Host Specificity of Lysiana exocarpi subsp Exocarpi and Other Mistletoes in Southern South-Australia

Abstract

A study was conducted of host specificity of six mistletoe species in 17 sites in southern South Australia. The mistletoe Lysiana exocarpi occurred on eight of the 15 potential host species encountered in the survey but disproportionally parasitised Heterodendrum oleifolium and Myoporum platycarpum as its major hosts. More than 90% of L. exocarpi plants infested these two hosts. The other five mistletoe species, Amyema linophyllum, A. miquelii, A. miraculosum, A. preissii, and A. quandang, were highly host specific, occurring on only one host species or on species of closely related taxa.

Although L. exocarpi was found throughout the study area, its occurrence on M. platycarpum showed significant geographic variation. Myoporum platycarpum was heavily infested by L. exocarpi at sites with an annual rainfall of > 250 mm but not at sites with < 250 mm annual rainfall. At sites with less rainfall, M. platycarpum was infested by another mistletoe species, A. miraculosum. Across all sites, the proportion of M. platycarpum trees infested by L. exocarpi was significantly correlated with annual rainfall. No such trend was detected for H. oleifolium infested by L. exocarpi.