Host species of mistletoes (Loranthaceae and Viscaceae) in Australia

Abstract

In order to study the relationships between mistletoes and their host species, comprehensive collections of both mistletoes and hosts are needed. The effect of sampling effort on the estimation of mistletoe host range was demonstrated in a comparison of an inventory of host mistletoe interactions published by Downey in 1998 and a 2019 inventory presented here, which is based on data from collections in the Australian Virtual Herbarium and information in the literature. New hosts were recorded for 93% of the 90 Australian mistletoes. There were 338 previously known hosts recorded to be parasitised by additional mistletoe species, and 317 new host species that were not previously known as mistletoe hosts (25 being alien species). These were from 78 new host genera and 13 new host families. The total number of host species was 1186 within 327 genera from 92 host families. A total of 63% of all Australian mistletoes parasitise species of either Eucalyptus or Acacia or both these genera. The large rise in host species recorded in less than two decades between inventories suggests that current knowledge of hosts is still incomplete, such that further new hosts will be discovered in future. Some mistletoe species show a strong preference to one host family or genus but due to insufficient collecting it is premature to conclude that any of the three species known from a single host are host specific.

Parasites on parasites: hyper‐, epi‐, and autoparasitism among flowering plants

“…Therefore, mistletoes with epicortical roots could be expected to engage in epiparasitic relations more often than species forming solitary haustorial morphotypes. Nevertheless, based on the extensive lists of epiparasitic relations among mistletoes generated by Wilson and Calvin (2017) and Clark et al (2020), species bearing epicortical roots do not appear to be involved in epiparasitic relations more than species with other haustorial types.…”

“…On the other hand, Santalaceae encompasses the largest number of obligate epiparasites, including Dendrophthora epiviscum (Griseb.) Eichler, approximately 10 species of Phoradendron (Wiens, 2002; Kuijt, 2003), and at least 10 other species of Viscum from Australia, Asia, and Africa (Pundir, 1981; Glatzel and Balasubramaniam, 1987; Downey, 1998; Polhill and Wiens, 1998; Sardesai et al, 2019; Clark et al, 2020).…”

“…Nevertheless, little is known about the structure and physiology of Krameriaceae species, as few representatives of the family have been investigated (Brokamp et al, 2012). Considering mistletoes, the occurrence of facultative epiparasitism has been reported for a wide diversity of species belonging to Santalaceae and Loranthaceae (Wilson and Calvin, 2017;Clark et al, 2020). The latter represents the most speciose mistletoe clade, encompassing about 950 species and four distinct haustorial morphotypes (Kuijt, 2015;Teixeira-Costa et al, 2020).…”

“…Thus, we consider that the presence of fully formed and functional haustoria is a prerequisite for all instances of hyperparasitism in flowering plants. The following sections summarize and discuss in detail the empirical knowledge on hyperparasitic plant interactions, providing a compilation of known hyperparasitism cases with our novel findings (see Supporting Information) following the recent comprehensive reports on mistletoe epiparasitism by Wilson and Calvin (2017) and Clark et al (2020).…”

Untitled

“…Erianthemum dregei is a parasitic shrub belonging to Loranthaceae family. It is widely distributed in the northern part of KwaZulu-Natal, South Africa 21 . E. dregei has been used in treatments of sexually transmitted diseases, snake-bites and stomach ailments 22 .…”