Syzygium Gaertn. is the largest genus in the Myrtaceae family and is infamous in the tropics for its seeming lack of nonvariable characters for delimitation and its long-standing confusion with the large genus Eugenia L. which has resulted in a huge number of synonyms. Regional treatments of the African-Indian Ocean region (continental Africa, Madagascar and the Comoros Islands and the Mascarenes and the Seychelles), in which 66 species have so far been recognised, is presented here. This includes four new combinations, three new names and six species new to science (Syzygium comorensis Byng, Syzygium humbertii Byng, Syzygium labatii Byng, Syzygium mortonianum Byng, Syzygium pyneei Byng, Florens & Baider, and Syzygium rakotonasoloanum Byng). Detailed descriptions, species keys, habitat notes, conservation status, distribution maps, specimens examined, and illustrations and photos are given. Continental Africa harbours the largest number of species (21), followed by Madagascar (19), Mauritius (16), La Réunion (4), Comoros Islands (3), and the Seychelles (1). Phylogenetic relationships of the genus in the African-Indian Ocean region were reconstructed using nuclear (ITS and ETS) and plastid (matk, ndhF and rpl16) sequence data. African-Indian Ocean species form a monophyletic group within the species rich subg. Syzygium and can be broadly divided into four geographical groups. Particular focus was aimed at the Syzygium guineense (Willd.) DC complex, where along with sequence data, phenetic analysis of 25 characters from 134 herbarium specimens of the S. guineense complex were analysed. Molecular data suggests that the complex is polyphyletic and several subspecies should be elevated to specific rank but phenetic data shows that morphologically they are difficult to separate without provenance information. Increased sampling of the genus seems to increase resolution of the group and this is illustrated by the near complete sampling of the Mascarene clade. This fully resolved Mascarene clade is divided into two broad groups with morphological characters shaped by their ecological habitats and potential pollinators.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:629403 |
| Date | January 2014 |
| Creators | Byng, James W. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=215097 |
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