The relationship between limb reduction, body elongation and geographical range in lizards (Lerista, Scincidae)

Aim: The relationship between changes in body form (limb reduction and body elongation) and geographical range size was investigated across 68 species of Lerista, a species-rich clade of Australian scincid lizards that exhibits extensive interspecific variability in both body form and range size. Location: Lerista occurs across the entire Australian mainland, with diversity concentrated in arid and semi-arid regions. Methods: Geographical range size was estimated directly from c. 14,000 museum specimens using bioclimatic modelling in MaxEnt. Body form was quantified using principal components analysis of morphometric variables. Comparative analyses testing for a correlation between these two variables used a full Bayesian approach that accounts for uncertainties in trait optimization as well as in tree topology and branch lengths. Results: A serpentine body form (elongated with reduced limbs) was significantly associated with smaller geographical range size, in both phylogenetically corrected and uncorrected analyses - but only if species from single localities (whose ranges could not be modelled using the above methods) were excluded. Main conclusions: These results suggest a general predictive relationship between body form and geographical range size in lizards: elongate, limb-reduced lizards tend to exhibit more restricted geographical ranges that may reflect reduced dispersal ability and may also predispose them to greater vulnerability of extinction.