@ARTICLE{TreeBASE2Ref21611, author = {Livia Wanntorp and Melanie Grudinski and Paul I. Forster and Alexandra N. Muellner-Riehl and Guido Grimm}, title = {Wax plants (Hoya, Apocynaceae) evolution: Epiphytism drives successful radiation.}, year = {2014}, keywords = {Epiphytism, Hoya, Indo-Australian Archipelago (IAA), Indo-Burma region, intrageneric relationships, intergeneric relationships, monsoon, nuclear spacers, plastid spacers, phylogenetic incongruence.}, doi = {10.12705/631.3}, url = {http://}, pmid = {}, journal = {Taxon}, volume = {63}, number = {1}, pages = {89--102}, abstract = {Hoya is a species-rich, mostly epiphytic genus within tribe Marsdenieae (Apocynaceae) and occurs in tropical and subtropical forests of the Indomalayan and Australasian realms, including the Indo-Australian Archipelago (IAA). Earlier studies have found some phylogenetic structure within the genus but also incongruences between nuclear and plastid DNA markers. Here we show how the use of a necessary large taxon sampling in combination with genetic incongruence can influence even more negatively the reconstruction of phylogenetic inference. These problems can be overcome by the exclusion of rogue taxa from the data set and the subsequent analysis of general molecular differentiation patterns. Evolution and diversification of Hoya in the tropical forests of the IAA region are presented and possible ecological and morphological parameters forming the base of biogeographic patterns are proposed. Results Despite marked incongruence, the analysis of four gene regions shows that most species of Hoya group in six major lineages (Clade I?VI) with conspicuous geographic distribution. The earliest diverging epiphytic lineages are restricted to subtropical continental Asia (Clade I) or tropical to subtropical Australasia (Clade IV), whereas their non-epiphytic relatives are limited to the tropical Indomalayan (Clade II/III) and Australasian (Clade II) parts of the IAA. Clade V (tropical Indomalaya and Australasia) and Clade VI, with outposts in the Himalayas, Japan, and throughout Australasia, represent the second phase of diversification within Hoya. The remaining species show either strongly conflicting signal indicative of lineage crossing or are phylogenetically ambiguous with sequences that are intermediate or ancestral to sequences characteristic of the major clades, in particular, Clade V and VI. Conclusions Hoya is suggested to have a tropical to subtropical Indo-Burma/Himalayan origin, coinciding with the onset of the monsoon climate during the Himalayan uplift. The subsequent dispersal of Hoya into the many subareas of the IAA region and eventually Australia and the Southwest Pacific, and its successful and explosive radiation there, are linked to its epiphytic life style, a trait that is today rarely found among angiosperms. } }

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