Landscape Genetics and Ecological Niche Modeling of Afzelia quanzensis (Pod Mahogany)

The Forest refuge hypothesis seem to explain the distribution of African tropical plants. A review of 16 studies established that refugial plant populations are located in putative Pleistocene refugia in tropical Africa, unlike in tropical South America. During cold and dry spells of the Pleistocene, tropical African plants were repeatedly restricted into refugia, from where they expanded during warm and mesic conditions. Maxent modeling of the current distribution of Afzelia quanzensis show occurrence in eastern and southern African countries, such as Kenya, Tanzania, Mozambique, Zimbabwe, Zambia, Malawi, and Angola. Forecasting the distribution to 2050 and 2070 showed a range increase. Climate change may not negatively impact the distribution of A. quanzensis. Illumina shotgun sequencing was used to develop microsatellite loci in A. quanzensis. After screening 70 potential loci, 39 consistently amplified. Twelve loci were polymorphic, and eight successfully cross-amplified in a congeneric species, A. africana. Sequencing produced an enormous number of potential loci, and dinucleotide repeats were most polymorphic. Ten of the 12 polymorphic loci were used to investigate genetic impact of the Kalahari-Zimbabwe axis, a mountain range that separates low altitude plant populations in Zimbabwe. A total of 192 samples were genotyped, 135 in the north and 57 in the south of the Kalahari-Zimbabwe axis. Genetic diversity was relatively low across the samples (observed heterozygosity = 0.466, expected heterozygosity = 0.452, number of alleles = 4.367, allelic richness = 2.917, effective number of alleles = 2.208, and private allelic richness = 0.197). Two gene pools were detected, one made up predominantly of southern individuals, and the other of northern individuals. A genetic barrier was detected that coincided with the Kalahari-Zimbabwe axis. There was limited gene flow between northern and southern individuals. Germplasms for conservation or preservation should be collected from both northern and southern populations in order to capture the entire extant genetic diversity of the species. Illegal logging should be discouraged to avoid the continued decline of genetic diversity.