Effects of forest edges on herbivory in a New Zealand mistletoe, Alepis flavida

This study examined how forest edges influenced leaf and floral herbivory, as well as seed predation, in a native New Zealand mistletoe species, Alepis flavida. Plants growing on forest edges and in forest interior were compared, and effects of plant size and the neighbouring conspecific plant community were also examined. Leaf herbivory by possums was significantly greater on forest edges than in forest interior in a year of high possum damage, but not in a year with low damage levels. Insect leaf herbivory did not differ between forest edges and interior. Although equal numbers of plants on edges v. interior experienced some floral damage by a specialist caterpillar, there were significantly higher levels of damage on plants growing in the forest interior than on forest edges. Plants with floral damage were larger than plants without damage, and distance to neighbouring mistletoe plants was positively correlated with amount of floral damage, but only for plants in the interior. Significantly greater numbers of plants on edges than in the interior exhibited seed predation by the same specialist caterpillar that caused floral damage, suggesting greater fruit abortion rates in the interior. Amounts of seed damage were inversely correlated with plant size. Forest edges had much stronger effects on leaf herbivory by possums, as well as floral herbivory and seed predation, than did plant size or the neighbouring plant community.