Evol Ecol Res 1: 303-316 (1999) Full PDF if your library subscribes.
Natural selection on hatchling body size and mass in two environments in the common lizard (Lacerta vivipara)
and Jean Clobert
Laboratoire d’Ecologie, CNRS UMR 7625, Université Pierre et Marie Curie, Bât. A, 7ème étage, 7 quai St. Bernard, case 237, F-75252 Paris Cedex 05, France
Author to whom all correspondence should be addressed.
Differences in life-history traits among populations living in different environments can arise as adaptations to different selective regimes present in these environments. In this study, we investigated patterns of natural selection on body size (snout-vent length and tail length) and mass in hatchlings of the common lizard (Lacerta vivipara) raised in two different environments, where the local populations of L. vivipara have different life-history traits. To investigate patterns of natural selection, we raised hatchlings from one high-altitude population in outdoor enclosures located at high and low altitude and we recaptured them before they entered hibernation. We found significant directional selection for higher hatchling body mass and tail length at both sites, whereas hatchling snout-vent length was not correlated with survival. Stabilizing selection gradients were not significant for any of the traits considered at both sites. Differential hatchling mortality may directly affect maternal investment in litter size. In this case, the proper focus of selection might be on mothers. We checked this issue by estimating: (1) the trade-off between litter size and hatchling size and mass; and (2) the correlation between litter size and the proportion of living offspring per litter. Although litter size was negatively associated with hatchling size and mass, we did not find any correlation between fecundity and offspring survival. In conclusion, we found no differences in the patterns of selection between the two environments. These findings are in agreement with previous results showing that differences in life-history traits between these high- and low-altitude populations may arise from plastic responses to proximate cues, rather than genetic adaptation to different selection pressures.
Keywords: body mass, body size, environment, Lacerta vivipara, natural selection, survival.
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