Low genetic diversity and high genetic differentiation among severely fragmented populations of the critically endangered tree Talbotiella gentii (Fabaceae)

The genetic diversity among 17 populations (including 10 newly discovered) of Talbotiella gentii (Fabaceae, Caesalpinioideae), a rare tree species endemic to Ghana, was assessed using random amplified polymorphic DNA (RAPD). A total of 80 polymorphic bands were generated from eight primers and analysed by cluster and correspondence analysis. This showed a clear distinction between populations, with two major groups associated with geographical origin. AMOVA analysis showed that 94.05% of the genetic variation was partitioned among populations, while only 5.95% was found within populations suggesting little gene flow between populations. Possible reasons for the high population genetic differentiation and the low levels of genetic variation within populations are inbreeding and genetic drift. Of a total of 26 known populations, 14 are now extinct, five during the course of this study. Action to prevent complete extinction of the species is therefore urgent.