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.

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. Bibcode:2003ANat..162..332A. 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.
  5. Ashton, Kyle G (2002-04-01). "Do amphibians follow Bergmann's rule?". Canadian Journal of Zoology. 80 (4): 708–716. Bibcode:2002CaJZ...80..708A. doi:10.1139/z02-049. ISSN   0008-4301.
  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.
  8. 1 2 3 Sibly, Richard M.; Atkinson, David (1997-06-01). "Why are organisms usually bigger in colder environments? Making sense of a life history puzzle" . Trends in Ecology & Evolution. 12 (6): 235–239. Bibcode:1997TEcoE..12..235A. doi:10.1016/S0169-5347(97)01058-6. ISSN   0169-5347. PMID   21238056.
  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.
  10. 1 2 3 Angilletta, Michael J.; Sears, Michael W. (2004-12-01). "Body Size Clines in Sceloporus Lizards: Proximate Mechanisms and Demographic Constraints". Integrative and Comparative Biology. 44 (6): 433–442. doi: 10.1093/icb/44.6.433 . ISSN   1540-7063. PMID   21676729.
  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. Bibcode:2006ANat..167..510W. doi:10.1086/501029. ISSN   0003-0147. PMID   16670994. S2CID   37958226.
  13. Atkinson, D. (1994), Temperature and Organism Size—A Biological Law for Ectotherms? , Advances in Ecological Research, vol. 25, Elsevier, pp. 1–58, doi:10.1016/s0065-2504(08)60212-3, ISBN   9780120139255 , retrieved 2019-04-15
  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. Bibcode:1993ANat..142..273A. 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. Bibcode:1986ANat..128..137V. 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.