Myrmecochorous plants in Australia and their dispersal by ants

Abstract

Field experinfents and observations indicate that c. 1500 species, representing 87 genera and 24 families, of Australian vascular plants are myrmecochorous, i.e. regularly dispersed by ants because of ant-attracting structures (elaiosomes) on their seeds or fruits. Ant behaviour towards an elaiosome depends primarily upon the species of ant but also upon the individual ant and the field situation. Australian myrmecochorous plants are unexpectedly numerous and strikingly different from those known from the northern hemisphere. Most of them are shrubs. Diplochory is common. Subsidiary myrmecochorous features are rare. The elaiosomes are often firm and persistent. Australian myrmecochorous plants are not forest mesophytes, as are most of those previously known, but xerophytes of the Australian dry heath and sclerophyll vegetation. Apparently myrmecochory was not brought to Australia with immigrating plants, but developed within Australia, probably under the selective influence of xeric habitats as they spread during the Tertiary.