Variation in scale numbers is consistent with ecologically based natural selection acting within and between lizard species |
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Authors: | Ryan Calsbeek Jason H. Knouft Thomas B. Smith |
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Affiliation: | (1) Center for Tropical Research, Institute of the Environment, University of California, 1609 Hershey Hall, Los Angeles, CA 90065-1497, USA;(2) Department of Biology, Washington University, Campus Box 1137, St. Louis, MO 63130-4899, USA;(3) Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90065-1497, USA;(4) Zoology Section, University of Colorado Museum and Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA;(5) Present address: Dept of Biological Sciences, Dartmonth College, Hanover, NH 03755, USA |
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Abstract: | Recent studies have demonstrated that changes in scale number are correlated with ecological variables such as precipitation, and this suggests that scale number may be under selection to maintain water balance in reptiles. Here, we present new evidence that variation in scale numbers within and among species of Anolis lizards is under ecologically based natural selection. We measured scalation of the brown anole, Anolis sagrei, in two habitat types on each of five islands in the Bahamas. We also measured scalation for 12 species of anole representing six different ecomorphs from the Greater Antilles. Within populations of A. sagrei, scale numbers increased with increasing precipitation and with decreasing temperature in open arid habitats. Variation measured among species of Anolis from the Greater Antilles showed similar patterns with temperature, precipitation, and elevation. Independent contrasts using scale count data indicated that variation in scale number was congruent within and between species, even after accounting for the influence of phylogeny. We measured natural selection (survival to maturity) on scale number in A. sagrei over two different habitat types in the Bahamas. Patterns of natural selection were congruent with the correlational results described. Finally, results from a breeding experiment in the laboratory provide preliminary evidence that variation in scale number is heritable, and suggests a mechanism for generating these correlations. Our results provide new evidence that the diversification of anoles has been shaped by natural selection and that ecologically based selection pressures help explain diversification at both the population and species levels. Co-ordinating editor: M. Klaassen |
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Keywords: | adaptive radiation independent contrasts lizard micro-climate natural selection scalation selection |
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