A common woodland lichen of eastern Australia that has been recorded only twice from New Zealand in 1934 and 1976, and then only from the far north of the North Island has turned up on the Chatham Islands. The lichen, Heterodea muelleri is a leafy species that in Australia grows in moderately open woodland habitats. In New Zealand, until it was recognised from the Chatham Islands it had only ever been recorded from dune slacks somewhere on the Ninety Mile Beach and from damp sandstone ridges in light scrub near Puheke, Karikari Peninsula.
The Chatham gatherings came from the north-western end of Ocean Bay, Chatham Island and from the top of Hakepa Hill (Walkemup), Pitt Island. At Ocean Bay the lichen grew on sandy peat and clay above schist on the margin of salt and wind blasted vegetation. In this habitat it was associated with the lichens Cladia aggregata and C. retipora, and sedge Lepidosperma australe. On Hakepa Hill specimens were gathered from amongst the dense drifts of Cladonia lichens that grow between the low, windswept fernland that covers most of that trachyte peaks summit.
New Zealand's foremost lichenologist Dr David Galloway is delighted with the finds, which were identified from gatherings made by New Zealand botanists Dr Peter J. de Lange and Dr Peter B. Heenan as part of their study of the vegetation of the Chatham Islands. Previously, Dr Galloway had undertaken three "fruitless" searches of the far north of New Zealand, the last undertaken with one of the world's Cladonia lichen authorities Dr Sam Hammer of Boston University, U.S.A. Both men were keen to see if the species still survived in New Zealand. However, they found that much of the likely habitat on the Karikari Peninsula had been converted to farmland and holiday homes, while that available on the Ninety Mile beach had been planted over in pines.
The presence of Heterodea on the Chathams adds to a small group of plants (Atriplex australasica, Kurzia dendroides and Leucopogon parviflorus) now known to be shared between the islands and Australia.