The role of sexual reproduction and water regime in shaping the distribution patterns of clonal emergent aquatic plants

Abstract

The reproductive characteristics of T. procerum in three lagoons in the Mediterranean south-east of South Australia were used to investigate the role of water regime in the often heterogeneous and patchy distribution of aquatic vegetation. A theoretical explanation for these patterns, based on sexual reproduction vis-a-vis seedling establishment, is proposed. Owing to the unpredictable nature of seed dispersal and the narrow range of suitable conditions for germination and establishment that result from fluctuating and variable water levels, establishment events are spatially and temporally dynamic. These features may be important for maintaining species distribution, species survival and habitat diversity. Population resilience through genetically heterogeneous stands is another outcome. The implications of sexual reproduction by clonal plants are discussed, as is the need to maintain the conditions that plants need to flower, germinate and become established. The unpredictable nature of establishment events makes them difficult to manage. Regulation and pondageldrainage may be having a profound effect on the survival of many aquatic plant species owing to their inability to regenerate under such conditions.