ISSN:
1442-9993
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Vertebrate herbivores generally have greater effects than invertebrates on plants. However, few studies have investigated the effects of both invertebrate and vertebrate herbivores on a single plant species. In New Zealand, nationwide declines in mistletoe populations have often been attributed to possum herbivory, but never to insect herbivory. The main goal of the present study was to document levels of vertebrate and invertebrate herbivory on endemic New Zealand mistletoe plants to suggest whether herbivory is leading to mistletoe decline. In the present study, the annual amount of leaf loss from herbivory by the brushtail possum (Trichosurus vulpecula), insect herbivory and leaf abscission were measured in two populations each of three mistletoe species (Alepis flavida, Peraxilla colensoi, and Peraxilla tetrapetala, Loranthaceae). In two populations of each species from February 1997 to February 1998, abscission accounted for the most leaf loss (range 10–84% of total mean leaf area, mean 33%), whereas insects and possums usually removed small and similar amounts (less than 3%). Possum browse caused large amounts of abscission in only one population (A. flavida at Eglinton). Observed possum browse was more heterogeneous than insect browse among branches within a plant (possum coefficient of variation = 2.63, insect CV = 1.98, P 〈 0.001), among plants in a population (possum CV = 2.15, insect CV = 0.69, P 〈 0.001), and between populations (possum CV = 1.36, insect CV = 1.09). Moreover, insects damaged 100% of the study plants but never removed more than 16% of leaf area on a single plant, whereas possums only browsed 32% of the study plants but severely defoliated some plants. Thus, while the mean amount of biomass removed across a population may have important consequences for mistletoe survival, the effect of possums on mistletoe populations may also depend on the heterogeneity of browse among individuals in the population.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1442-9993.2001.01129.x
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