Pollen Album of Rhizophora Members in Nigeria and Its Taxonomic Implications

Pollen samples of Rhizophora individuals in Nigeria Niger Delta were conducted to generate a pollen album. Samples were collected in permanent plots in Koko, Ogidigben (Delta State), Akakumama, Nembe (Bayelsa State), Olupiri-Epelema, Ugwede (Rivers State), Ikwe, Opolom (Akwa Ibom State), Adiabo Ukanabio and Esighi (Cross River State) between 2013 - 2016. A total of three hundred and sixty four (364) Rhizophora pollen samples were obtained from the sea water-land interfaces to 604 meters inland (maximum Rhizophora occurrence landward). The samples were prepared using standard Erdtmanian methods. The result showed the presence of five different shapes of tricolporate pollen. The exine sculptures were baculate, rugulate, striate and reticulate while the pollen shapes were either sub prolate, prolate or oblate. The polar shapes were circular in Operational Taxonomic Units (OTUs) 1 and 4, triangular in OTUs 2 and 3 and trilobate in OTU5. The grain arrangements for all five OTUs were monad. When this data was normalized and converted to numerical taxonomy using Euclidean distance, a loose relationship was observed between OTUs 1 and 2 suggesting distinct species.  Although, OTUs 3, 4 and 5 showed statistical difference (0.05 confidence limit) among themselves, analysis revealed no statistical difference to OTU 1 and 2, implying them as subtypes of either OTU.  The finding is in contrast to the widely held notion that only three putative Rhizophora species exist in Nigeria. Edaphic and genetic research of the two inferred species and three subtypes should be conducted.