Diversity and fine-scale spatial genetic structure of Cyperus papyrus populations in Lake Naivasha (Kenya) using microsatellite markers

摘要

Papyrus in tropical swamps regenerate vegetatively and through seeds. The study investigated clonal diversity of Cyperus papyrus bordering Lake Naivasha (Kenya). Three regions within the lake were investigated aiming to detect fine-scaled structure in a lakeward transect, including two sites subject to recent dynamic changes, namely a seedling zone and a harvested zone. Using microsatellites, out of 279 ramets, 271 were genets, with most allelic variation observed at individual level but little at site or region level, resulting in very high gene flow levels. At lake level a PCoA grouped lakeward samples distinctly from the landward sites. Somewhat higher inbreeding levels were observed in landward zones but only the harvested site had all loci significantly deviating from the equilibrium implicating the impact of a 6-monthly harvesting regime. A1,500 m lakeward transect revealed a spatial genetic structure at short distance whereas a very small isolation-by-distance supported a continuous distribution model. The seedling zone contained the highest allelic diversity and individual seedlings were assigned to the nearest shoreline transect, suggesting localized seed rains. Highly diverse C. papyrus swamps of Lake Naivasha are hypothesized to originate mainly from seedling recruitment at short distances, such mature stands can maintain high clonal diversity.