The mistletoe flora of southern Western Australia, with a particular reference to host relationships and fire

Abstract

The mistletoe flora of southern Western Australia was studied over a 30-year period with a particular emphasis on distributions, host relationships and fire. The study area encompassed Western Australia south of ~26° S. It included all the South-west Botanical Province and southern components of the Eremaean Botanical Province, with the northern boundary corresponding with bioregional boundaries. Vegetation ranges from wet and dry sclerophyll forest through woodlands and heaths to deserts. The mistletoe flora comprises 21 taxa, 19 in the Loranthaceae and two in the Santalaceae. They infect 153 species in 25 genera and 15 families. The Fabaceae provides hosts to more taxa than any other family; however, the genus with most host species, Eucalyptus (Myrtaceae), supports only two mistletoe species, one of which barely enters the study area. Melaleuca (also Myrtaceae) is host to seven species. The number of mistletoe species per bioregion ranges from 0 to 18, with 12 species in the seven bioregions of the South-west Botanical Province and 20 in the six bioregions of Eremaean Botanical Province that are within the study area. In both provinces, diversity is lower in coastal areas and higher in more arid, inland areas. Most mistletoe habitats in the study area are fire-prone. One species is probably capable of resprouting whereas all other taxa are obligate seeders. With no means of in situ seed storage, post-fire recovery depends on seed importation. Fire is the most pervasive (but not the only) threatening process operating today. However, fire management in more populous agricultural and urban areas safeguards many populations in the South-west Province.