Oecologia

, Volume 94, Issue 1, pp 102–109

Island/mainland body size differences in Australian varanid lizards

  • Ted J. Case
  • Terry D. Schwaner
Original Papers

Abstract

Island varanids seem to be an exception to the rule that territorial vertebrate taxa often become gigantic relative to mainland relatives when on islands, whereas non-territorial species become dwarfed (Case 1978). However, no systematic island/mainland studies have examined the empirical size trends in this group of carnivorous lizards. We perform such an analysis for the Australian region and critically evaluate various selective agents that might be responsible for size changes in several island populations. Insular gigantism occurs at least four times among the island populations examined. The magnitude of size change is positively correlated to prey abundance on the islands (as indirectly measured through a condition index of the lizards, essentially a measure of how fat they arc) and the size of prey: islands with large prey have large varanids and vice versa. Since the island population with the largest size change, the Reevesby Varanus rosenbergi, was introduced less than 100 years ago, these size changes can be quite rapid. This might indicate that selective coefficients are strong; however, we can not exclude the possibility that these size differences have no genetic component and simply reflect environmental differences in growth rate and shifts in age structure between island and mainland locations.

Key words

Lizards Islands Gigantism Varanus 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Andrewartha HG, Browning TO (1961) An analysis of the idea of “resources” in animal ecology. J Theoret Biol 1: 83–97Google Scholar
  2. Andrews RM (1979) Evolution of life histories: a comparison of Anolis lizards from matched island and mainland habitats. Breviora; 454: 1–51Google Scholar
  3. Andrews RM (1982) Patterns of growth in reptiles. In: Gans C, Pough FH (eds), Biology of the Reptilia, vol 13. Academic Press, New York, pp. 273–320Google Scholar
  4. Angerbjörn A (1986) Gigantism in island populations of wood mice (Apodemus) in Europe. Oikos 47: 47–56Google Scholar
  5. Auffenberg W (1981) The behavioral ecology of the Komodo Monitor. University of Florida Press, GainesvilleGoogle Scholar
  6. Barlow JC (1973) Status of the North American population of the European tree sparrow. Ornithol Monog 14: 10–23Google Scholar
  7. Barnett B, Schwaner TD (1985) Growth in captive born tiger snakes (Notechis ater serventyi) from Chappel Island: Implications for field and laboratory studies. Trans Royal Soc S Austr 109: 31–36Google Scholar
  8. Brattsrom BH (1974) The evolution of reptilian social behavior. Am Zool 14: 35–49Google Scholar
  9. Butler WH (1970) A summary of the vertebrate fauna of Barrow Island. West Aust Nat 11: 149–159Google Scholar
  10. Butler WH (1975) Additions to the fauna of Barrow Island. West Aust Nat 78–81Google Scholar
  11. Carlquist S (1965) Island life: a natural history of the islands of the world. Natur Hist Press, Garden City, NYGoogle Scholar
  12. Case TJ (1975) Species numbers, density compensation, and colonizing ability of lizards on islands in the Gulf on California. Ecology 56: 3–18Google Scholar
  13. Case TJ (1976) Body size differences between populations of the chuckwalla, Sauromalus obesus. Ecology 57: 313–323Google Scholar
  14. Case TJ (1978) A general explanation for insular body size trends in terrestrial vertebrates. Ecology 59: 1–18Google Scholar
  15. Case TJ (1982) Ecology and evolution of the insular gigantic Sauromalus. In: Burghardt G, Rand AS (eds), Iguanas of the world. Noyes Publ, Park Ridge, NJ, pp 184–212Google Scholar
  16. Dunham AE (1978) Food availability as a proximate factor influencing individual growth rates in the iquanid lizard Sceloporus merriami. Ecology 59: 770–778Google Scholar
  17. Foster JB (1964) Evolution of mammals on islands. Nature 202: 234–235Google Scholar
  18. Fraser AJ (1962) An expedition to Bernier and Dorre Islands. West Aust Fisheries Dept. Fauna Bull No. 2Google Scholar
  19. Green B, King D (1978) Home range and activity patterns of the sand goanna, Varanus gouldii (Reptilia: Varanidae). Aust J Wildlife Res 5: 417–424Google Scholar
  20. Heatwole H, Butler H (1981) Structure of an assemblage of lizards on Barrow Island, Western Australia. Aust J Herp 1: 37–44Google Scholar
  21. Hecht MK (1975) The morphology and relationships of the largest known terrestrial lizard, Megalania prisca Owen, from the Pleistocene of Australia. Proc Royal Soc. Victoria 87: 239–249Google Scholar
  22. Hooijer DA (1951) Pygmy elephant and giant tortoise. Sci. Monthly 72: 3–8Google Scholar
  23. James CD, Losos JB, and King DR (1992) Reproductive biology and diets of goannas (Reptilia: Varanidae) from Australia. J Herpetol 26: 128–136Google Scholar
  24. King D, Green B (1979) Notes on diet and reproduction of the sand goanna, Varanus gouldii rosenbergi. Copeia 1979: 64–70Google Scholar
  25. Lawlor TE (1982) The evolution of body size in mammals: evidence from insular populations in Mexico. Am Nat 119: 54–72Google Scholar
  26. Lister AM (1989) Rapid dwarfing of red deer on Jersey in the last interglacial. Nature 342: 539–542Google Scholar
  27. Losos JB, and Greene HW. Ecological and evolutionary implications of diet in monitor lizards. Biol J Linn Soc 35: 379–407Google Scholar
  28. Mertens R (1934) Die Insel Reptilian. Zoologica 84: 1–205Google Scholar
  29. Pianka ER (1968) Notes of the biology of Varanus eremius. West Aust Nat 11: 39–44Google Scholar
  30. Pianka ER (1970) Notes on the biology of Varanus gouldi flavirufus. West Aust Nat 11: 141–144Google Scholar
  31. Pianka ER (1982) Observations on the ecology of Varanus in the Great Victorian Desert. West Aust Nat 15: 1–8Google Scholar
  32. Pregill GK (1986) Body size of insular lizards: A pattern of Holocene dwarfism. Evolution 40: 997–1008Google Scholar
  33. Reese DS (1989) Tracking the extinct pygmy hippopatamus of Cyprus. Field Mus Nat Hist Bull 60: 22–29Google Scholar
  34. Robinson AC, Canty PD, Mooney PA, Rudduck PM (1986) South Australia's offshore islands. Austr Natl Parks and Wildl Serv Spec Publ.Google Scholar
  35. Robinson AC, Mirtschin PJ, Copley PD, Canty PD, Jenkins RB (1985) The Reevesby Island goanna — a problem in conservation management. S Aust Nat 59: 56–62Google Scholar
  36. Roughgarden J, Fuentes ER (1977) The environmental determinants of size in solitary populations of West Indian Anolis lizards. Oikos 29: 44–51Google Scholar
  37. Schoener TW (1969) Models of optimal size for solitary predators. Am Nat 103: 277–313Google Scholar
  38. Schoener TW (1969) Size patterns in West Indian Anolis lizards I. Size and specific diversity. Syst Zool 18: 386–401Google Scholar
  39. Schoener TW (1970) Size patterns in West Indian Anolis lizards II. Correlations with the sizes of particular sympatric species-displacement nad convergence. Am Nat 104: 155–174Google Scholar
  40. Schoener TW, Schoener A (1978) Estimating and interpreting body-size growth in some Anolis lizards. Copeia 1978: 390–405Google Scholar
  41. Schoener TW, Schoener A (1980) Densities, sex ratios, and population structure in four species of Bahamian Anolis lizards. J Anim Ecol 49: 19–53Google Scholar
  42. Schwaner TD (1985) Population structure of black tiger snakes, Notechis ater niger, on offshore islands of South Australia. In: Grigg G, Shine R, Ehrmann H (eds), Biology of Australian frogs and reptiles. Surrey Beatty and Sons, Sydney, pp 35–36Google Scholar
  43. Schwaner TD (1990) Geographic variation in scale and skeletal anomalies of tiger snakes (Elapidae: Notechis scutatus-ater complex) in Southern Australia. Copeia 1990: 1138–1143Google Scholar
  44. Schwaner TD, Sarre SD (1988) Body size of tiger snakes in Southern Australia, with particular reference to Notechis ater serventyi. J Herpetol 22: 24–33Google Scholar
  45. Schwaner TD, Sarre SD (1990) Body size and sexual dimorphism in mainland and island tiger snakes. J Herpetol 24: 320–323Google Scholar
  46. Shine R (1986) Food habits, habitats and reproductive biology of four sympatric species of varanid lizards in tropical Australia. Herpetologica 42: 346–360Google Scholar
  47. Shine R (1987) Ecological comparisons of island and mainland populations of Australian tigersnakes (Notechis: Elapidae). Herpetologica 43: 233–240Google Scholar
  48. Smith LA (1976) Reptiles of Barrow Island. West Aust Nat 13: 85–108Google Scholar
  49. Soulé M (1966) Trends in the insular radiation of a lizard. Am Midl Nat 100: 47–64Google Scholar
  50. St. Louis VL, Barlow JC (1988) Genetic differentiation among ancestral and introduced populations of the Eurasian tree sparrow (Passer montanus). Evolution 42: 266–276Google Scholar
  51. Stamps JA (1983) Sexual selection, sexual dimorphism, and territoriality. In: Huey RB, Pianka ER, Schoener TW (eds), Lizard ecology: studies of a model organism. Harvard Univ. Press, Cambridge, MA, pp 169–204Google Scholar
  52. Storr GM (1980) The monitor lizards (genus Varanus Merrem, 1820) of western Australia. Rec West Aust Mus 8: 237–293Google Scholar
  53. Tindale NB (1924) Visit to the islands of the Sir Joseph Banks Group. S Aust Natur 5: 130–132Google Scholar
  54. Williams V, White J, Schwaner TD, Sparrow A (1988) Variation in venom proteins from isolated populations of tiger snakes (Notechis ater niger, N. scutatus). Toxicon 26: 1067–1075Google Scholar

Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Ted J. Case
    • 1
  • Terry D. Schwaner
    • 2
  1. 1.Department of Biology, C-016University of California at San DiegoLa JollaUSA
  2. 2.Alabama School of Mathematics and ScienceMobileUSA

Personalised recommendations