Fruit characteristics of invasive bitou bush, Chrysanthemoides monilifera (Asteraceae), and a comparison with co-occurring native plant species

Abstract

Bitou bush, Chrysanthemoides monilifera (L.) Norlindh ssp. rotundata (DC.) Norlindh, is an invasive weed of coastal vegetation types in eastern Australia. It produces fleshy fruits, which are dispersed by birds and mammals. Compared with a range of vertebrate-dispersed fruits of native plant species that co-occur with naturalised C. monilifera, or occur elsewhere in south-eastern Australia, C. monilifera fruits and endocarps are intermediate in all dimensions and in the ratio of endocarp to pulp. C. monilifera fruits contain moderate quantities of sugars, but low quantities of protein and fat relative to many native fruits. Phenology, however, substantially distinguishes C. monilifera from co-occurring native plant species. C. monilifera produces fruits throughout the year, with the peak of production occurring in autumn to winter, a time when few native species in coastal vegetation produce fruits. Additionally, 9 of the 12 native species that do fruit, at least partly, over this period, differ substantially from C. monilifera in fruit morphology. C. monilifera, along with other invasive species, has substantially altered the temporal pattern of fruit availability in coastal vegetation. These fruiting characteristics have rendered C. monilifera fruits attractive to frugivores and have contributed to its successful spread.