Evolutionary consequences of eating: Trichosurus vulpecula (marsupialia) and the genus Eucalyptus

Abstract

While being somewhat specialized on a diet of mature Eucalyptus leaves (66% of feeding time), wild Trichosurus vulpecula consume an average of three different foods per night. Usually, these foods are two different species of Eucalyptus leaves, and “ground feeding.” Laboratory feeding experiments indicate that this ingestion of a variety of foods is due to severe limitations on the quantity of Eucalyptus leaves a possum is capable of consuming. It is argued that the limitation is due to plant toxins (volatile oils, phenols) present in Eucalyptus leaves, rather than to “normal” nutritional factors. We hypothesize that Eucalyptus toxins indirectly regulate possum populations at levels that afford the Eucalyptus trees some degree of protection from possum predation. In addition, we suggest that the “New Zealand phenomenon” can be explained by a lack, and acquisition, of plant chemical defenses against herbivores introduced from chemically more complex environments.