Distribution and population structure of the loranthaceous mistletoes Alepis flavida, Peraxilla colensoi, and Peraxilla tetrapetala within two New Zealand Nothofagus forests

Abstract

Our results confirm the findings of an earlier study that suggested niche partitioning in the way Alepis flavida and Peraxilla tetrapetala utilise the available resources within the Nothofagus solandri canopy; Alepis flavida is almost exclusively an outer branch parasite while Peraxilla tetrapetala occurs most often on inner branches and the host trunk. Peraxilla colensoi has a similar distribution within host trees to Peraxilla tetrapetala, except that it parasitises Nothofagus menziesii. All three mistletoes showed non-random distribution patterns in terms of the host trees they parasitise, being found more often on larger trees. Larger host trees also carry a greater volume of mistletoe than do smaller host trees. For Alepis flavida and Peraxilla tetrapetala we found no evidence of host exclusion, whereby the presence of one mistletoe excludes the other mistletoe species establishing, observing the converse where host trees were more likely to have both mistletoe species present than expected. Peraxilla colensoi was found to be more common in Nothofagus-podocarp forest than in Nothofagus or Nothofagus-Weinmannia-Metrosideros forest. Alepis flavida and Peraxilla tetrapetala population structures suggest that recruitment of young mistletoe plants has been relatively continuous over the past few years in the Nothofagus solandri forest we studied while the Peraxilla colensoi population structure showed an apparent absence of small plants suggesting a lack of recruitment in the Nothofagus menziesii forest we studied.

Keywords:

• Alepis flavida
• Peraxilla colensoi
• Peraxilla tetrapetala
• Loranthaceae
• mistletoes
• population structure
• parasitism
• ecology
• conservation
• Nothofagus menziesii
• Nothofagus solandri