Limb Loss in the Genus Scelotes

Elyse Freitas – Research Statement:

With more than 1600 species, the lizard Family Scincidae is the most biodiverse group of lizards. The family has a cosmopolitan distribution and is found on every continent except Antarctica and on numerous oceanic islands. Consequently, Scincidae is ecologically and morphologically diverse and is a good system for studying the evolution and distribution of body form in lizards.

One of the most interesting trends within lizards is the reduction and loss of limbs and the evolution of an elongate snake-like body form, possibly in response to the evolution of a grass-swimming or burrowing lifestyle. Within Scincidae, limb reduction or the complete loss of limbs has evolved more than twenty-five times independently. However, the evolution of limblessness is not well understood. The scincid genus Scelotes is one of only four skink genera that have both limb-reduced and limbless members. Therefore, understanding the pattern of limb loss in Scelotes in concert with the genus’ distribution and biogeography can help elucidate patterns of limb loss within skinks and, more broadly, within lizards as a whole.

The genus Scelotes comprises 21 species of limb-reduced and limbless semi-fossorial scincid lizards from sub-Saharan Africa, with 20 of these species found in the southern African subcontinent (mainly Namibia, South Africa, Swaziland, Lesotho, and Mozambique). Species inhabit narrow ranges predominately distributed throughout coastal areas of the subcontinent, although several ranges extend into inland sandy habitats, and limbed and limbless forms are found in neighboring localities. Despite the evolutionary implications of its distribution and patterns of limb loss, little is known about the relationships of species within genus. Understanding the systematics of Scelotes through phylogenetic reconstruction will allow us to reconstruct ancestral states and elucidate patterns of limb loss within the genus.