Loranthaceae

Positive effects of fragmentation on plant reproduction are uncommon; in a literature review we found significant negative effects on fruit or seed set for 50 plant species, compared to 26 species showing no effect, and only nine affected positively. One of these is the declining New Zealand mistletoe Peraxilla tetrapetala (Loranthaceae), and here we investigate the mechanism of this positive effect. P. tetrapetala requires visits from native bird or bee pollinators to produce fruit.

The Australian brushtail possum (Trichosurus vulpecula) has been blamed for the decline of three native New Zealand beech mistletoe species (Alepis flavida, Peraxilla tetrapetala and Peraxilla colensoi, Loranthaceae), but there are few quantitative data on possum effects, and anecdotal evidence is often conflicting. We present results from two monitoring programmes that suggest possum control operations can improve mistletoe health.

This study provides the first quantitative comparison of methods for monitoring herbivory and growth of New Zealand beech mistletoes (Alepis flavida, Peraxilla colensoi and Peraxilla tetrapetala). Four monitoring methods-leaf maps, volume estimates visual estimates of browse and foliage density, and rePeat fixed-point photographs-were used to assess the health of 60 permanently tagged mistletoe plants in four South Island beech forests between February 1997 and February 1998.

Recent work at several central South Island sites has shown that the bird-pollinated mistletoe Peraxilla tetrapetala (Loranthaceae) is extensively pollen-limited. We studied the diet, time-budget, and densities of its principal pollinator, bellbirds (Anthornis melanura, Meliphagidae), at Craigieburn to find out what aspect of bellbird ecology may be limiting pollination.

Flower predators (florivores) may affect plant reproduction directly through loss of pollen and ovules, or indirectly by deterring pollinators which avoid damaged flowers. Caterpillars of the widespread endemic moth Zelleria maculata feed inside flower buds of the endemic mistletoes Peraxilla tetrapetala and P. colensoi in New Zealand. We measured flower predation rates between 1995 and 2007 at 24 sites throughout New Zealand and assessed Zelleria feeding impact on fruit set.