Flowering, fruiting, germination and seed dispersal of the newly emerging weed Solanum mauritianum Scop. (Solanaceae) in the wet tropics of north Queensland
S.K. FlorentineA,B, M. CraigA and M.E. WestbrookeB
A School for Field Studies, Centre for Rainforest Studies, Yungaburra, Queensland 4872, Australia.
B School of Science and Engineering, University of Ballarat, PO Box 663, Victoria 3350, Australia.
Summary
Solanum mauritianum (wild tobacco) has recently become a weed of major concern in some agricultural production areas, and tropical rainforest restoration sites, of the Atherton Tablelands, north Queensland. Until recently, little was known about the ecology of this species. A study was conducted to examine: (i) the flowering, fruiting pattern, (ii) seed germination pattern, (iii) density of soil stored seed bank, and (iv) potential avian seed dispersers of S. mauritianum. Flowering and fruiting patterns were studied on randomly selected plants within the study site over a period of 35 days. A germination study was performed on green (unripe) and yellow (ripe) fruits with seeds from green fruits germinating faster than seeds collected from yellow fruits. The density of germinable seeds in the soil seed bank was determined from 94 samples collected beneath the canopy of 24 randomly selected S. mauritianum plants. Of seedlings that germinated, 73% were S. mauritianum and seedling density of S. mauritianum averaged 16 000 seedlings per hectare.
To determine the role of birds in the dispersal of S. mauritianum seeds, observations were made of all birds visiting eleven fruit-bearing plants. To examine the bird's excrement, birds were captured in mist-nets, their excrement collected and any seeds present identified. A total of 340 seeds from 15 plant species were obtained. Four tropical rainforest birds (Australian king parrots (Alisterus scapularis), brown cuckoo doves (Macropygia amboinensis), spotted catbirds (Ailuroedus melanotis) and silvereyes (Zosterops lateralis)) consumed seeds of S. mauritianum and were potential seed dispersers.
Results suggest that S. mauritianum possessed ideal weed traits such as copious seed production, and high seedling recruitment from soil stored seed. Its use in rainforest restoration plantings should be discouraged as it may aid the spread of the species on the Atherton Tablelands.
Key words: avifauna, seed germination, Solanum mauritianum, soil seed bank, weed.
Plant Protection Quarterly (2003) 18 (3) 116-120.