Egg shape and size allometry in geckos (Squamata: Gekkota), lizards with
contrasting eggshell structure: why lay spherical eggs?
L. Kratochvı´l1 and D. Frynta2
Abstract
Hard, highly calcified eggshells evolved several independent times during the
history of amniotes. Because of phylogenetic conservatism of this
trait, lineages in which closely related taxa differ in eggshell structure are
rare. Four gekkotan families (Carphodactylidae, Diplodactylidae,
Eublepharidae and Pygopodidae) have eggs with soft shells, while their close
relatives (Gekkonidae) lay eggs with hard shells. Geckos thus
offer a rare opportunity to compare the impact of the emergence of a hard
eggshell on the economy of egg architecture. Because a sphere has
the smallest surface area of all three-dimensional solids of a given volume,
spherical eggs in geckos with hard eggshells reduce calcium
investment and should therefore be advantageous. Here, we document that
hard-shelled gekkonid eggs are indeed more spherical than those of
the other gecko lineages. However, within gekkonids, small species lay more
elongated eggs than larger species. We speculate that miniature
gekkonid females, which lay larger