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Variations in species richness among biological groups has often been considered an important macroevolutionary problem. Recently the explanations for these differences have been sought using new, more efficient methodologies and phylogenetic analyses. Variation in clade diversification rates (speciation minus extinction rate) could explain disparity in clade size. Therefore, identifying correlations between traits and this variation is necessary to hypothesise potential drivers of speciation responsible for affecting clade species richness. In this work, these problems have been investigated using Myrtaceae as a case study, with particularly attention focused on the BKMMST clade sensu Biffin et af. (2010). The clade contains two large genera (>500 species; sensu Frodin, 2004) mostly fleshy fruited (Eugenia and Syzygium), whilst the other genera in the clade are relatively species poor and predominantly dry fruited. It has been suggested that fleshy fruits could be the key innovation responsible for the hyper diversification of these large BKMMST genera but the hypothesis was never tested. In this study, an improved molecular dataset of Myrtcaeae was used to investigate macroevolutionary questions at a high taxonomical level. Previously unsampled new taxa were sequenced for a total of 143 taxa and four gene regions, the nuclear ITS and plastid matK, ndhF and rpL16 regions. The results confirmed the existence ofthe BKMMST clade and improved resolution and support among the BKMMST tribes. However, in the hypothesised phylogenetic tree, many of the deep nodes still remain poorly supported. A temporal approach was applied to understand the evolutionary patterns, and for the first time, a diversification rate shift was placed within the BKMMST clade, confirming the presence of fast radiation event associated with the clade. In, addition, a selection of abiotic (biogeography patterns) and biotic traits (flower colour, fruit type and habitat) were tested in order to explain the origin of the shift identified and/or the origin of the larger clades within the BKMMST.

Taxonomic revision and phylogeny study of Tristaniopsis Brongn. & Gris (Myrtaceae) of Borneo is presented. Based on the current circumscription, by examining specimens in major herbaria and in the field, 22 species are recognised in Borneo, including 11 new to science. Identification key to species was produced, and followed with individual species taxonomic treatments. Morphological descriptions and distribution maps, plus notes on habitat and etymology, together with a list of specimens examined, are presented for each species. Taxonomic and nomenclatural problem were also reviewed, species level problems were resolved, resulting in clearly defined species. Based on the specimens examined its clearly shown that more exploration should be undertaken to collect from the vast area of Kalimantan, especially the kerangas forest which is rich in endemic species in the other parts of Borneo. For field identification a field key to species was prepared, which supported with a set of pictorial plates showing the major morphological characters for each species (22 plates) were presented using photos taken in this study. Each plate is followed with a legend to explain all the characters shown in the plates. To avoid confusion with the nearest species, diagnostic characters were presented to distinguish them. In addition to this, a vernacular name is proposed for each species to avoid confusion since, previously, some vernacular names were used for more than one species or a general name, such as pelawan-pelawan or selunsur, was used for all Tristaniopsis species. Molecular studies using ITS (Internal Transcribe Spacer) nuclear ribosomal DNA, plus 2 plastid regions (rbcL and matK) chloroplast DNA were done. All three regions and the combinations have produced low resolution especially within the Bornean sub-clade in tree topologies which were produced using three methods Neighbor-Joining (NJ), Maximum Parsimony (MP) and Maximum Likelihood (ML). Although there was often low resolution, the data clearly resolved Tristaniopsis according to the two geographic regions, Borneo, and non-Borneo (New Caledonia and Australia), these two sub-clade received >90% support in NJ, MP and ML analyses. Only the ITS nuclear DNA clearly supported Tristaniopsis as a monophyletic genus. There was very poor correspondence of morphological characters with the topology of the plastid and ITS phylogeny. Sample of T. whiteana from Sentosa Island, Singapore, was placed separated from T. whiteana of Borneo, though morphologically there are good species, this shows that there are variation of sequences between-region. This suggests that a broader sequencing project is needed, which require greater sampling of Tristaniopsis from its distribution range, which can be expanded to sequence taxa from the neighboring countries, Papua New Guinea, Indonesia (include Sulawesi) and the Philippines in the east, and Peninsular Malaysia, Sumatra, Thailand, and Myanmar in the west, to assess patterns of distribution and to hypothesize dispersal routes. Base on the result, Tristaniopsis may have originated from New Caledonia and Australia, with subsequent dispersal into the Malesian region up to Thailand and Tenasserim in Burma the northernmost extent of the distribution range.