Cyperus papyrus in Lake Victoria: Genetic Information, Utilisation and Resource Sustainability

Many wetlands in the Lake Victoria basin are dominated by Cyperus papyrus, which are very productive and, therefore, have an important role both ecologically and socially. The increasing harvesting pressure of papyrus threatens its future. Thus, a conservation approach was employed to determine the intensity of the pressure and threat to the papyrus diversity at clonal level. Eight microsatellite loci were used for analysing the clonal diversity and genetic diversity of Cyperus papyrus in 6 swamps of Mwanza bay (Tanzania) and 5 swamps of Nyanza bay (Kenya). From 304 individuals, we observed a total of 49 alleles in Mwanza bay and 44 alleles in Nyanza bay, a high clonal diversity (R = 0.64 to 1 Mwanza bay and R=0.70 to 1 in Nyanza bay), and a high genetic diversity (HE) with an average of 0.558 and 0.493 for Mwanza and Nyanza bay, respectively. The analysis of molecular variance showed that most of the allelic variances were within individuals. This resulted in a moderate differentiation (FST, 0.126 and Nm, 1.7) from all studied population in Lake Victoria. Gene flow was high between populations within each bay of the Lake (Nm > 4). The observed disturbance in the swamps showed no effects on any of the papyrus diversity variables. The clonal diversity (R) was even higher in the disturbed swamps than in pristine ones, with values ranging from 0.78 to 1 for disturbed, and 0.64 to 1 for pristine swamps. This explains that, although it is a clonal plant, papyrus maintains sexual reproduction and successful seed dispersal, making them resilient to even strong environmental and anthropogenic disturbance.