Evolution and ecology of developmental processes and of the resulting morphology: directional asymmetry in hindlimbs of Agamidae and Lacertidae (Reptilia : Lacertilia)

In this paper, the evolution and ecology of directional asymmetry (DA) duri ng the developmental trajectory (DT) is compared with that of its product, morphological DA (MDA). DT and MDA are calculated for two bilateral morphol ogical scale characters of lizards, the number of subdigital lamellae benea th the fourth toe in 10 agamid and 28 lacertid taxa, and the number of rows of ventral scales in 12 lacertid taxa. MDA, the subtraction between left a nd right sides (classical measure of DA), is functional in adult animals. R esults confirm the hypothesis that, in DT, the repression parameters a (con stant) and b (repression slope) of counts on the right side with those on t he left describe a developmental process. No phylogenetic or environmental effects were observed on a and b, but analyses considering both a and b tog ether show non-random phyletic patterns. Independent analyses deduced the s ame ancestral DT in Agamidae and Lacertidae. In Lacertidae, distance betwee n pairs of taxa in a+b (standardized values) correlates positively with the phylogenetic distance between taxa. Phyletic trends in MDA are indirect, a nd due to the link of MDA with a+b. The MDA of species is more dissimilar i n sympatry than in allopatry. The phyletic trends suggest evolution of DT, while the association of MDA with sympatry suggests that ecological pressur es shape MDA in adult animals. Evolution of DT is independent from that of its product, MDA-adaptive determinism defines the result of, but not the me chanistic process of, development. Deterministic environmental processes de fine MDA, and deterministic evolutionary processes define the interactive r esult of a and b, but not each separately. According to circumstances, diff erent DTs produce similar or different MDA, and a particular DT can produce different MDAs. (C) 2000 The Linnean Society of London.