Mistletoes on mistletoes: The floral ecology of Amyema miraculosum and its host, Amyema miquelii (Loranthaceae)

Abstract

In Victoria, self-incompatible Amyema miraculosum may exist as a locally obligate parasite on partially self-compatible Amyema miquelii. For the first time, the pollination ecology of a mistletoe on a mistletoe is analysed. Both species were generalist ornithophiles with overlapping flowering seasons from January to March. Consequently, the hyperparasite was in competition with its congeneric host for pollen vectors belonging to the local nectar bird guild (Meliphagidae and Zosteropidae). Amyema miquelii produced flowers that were longer-lived, and had a higher nectar content, than those of A. miraculosum. From mid February through March, A. miquelii plants offered more inflorescences, with open flowers, than A. miraculosum. There was an average of twice as many flowers on an A. miquelii inflorescence as on an A. miraculosum inflorescence, Not surprisingly, more than 70% of avian foraging bouts observed were to A. miquelii only. Eight bird species foraged for nectar on A. miquelii while only five were recorded on A. miraculosum. While 22% of all foraging bouts were interspecific, no examples of interspecific hybridization were found. This corresponds with previous observation of the reciprocal failure of interspecific crosses in vitro.