Ecological shifts in sympatry: Kalahari fossorial lizards (Thyphlosaurus)

  • Huey R
  • Pianka E
  • Egan M
 et al. 
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Two species of legless, fossorial skinks (Typhlosaurus) are partially sympatric in the Kalahari Desert. Typhlosaurus lineatus occur both in the sandridge and flatland geographic provinces of the Kalahari, in dune streets and on sandridges microgeographically in sympatry, and primarily under log and leaf litter microhabitats. Typhlosaurus gariepensis, always sympatric with Typhlosaurus lineatus, occur only in sandridge areas geographically, on sandridges microgeographically, and primarily in basal roots of bunch grass microhabitats. Microhabitat overlap in sympatry is low. Morphologically, Typhlosaurus lineatus differ from Typhlosaurus gariepensis in being longer and in having a longer and wider head. Snout-vent lengths, head dimensions, and proportional head lengths of sympatric Typhlosaurus lineatus are larger than those of allopatric Typhlosaurus lineatus; thus Typhlosaurus lineatus displace from Typhlosaurus gariepensis in sympatry. Both species are viviparous, have one brood per year, and give birth in summer after a 5-mo gestation period. Maturity is reached at minimum ages of one and two-thirds yr. Mean litter size of Typhlosaurus lineatus is 1.6, whereas Typhlosaurus gariepensis have but one young. A response to competition between the two species is suggested by the facts that offspring of sympatric Typhlosaurus lineatus are significantly heavier than those of allopatric females, and that fewer sympatric Typhlosaurus lineatus females are reproductive than allopatric females. Because Typhlosaurus are termite specialists (92.4% of diet by volume), termites in guts were identified to species and caste. Compared with sympatric Typhlosaurus lineatus, Typhlosaurus gariepensis eat more Psammotermes workers, fewer Allodontermes major workers, and scarcely any Hodotermes. Sympatric Typhlosaurus lineatus eat fewer Psammotermes workers and more Allodontermes major workers than do allopatric Typhlosaurus lineatus. Prey size differences parallel lizard size differences. Because of dietary shifts by Typhlosaurus lineatus in sympatry, dietary overlap with Typhlosaurus gariepensis is substantially reduced for females and immatures, although not for males. Strong morphological and dietary evidence support, for Typhlosaurus lineatus females and immatures, the hypothesis that behavioral and morphological character displacement has occurred which reduces dietary overlap with Typhlosaurus gariepensis. Dietary data for male Typhlosaurus lineatus are possibly conflicting.

Author-supplied keywords

  • Lizard Ecology
  • Typhlosaurus
  • character displacement
  • competition
  • fossorial lizards
  • lizards
  • niche shifts
  • r and K selections
  • sympatry

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  • R B Huey

  • E R Pianka

  • M E Egan

  • L W Coons

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