Effects of hydrology on recruitment of Pilularia minuta Durieu (Marsileaceae), an endangered plant of Mediterranean temporary pools

Hydrological requirements for germination and development of P. minuta were assessed through a 5-year field survey in Garâa Sejenane, Tunisia, and an experiment under controlled conditions. The spatial distribution of P. minuta was recorded in the field annually, while the experiment tested the effects of water levels and flooding dates on germination (the emergence of new individuals) and development. Water level was found to be the major factor affecting the germination and the development of P. minuta with flooding date as a secondary limiting factor. For germination to occur, the sediment must be completely waterlogged. Water depths of 5-10 cm are optimal for plant development. In addition, the plant needs a minimal flooding period of seven weeks to develop. Late-spring precipitation appears to be more critical than earlier rains.