   16670994. S2CID   37958226.
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  14. 1 2 Berrigan, D.; Charnov, E. L. (1994). "Reaction Norms for Age and Size at Maturity in Response to Temperature: A Puzzle for Life Historians". Oikos. 70 (3): 474–478. Bibcode:1994Oikos..70..474B. doi:10.2307/3545787. ISSN   0030-1299. JSTOR   3545787.
  15. ↑ Sears, Michael W. (2005-03-01). "Geographic variation in the life history of the sagebrush lizard: the role of thermal constraints on activity". Oecologia. 143 (1): 25–36. Bibcode:2005Oecol.143...25S. doi:10.1007/s00442-004-1767-0. ISSN   1432-1939. PMID   15742218. S2CID   26809726.
  16. 1 2 3 Arnett, Amy E.; Gotelli, Nicholas J. (1999). "Geographic Variation in Life-History Traits of the Ant Lion, Myrmeleon Immaculatus: Evolutionary Implications of Bergmann's Rule". Evolution. 53 (4): 1180–1188. doi: 10.1111/j.1558-5646.1999.tb04531.x . ISSN   1558-5646. PMID   28565522. S2CID   19745749.
  17. ↑ Adolph, Stephen C.; Porter, Warren P. (1993-08-01). "Temperature, Activity, and Lizard Life Histories". The American Naturalist. 142 (2): 273–295. doi:10.1086/285538. ISSN   0003-0147. PMID   19425979. S2CID   22543201.
  18. ↑ van Noordwijk, A. J.; de Jong, G. (1986-07-01). "Acquisition and Allocation of Resources: Their Influence on Variation in Life History Tactics". The American Naturalist. 128 (1): 137–142. doi:10.1086/284547. hdl: 20.500.11755/8748e681-f8e9-4fed-a6be-39723fbaf955 . ISSN   0003-0147. S2CID   222332253.
  19. ↑ Kozłowski, J. (1992). "Optimal allocation of resources to growth and reproduction: Implications for age and size at maturity". Trends in Ecology & Evolution. 7 (1): 15–9. Bibcode:1992TEcoE...7...15K. doi:10.1016/0169-5347(92)90192-e. PMID   21235937.
  20. 1 2 Stearns, Stephen C. (1992). The evolution of life histories. New York: Oxford University Press. pp. 1–89.
  21. ↑ Badyaev, Alexander V.; Ghalambor, Cameron K. (2001). "Evolution of Life Histories Along Elevational Gradients: Trade-Off Between Parental Care and Fecundity". Ecology. 82 (10): 2948–2960. doi:10.1890/0012-9658(2001)082[2948:EOLHAE]2.0.CO;2. ISSN   1939-9170.
  22. ↑ Sorci, Gabriele; Clobert, Jean; Belichon, Sophie (1996). "Phenotypic Plasticity of Growth and Survival in the Common Lizard Lacerta vivipara". Journal of Animal Ecology. 65 (6): 781–790. Bibcode:1996JAnEc..65..781S. doi:10.2307/5676. ISSN   0021-8790. JSTOR   5676.
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