Most New Zealand mistletoes of the family Loranthaceae have experienced a dramatic range contraction and local extinction in some areas. Ileostylus micranthus (Hook f.), is the only loranthaceous mistletoe, which is not regarded as threatened. Yet little is known about some basic ecological features of this species, such as gender, pollination mode, pollinators and spatial distribution in the landscape. The elucidation of these features is valuable to understanding the ecology and assessing the conservation status of Ileostylus.

I investigated therefore the breeding biology of two populations of Ileostylus micranthus on the Port Hills, Canterbury. Further a seed-sowing experiment was conducted comparing the establishment of Ileostylus in 12 different sites situated near Lyttelton Harbour, on the Porthills and within the city of Christchurch using two Ileostylus seed sources. Three different hosts were also tested for the establishment of Ileostylus.

The research revealed that the investigated populations were not dioecious, as has been observed in populations in other parts of New Zealand, but hermaphrodite, displaying significant differences in phenotypic gender between plants. Predation of sexual parts with up to 14% of damaged buds distorted the results of the gender assessment. Flower predation seemed to be confined mainly to the native specialist moths, Zelleria species and Tatosoma agrionata. Ileostylus was self-fertile and displayed a high rate of autonomy (23.2% for Lyttelton and 42.3% for Moncks Spur). Despite employing a range of pollination modes, such as cleistogamy, night and day insect pollination, and possibly wind pollination, Ileostylus may have suffered from pollen litnitation with low fruit set rates of 17.2% for Lyttelton and 35.5% for Moncks Spur. The frnit predation caused by Zelleria was at a rate of approximately 5%. Diurnal insect pollinators (mainly Diptera) and nocturnal insect pollinators (mainly Lepidoptera) appeared to play equal roles in the pollination of Ileostylus. The fiuit removal rate was high. The establishment rate was low with 10.8% and patchy. The conservation status "local", requiring monitoring, seems appropriate at the current level of knowledge. The next step of research should be an enquiry into the causes of pollen limitation and the patchy establishment in Ileostylus.