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Title: Phylogenetics and characterisation of Lamiaceae tribe Ocimeae, subtribe Ociminae
Author: Althobaiti, Ashwaq T.
ISNI:       0000 0004 8508 2403
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2019
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Phylogenetic analyses of the subtribe Ociminae (Lamiaceae) based on four plastid DNA regions (trnL–trnF intergenic spacer, trnH-psbA intergenic spacer, matK and rps16 intron) and two nuclear DNA regions (ITS and ETS) are presented. Bayesian inference was utilized for the reconstruction of phylogenies and for the assessment of statistical support for clades. The phylogeny was used for the investigation of the clade in terms of the distribution of morphology and geography. The subtribe Ociminae is monophyletic and can be simply diagnosed by morphological synapomorphies and is of African origin. The results clarify the relationships among Orthosiphon and its related genera Fuerstia and Hoslundia. Orthosiphon is monophyletic with exclusion Or. fruticosus, and it is a sister to Fuerstia and Hoslundia. Because Fuerstia and Hoslundia formed a monophyletic group with high morphological similarity between them, these genera will be merged under the earliest name Hoslundia. Ocimum is monophyletic with the inclusion of subgenus Nautochilus. Ocimum subgenus Nautochilus is a sister to the rest of Ocimum (subgenus Ocimum and subgenus Gymnocimum). Surprisingly, Orthosiphon fruticosus is a member of subgenus Nautochilus and highly supported, therefore, nomenclatural changes are required if the groups are to remain monophyletic. Analysis displayed strong congruence between the combinable component consensus trees and the traditional classification for most of genera and the results supported by morphological and geographic distribution. However, more taxon sampling to cover some regions of geography missed in this study is required. Moreover, the efficiency of ITS, matK, trnH-psbA and in combination for species identification of Orthosiphon was assessed. For DNA barcode analysis, the determination of intraspecific and interspecific divergence, assessment of barcoding gap, reconstruction of phylogenetic trees and evaluation of barcode regions for species identification (based on best match and best close match) were carried out. The results revealed that ITS is a significant barcode region for identifying Orthosiphon species as a single marker and, for the combination, ITS+matK+trnH-psbA.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral