THE ROLE OF SEXUAL REPRODUCTION AND WATER REGIME IN SHAPING THE DISTRIBUTION PATTERNS OF CLONAL EMERGENT AQUATIC PLANTS

The reproductive characteristics of T. procerum in three lagoons in th e Mediterranean south-east of South Australia were used to investigate the role of water regime in the often heterogeneous and patchy distri bution of aquatic vegetation. A theoretical explanation for these patt erns, based on sexual reproduction vis-a-vis seedling establishment, i s proposed. Owing to the unpredictable nature of seed dispersal and th e narrow range of suitable conditions for germination and establishmen t that result from fluctuating and variable water levels, establishmen t events are spatially and temporally dynamic. These features may be i mportant for maintaining species distribution, species survival and ha bitat diversity. Population resilience through genetically heterogeneo us stands is another outcome. The implications of sexual reproduction by clonal plants are discussed, as is the need to maintain the conditi ons that plants need to flower, germinate and become established. The unpredictable nature of establishment events makes them difficult to m anage. Regulation and pondage/drainage may be having a profound effect on the survival of many aquatic plant species owing to their inabilit y to regenerate under such conditions.