Evolution of viviparity in cold-climate lizards: testing the maternal manipulation hypothesis |
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Authors: | Hong Li Yan-Fu Qu Rui-Bin Hu Xiang Ji |
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Institution: | (1) Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu, 210046, China;(2) Hangzhou Key Laboratory for Animal Sciences and Technology, School of Life Sciences, Hangzhou Normal University, Hangzhou, Zhejiang, 310036, China; |
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Abstract: | We used a cold-climate viviparous lacertid lizard (Eremias prezwalskii) as a model system to test the maternal manipulation hypothesis. Twenty-four gravid females collected from a population in
Inner Mongolia (northern China) were maintained in the laboratory for the whole gestation length, with 12 allowed to bask
for 14-h daily and the other 12 for 10-h daily. Females selected lower body temperatures but did not thermoregulate more precisely
when gravid. The mean gestation length was shorter in females provided with longer basking opportunity. Neonates in the two
treatments differed in tail length and the number of ventral scales but not in other examined morphological traits, with offspring
born in the 14-h treatment having longer tails but fewer ventral scales. Offspring were sexually dimorphic at birth, with
females being smaller in tail length, head length and fore-limb length but having more ventral scales than males of the same
size. Offspring born in the 14-h treatment were not only faster runners but also grew faster than did offspring born in the
10-h treatment. Our data validate the main predictions of the maternal manipulation hypothesis that females should shift selected
body temperatures during gestation to provide optimal thermal conditions for developing embryos and that phenotypic traits
determined by maternal thermoregulation should enhance offspring fitness. Our study is the first to demonstrate that the maternal
manipulation hypothesis applies to cold-climate viviparous reptiles. |
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