Taxonomy and biogeography of Sundaland Gardenia (Rubiaceae) / Low Yee Wen

Low , Yee Wen (2010) Taxonomy and biogeography of Sundaland Gardenia (Rubiaceae) / Low Yee Wen. Masters thesis, University of Malaya.

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Abstract

In Southeast Asia, the genus Gardenia J.Ellis (Rubiaccae) is poorly understood and documented due to a lack of country revisions, contentious species delimitations and accumulation of poorly identified material in herbaria. This study reviewed the taxonomic history and position of the genus, and revised the taxonomy of Sundaland species (including those of Sumatra. the Malay Peninsula, Java_ Borneo, Palawan and adjacent islands). It includes a survey and cladistic study of morphological characteristics, and phylogenetic ana lyses using two chloroplast regions (atpB-rbcL and trnT-F) and the nuclear ITS region of representative species from Sundaland and adjoining regions. Twelve species are native to Sundaland and another two from mainland Asia and Wallacea commonly cultivated. Important generic characters include a woody shrub to tree habit with the growth architectural models of Leeuwen berg and Scarrone; resinous buds; tubular stipules; so litary terminal nowers; and pollen in tetracls. Calyx characters were the most use ful for species di stinction. Comparative morphological studies allowed two very closely related species, G. e/ata and G. tubijera, to be distinguished; G. tubi}era var. subcarinuta to be raised to species rank; and G. c/o/ichantha to be subsumed under the synonymy of G. griffithii. Several new species (G. beamanii Y. W.Low and G. chanii Y. W.Low) and varieties (G . . rnbcarinata var. sumatrcnia Y. W.Low and G. el at a var. kinaba/ue11sis ined.) were diagnosed. An identification key to Sundaland taxa, species descriptions, notes and identification lists are provided. The genealogies produced showed that Sundaland lineages were largely distinct from mainland Asian ones, probably renecting the biogeographic distinction of these regions. Limited introgression of the mainland lineage including G. jasminoides into the lineage with G. chanii was detected. There was evidence for reticulate evolution among Sundaland lineages indicated by discordant genealogies of chloroplast and nuclear regions. lntrogression of the widespread Sundaland species G. elata into a lineage with Lhe more locally restricted G. Beamanii (Borneo) was probably enabled by increased chances of contact during Pleistocene sealevel rn inima, when lowland forest area was contiguous between present-day Peninsular Malaysia and Borneo. Local variation in genetic characteristics implies that current for rest fragmentation in Sundaland could dimini sh the species va riab ility of G. elata. A complex of rarer species mostly occurring in pockets in peat swamps (G. chanii, G. griflthii, G. pteroca/yx, G. tubifera) and adjacent kerangas fo rests (G. cosllllata) would also be threatened by habitat disturbance and transformation.

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