Molecular Systematics and DNA Barcoding of African Sapindaceae
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Sapindaceae Jussieu is a family of flowering plants in the order Sapindales. They exist as trees and shrubs, and tendril-bearing vines with about 140-150 genera and 1400-2000 species worldwide. Sapindaceae is economically, medicinally and aesthetically useful. The aims of this research are to carry out systematic study on African Sapindaceae and generate DNA barcodes for each species with a view to sharing the DNA barcode sequence in a public database. The taxonomy of the family was re-examined using both classical and modern approaches; essentially, the phylogeny of the family was expounded. The methodology employed included: herbaria studies, morphological and anatomical characterization, species distribution modelling and molecular studies. These revealed that in Africa, the family is represented by twenty eight (28) genera and a hundred and six (106) species. They are geographically distributed in the temperate and tropical regions of the world and their distribution is mostly affected by the minimum temperature of the coldest month (35.4%) and least affected by minimum temperature of driest quarter (0.2%). In the family, exo morphological features recorded were compound leaves (paripinnate, imparipinnate or trifoliate); flowers are in spirits, fruits occur as berry, drupe or capsule and contain seed with white or orange aril. Taxonomically useful endo-characteristics were rectangular, polygonal and irregular cell shapes, smooth, curved and undulate anticlinal wall patterns, amphistomata distinguished Dodonaea viscosa and Sapindus saponaria from other species in the family. Generally, two stomatal types were recorded and these were anomocytic and paracytic. Trichome types found in the family included acicular, filiform, uniseriate, glandular and stellate types and they proved useful in taxa delimitation. Epicuticular wax is granular in all taxa especially on the adaxial surface. For molecular studies, silica gel dried specimens’ yielded good quality DNA unlike the old dried herbarium leaf samples. Two hundred and four (204) DNA sequences and sixty-nine (69) DNA barcodes were generated. Barcode data which was hinged on matK and rbcL sequence data have been in the Barcode of Life database (BOLD) website for public use. The phylogenetic analyses revealed that Sapindaceae is monophyletic but paraphyly and polyphyly were shown at subfamilial and tribal levels. The recent suggestion on the taxonomic position of Xanthoceras sorbifolia, Aceraceae and Hippocastanaceae as belonging in the family is corroborated. The family can therefore be classified and supported as follows: Sapindoideae (100% bp), Dodonaeoideae (57% bp), Hippocastanoideae (including Aceraceae) (66% bp) and the monotypic Xanthoceroideae (< 50% bp) comprising Xanthoceras is sister to the family. Furthermore, based on only molecular data, Sapindaceae can be subdivided into subfamily Sapindoideae with twelve tribes and subfamily Dodonaeoideae with three tribes.
Sapindaceae, Conservation, Plant Systematics, Phylogenetics