Mistletoe (Amyema miquelii and A. pendulum) seedling establishment in eucalypt hosts in eastern Australia.
Abstract
Germination and early seedling development were compared in two mistletoe species that parasitize and sometimes kill their eucalypt hosts. Germination in cohorts inoculated in host branches at different times of the year was 77-100% and 95-100% for Amyema miquelii and A. pendulum, and A. miquelii seeds varied significantly between cohorts. Mistletoe seedlings of both species inoculated on dead branches survived for a maximum free-living period of 5 months. Accordingly, establishment was measured 6 months after inoculation and was 13-53% and 0-60% among A. miquelii and A. pendulum cohorts, respectively. A. miquelii seedlings inoculated in November and December 1990 experienced higher mortality during the first 2 months than those inoculated in other months. Desiccation appeared to be a major cause of high summer mortality. In most cohorts, post-dispersal predation by rosellea parrots (Platycerus spp.) was a major cause of early seedling mortality. Predation varied between 3 and 100% among cohorts, and averaged 23% for A. miquelii and 85% for A. pendulum. The low establishment of A. pendulum cohorts was primarily due to seedling predation. Both mistletoe species were inoculated on usual hosts with the exception of A. pendulum on Eucalyptus blakelyi. Surprisingly, establishment of A. pendulum seedlings after 6 months did not differ significantly between E. blakelyi and E. bridgesiana (a usual host). The rarity of natural occurrences of A. pendulum on E. blakelyi appears to be due to post-seedling incompatibility between mistletoe and host. A. miquelii seedling establishment on E. blakelyi and E. melliodora hosts did not vary significantly with branch diameter (range 3-40 mm) in three out of four host-cohort combinations. However, maximum establishment tended to occur on intermediate-sized branches (70-20 mm diameter).