Generalist mistletoes and their hosts and potential hosts in an urban area in southwest China

Abstract

The generalist mistletoes, Taxillus nigrans (Hance) Danser and Scurrula parasitica L., are widely distributed in southwest China. To reveal what tree species were parasitized and the relative extent of parasitism on different host tree species, we investigated all the trees and shrubs—5343 individuals of 85 species from 42 families—in a 55.4-ha area within Sichuan University’s Wangjiang Campus in Chengdu, southwest China. We found that mistletoes parasitized 991 individual trees and shrubs of 41 species from 26 families, which accounted for 25.9% of the 3832 individuals of the 41 host species. Among the host species, 35 were native to China and six were non-native species. Four host tree species with the highest parasitism prevalence—Platanus acerifolia (84.8%), Robinia pseudoacacia (64.8%), Metasequoia glyptostroboides (45.5%), and Broussonetia papyrifera (41.7%)—accounted for 51.8% of all parasitized host individuals. Among all the 85 non-host and host species, species with larger sizes (≥20) were significantly more likely to be host species than species with smaller sample sizes (<20). Within host species, parasitized individuals were significantly larger than non-parasitized individuals both in height and DBH. Parasitic intensity showed a significant positive correlation with host height and DBH. Branches with a basal diameter less than 5 cm had 71.1% of the mistletoe clumps. There was a significant positive correlation between mistletoe clump length and host height and DBH. The lengths of mistletoe clumps on the outer position of the branches were significantly longer than the lengths of mistletoe clumps on the intermediate or inner positions of the branches.