Clonal Structure of Two Wild Lotus (Nelumbo nucifera Gaertn.) Populations Inferred from Amplified Fragment Length Polymorphism Fingerprints

The lotus Nelumbo nucifera often forms dense populations at the margins of lakes and ponds. Many aquatic plant species such as N. nucifera are characterized by the ability to reproduce both sexually and asexually, which can affect the genetic diversity of populations growing in different types of environments. We compared the clonal diversities of two natural lotus populations in Japan. Diversity was quantified by DNA fingerprinting of amplified fragment length polymorphisms (AFLPs) in leaves sampled across each population. The DNA fingerprints revealed different amounts of diversity in each population. In 162 samples from Lake Kasumigaura, where lotus has grown continuously for many years, 35 AFLP patterns were detected. One particular clone was distributed widely, suggesting that growth of seed-derived plants was inhibited because of the superior competitive ability of rhizomes, resulting in low genetic diversity within the population. In 214 samples from Uchi-numa Pond in Miyagi Prefecture, where the lotus population was totally destroyed by heavy rains in 1998 and is now recovering, 213 different AFLP profiles were detected. The spatial distance between samples from Uchi-numa Pond was correlated with the genetic distance. These results suggest that, in lotus, sexual reproduction is favored when rapidly varying water level damages the population, because small seedlings are better able to survive in a low-density population. In contrast, vegetative reproduction is favored when environmental conditions are stable.