HISTORICAL CHANGES IN THE ECOLOGY AND BEHAVIOR OF SEMAPHORE GECKOS (PRISTURUS, GEKKONIDAE) AND THEIR RELATIVES

Semaphore geckos (Pristurus) and their relatives have a very robust and explicit morphological phylogeny, consisting of a long pectinate tree in which the number of derived morphological states increases steadily through time. This clade consequently provides a firm base for investigating changes in ecology and behaviour. Data on these topics including diet, pattern of tail shedding and clutch size were integrated with the phylogeny and substantial regularity demonstrated in the way they have changed over time. Ancestral forms were apparently climbers on rocky surfaces and active in subdued light. There was subsequent shift into more open, sunny situations with two or three transfers into arboreal habitats which were accompanied by reversion to more shaded conditions, A change to ground-dwelling occurred perhaps twice within Pristurus, including the ancestor of the Spatalura clade, a group which has reverted to typical gecko nocturnality while still retaining diurnal activity. Overall, there has been a progression into hotter, drier and more open habitats. Other shifts within the clade are adoption of passive foraging techniques, development and elaboration of intraspecific tail signalling and change in the kinds of refuges used. Clutch size fell from two eggs to one early in the clade history with subsequent partial reversion to two. Ants and sometimes termites became an important item of diet in some taxa and frequent trombiculid mite infestation appeared in the terminal group within which caudal autotomy became confined to the tail base. Overall, the habitats occupied by morphologically advanced Pristurus appear more demanding, and perhaps less rewarding, than those in which their more primitive relatives live. This may result from species that did less well in competition, following each of the speciation events on the main stem of the phylogeny, being displaced into increasingly severe niches. The substantial morphological changes taking place in the evolution of the clade may be related to the problems of survival in these,