Does a sap feeding marsupial choose trees with specific chemical characteristics?

Abstract

Only about 20 vertebrate species are known to feed regularly on tree sap. One of these is the yellow-bellied glider (Petaurus australis), a marsupial that obtains between 16% and 80% of its diet from eucalypt sap. We reviewed the literature on sap feeding by the yellow-bellied glider and identified 10 species from which it most frequently obtains sap. These species come mainly from a few sections of the subgenus Symphyomyrtus, which accounts for two-thirds of over 2000 sap trees reported, but more specifically sections Latoangulatae and Maidenii within this subgenus. Some of these key species contain relatively high concentrations of foliar nutrients and each is an important food tree for at least one of the arboreal folivores - koala (Phascolarctos cinereus), greater glider (Petauroides volans), and common ringtail (Pseudocheirus peregrinus) and brushtail possums (Trichosurus vulpecula). Because yellow-bellied gliders, like the arboreal folivores, prefer to feed from certain individuals within a species, we hypothesized that these trees possess a unique chemical signature that links sap-feeding with the concentrations of available nitrogen and formylated phloroglucinol compounds in leaves - the nutritive and defensive chemicals that influence feeding on these species by marsupial folivores. We tested this hypothesis in samples of leaves and bark collected from E. punctata and E. viminalis but found no link between chemistry and sap feeding and conclude that other aspects of an individual tree, such as sap flow or sap chemistry, determine whether gliders will target it for sap.