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Ecological Morphology and Life History Variation
During last decades, lizards were among the model animal groups for studying factors which determine the variation of life-history and demography traits within and among species. These studies have developed an advanced theoretical and methodological framework, but the weak point is that they cover only a small set of populations and taxa. The problem is that both mark-recapture and experimental studies - the main tool to obtain data on growth and longevity in wild animals - are very time-consuming.
A promising alternative tool to get such data is the recording structures analysis (Mina & Klevezal, 1970; Klevezal, 1988), also known as skeletochronology (Castanet et al. 1977). This method based on counting and measuring growth layers in bone or other hard tissues provides not only an accurate age determination in reptiles and amphibians, but also a quantitative estimation of the pattern of bone growth (Smirina, 1969, 1994; Castanet, 1970, 1994; Castanet & Smirina, 1990). Moreover, individual trajectories of body growth can be back-calculated from the bone growth marks (Smirina, 1983; Marunouchi et al., 2000, etc.).
In cooperation with E. M. Smirina (N. K. Koltsov Institute of Developmental Biology, research team of G. A. Klevezal) I have studied altitudinal variation and sex differences for age structure, asymptotic body size and growth pattern in two related lizard species (Lacerta agilis boemica and L. strigata) from the Caucasus. The data were obtained from preserved specimens, using skeletochronology and back-calculation methods. As nobody before had applied the back-calculation technique to squamate reptiles, methodological problems which can arise by inferences about body growth from skeletochronological data have been another important target of our study (Roitberg & Smirina, 1995, 2005, in press). An extension of this work is our current study on the geographic variation of sexual size dimorphism in a widespread lizard species, Lacerta agilis (Roitberg & Smirina, in review; Roitberg, 2005; Roitberg, in prep.). This study may have some methodological interest as it includes a meta-analysis and considers different statistical estimators of adult body size. Choice of appropriate estimators for this trait imposes problems for ectoterm animals as they exhibit substantial post-maturity growth.
Trends and Constraints in Morphological Variation
My previous research involved various aspects of intraspecific morphological variability in lacertid lizards. Reptilian pholidosis is an excellent model for studying general regularities in variation and evolution of morphological structures. This is particularly true for Lacertidae whose scutellation consists of well-defined series providing plenty of precisely countable characters. Although these characters are widely used in intraspecific taxonomy as well as in microevolutionary studies the morphological content of the variation usually remains out of special analysis. Studying variation of pholidotic traits in several species of the genera Lacerta and Darevskia, I addressed various topics like the intrinsic trends of variability due to developmental constraints (Roitberg, 1991, 1999b; Roitberg & Rostova, 1999 and in prep.), morphological aspects of speciation (Roitberg, 1999a), differences in the level of phenetic differentiation in related sympatric species (Roitberg, 1994).
Relevance to Climate Change
Both life history and morphological studies could contribute to the problem of the effect of the global warming on natural populations. Dynamics of microgeographic distribution of some lizard species during last decades ( Roitberg et al., 2000; Tuniev, 2003) as well as comparing life history (using skeletochronology) and external morphology of recent samples with those collected from the same localities some 20-50 years ago (cf. J. C. Lee, 1992) could provide very useful data.