Life on the phylloplane: Eocene epiphyllous fungi from Pikopiko Fossil Forest, Southland, New Zealand

Abstract

Leaf surfaces provide a habitat for a wide range of organisms including bacteria, fungi, algae and bryophytes. Because the leaves of subtropical and tropical rainforest trees are mainly evergreen, these allow a longer time for foliicolous organisms to colonise and complete their life cycles, and evidence of these organisms can sometimes be found on fossil leaves. Here we describe a highly diverse group of epiphyllous fungi assigned to at least 10 genera and 15 morphotypes that have been isolated from late Eocene (c. 35 Ma) leaves preserved as carbonaceous compressions associated with the in situ Pikopiko Fossil Forest, western Southland. The fungi are described and illustrated, a new genus and species is established: Dennisiellinites pikopikoensis gen. et sp. nov; and the epiphyllous genera recorded from Australian Late Cretaceous and Cenozoic fossil leaves are listed for comparison. The Pikopiko fungi were found most commonly on the upper surface of angiosperm leaves and their abundance in the palaeo-rainforest suggests that climatic conditions in southern South Island during the late Eocene at a palaeolatitude of c. 54°S were subtropical, ever-wet and humid. This is the first time that a diverse range of epiphyllous fungal genera have been described from fossil leaf cuticle in New Zealand.