Portal de Periódicos da CAPES

Patterns of Covariation in Life History Traits of Squamate Reptiles: The Effects of Size and Phylogeny Reconsidered

1985; University of Chicago Press; Volume: 126; Issue: 2 Linguagem: Inglês

10.1086/284411

1537-5323

Arthur E. Dunham, Donald B. Miles,

Animal Behavior and Reproduction

Stearns' (1984) major conclusion was that patterns of covariation in life history traits within squamate reptiles are strongly influenced by classwide correlations with female body length. This result minimizes the importance of microevolutionary processes, such as adaptation to local environmental conditions, in shaping life history variation. Microevolution would, in effect, be constrained by ancestry or lineage, which limits the magnitude and direction of covariation in life history variables. On the basis of a corrected and expanded data base, we present evidence that argues against strong phylogenetic constraint at the ordinal level on the patterns of covariation in life history traits among squamate reptiles. Rather, our finding of significant effects of family-level taxonomy on four life history variables (clutch size, mode of reproduction, brood frequency, and age at maturity), with the effects of size removed, suggests that tests of historical hypotheses within the squamates should be limited to comparisons at the family level, or below (Lauder 1982). After the removal of correlations with female body length, we found significant residual variation at the order, family, and genus levels for clutch size and age at maturity in direct opposition to Stearns' major conclusion. Furthermore, the within-family patterns of covariation revealed by our analysis suggest that local adaptation, plasticity of response to local environmental heterogeneity, and physiological constraints (e.g., the strong correlation of the mode of reproduction with brood frequency) are likely to be important determinants of life history variation. Although Stearns' (1984) analyses were weakened by errors in the data, his approach to the study of life history variation represents a significant advance. Although we differ with respect to the appropriate taxonomic level useful in making comparisons in patterns of life history variation in reptiles, our results are similar to Stearns' in demonstrating that phylogenetic effects cannot be ignored in analyses of the evolution of life history traits.