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Sexual dimorphism in snake tail length: sexual selection, natural selection, or morphological constraint?

Sexual dimorphism in snake tail length: sexual selection, natural selection, or morphological... Male snakes typically have longer tails relative to body length than females, but the extent of this dimorphism varies among species. Three hypotheses have been suggested to explain tail dimorphism. The Morphological Constraint Hypothesis proposes that males have relatively longer tails to accommodate hemipenes and retractor muscles. The Female Reproductive Output Hypothesis proposes that females have relatively shorter tails as a secondary result of natural selection for increased reproductive capacity. The Male Mating Ability Hypothesis proposes that sexual selection favours relatively longer tails in males during courtship. These hypotheses make different predictions about the relationships among tail length, body size, male reproductive morphology, female reproductive output, mode of reproduction, and male mating behaviour among and within taxa. Predictions were tested using published data for 56 genera in the family Colubridae and original data for the water snake, Nerodia sipedon. Tail length dimorphism was more male‐biased in tam having relatively short tails (r=–0.52, P < 0.001), hemipenes and retractor muscles occupied a greater proportion of the tail in taxa having relatively short tails (r=– 0.71, P < 0.00l and r=– 0.66, P = 0.001, respectively), and tail length dimorphism was more male‐biased in taxa in which body size dimorphism was more female‐biased (r=– 0.60, P < 0.001). These results support both the Morphological Constraint Hypotheses and the Female Reproductive Output Hypothesis. However, tests of other predictions, including those regarding patterns within N. sipedon, failed to support any of the three hypotheses. Comparisons among taxa suggest several species in which further tests of these hypotheses would be especially appropriate. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biological Journal of the Linnean Society Oxford University Press

Sexual dimorphism in snake tail length: sexual selection, natural selection, or morphological constraint?

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References (103)

Publisher
Oxford University Press
Copyright
Copyright © 1989 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0024-4066
eISSN
1095-8312
DOI
10.1111/j.1095-8312.1989.tb01570.x
Publisher site
See Article on Publisher Site

Abstract

Male snakes typically have longer tails relative to body length than females, but the extent of this dimorphism varies among species. Three hypotheses have been suggested to explain tail dimorphism. The Morphological Constraint Hypothesis proposes that males have relatively longer tails to accommodate hemipenes and retractor muscles. The Female Reproductive Output Hypothesis proposes that females have relatively shorter tails as a secondary result of natural selection for increased reproductive capacity. The Male Mating Ability Hypothesis proposes that sexual selection favours relatively longer tails in males during courtship. These hypotheses make different predictions about the relationships among tail length, body size, male reproductive morphology, female reproductive output, mode of reproduction, and male mating behaviour among and within taxa. Predictions were tested using published data for 56 genera in the family Colubridae and original data for the water snake, Nerodia sipedon. Tail length dimorphism was more male‐biased in tam having relatively short tails (r=–0.52, P < 0.001), hemipenes and retractor muscles occupied a greater proportion of the tail in taxa having relatively short tails (r=– 0.71, P < 0.00l and r=– 0.66, P = 0.001, respectively), and tail length dimorphism was more male‐biased in taxa in which body size dimorphism was more female‐biased (r=– 0.60, P < 0.001). These results support both the Morphological Constraint Hypotheses and the Female Reproductive Output Hypothesis. However, tests of other predictions, including those regarding patterns within N. sipedon, failed to support any of the three hypotheses. Comparisons among taxa suggest several species in which further tests of these hypotheses would be especially appropriate.

Journal

Biological Journal of the Linnean SocietyOxford University Press

Published: Oct 1, 1989

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