Molecular Systematics and DNA Barcoding of African Sapindaceae
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Date
2011-10
Authors
Adeyemi, Temitope
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Abstract
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.
Description
Keywords
Sapindaceae, Conservation, Plant Systematics, Phylogenetics