EVOLUTIONARY CORRELATES OF MICROPHAGY IN ALKALOID-CONTAINING FROGS (AMPHIBIA, ANURA)

Frogs of the genus Mantella (Ranidae) are characterized by several der ived characters, among them microphagy and presence of skin alkaloids. A comparison with other alkaloid-containing frogs (belonging to the D endrobatidae, Myobatrachidae and Bufonidae) showed that, beside the al kaloids, these share several of the apomorphies typical for Mantella. Since most of the derived characters can be explained by microphagous and myrmecophagous specialization, we postulate the existence of an ev olutionary etho-morphological character complex involving microphagy, alkaloid accumulation from ant prey, aposematic colouration, diurnal a ctivity, modification of prey catching behaviour, modification of tong ue shape, reduction of teeth, and modification of several osteological skull characters related with the jaw opening mechanism. The existenc e of such a complex reduces the value of skin alkaloids and aposematic colouration for the assessment of phylogenetic relationships between Mantella and dendrobatids, so that a sister group relationship of thes e groups is unlikely. We present a flow diagram which gives a possible explanation of a convergent loss of strong mating amplexus and evolut ion of complex mating behaviour in both groups. Further we discuss the status of the small-sized dendrobatid genus Minyobates, whose charact eristic alkaloid profile and small size may be correlated with feeding specialization on mites; and we conclude that data support the hypoth esis of a small-sized microphagous ancestor of the bufonid clade.