Introduction
The prawns of the genus Macrobrachium comprises about 243 species globally and plays important ecological roles as well as human food source. However, there is little information known about the phylogenetic relationships of the Kenyan/East African and other global congener species for better understanding of its evolutionary relationships, palaegeographic and diversification patterns among this group of species as well as sustainable aquaculture fisheries.
Methods: A multi-locus gene approach was used to reconstruct the phylogeny of Macrobrachium species to its congener species in the Neo- and Palaeotropics based on a concatenated data set of Cytochrome Oxidase 1 (COI), 16S rRNA, Histone 3 and 18S rRNA genes. All the laboratory molecular work was carried out at Johann Wolfgang Goethe University Frankfurt/main, Germany between year 2015-2018 and all sequences reposited in gene bank.
Results: Four species of Macrobrachium were confirmed to occur in Kenya namely, Macrobrachium rude, M. dolichodactylus, M. equidens and M. lepidactylus. The phylogenetic tree results also confirmed the genus Macrobrachium as monophyletic although the Kenyan/East African Macrobrachium species were not monophyletic and formed three distinct monophyletic clades that clustered well with the Indian, East and South East Asian sister species indicating their close genetic similarity. This suggest allopatric speciation after larval drift of Macrobrachium in the Indian Ocean occasioned by favorable surface ocean currents that provided ecological connectivity although it is a rare event in geological time scales. However, M. lepidactylus appeared in an isolated position on the phylogenetic tree and clustered with sister species from Africa only, suggesting endemicity to the African continent.
Conclusion: The results of this study support the evolution of species with abbreviated larval development (hololimnetic) occurring multiple times being non- monophyletic and occurred in different lineages suggesting multiple origins. In summary, this study has generated new information regarding evolutionary history of Kenyan/African Macrobrachium species for informed conservation and management measures and sustainable aquaculture.
Key words: Macrobrachium, phylogeny, monophyly, larval drift, allopatric speciation