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https://hdl.handle.net/2142/72548
Description
Title
Systematics of Malesian Acalypha (Euphorbiaceae)
Author(s)
Sagun, Vernie G.
Issue Date
2008
Doctoral Committee Chair(s)
Levin, Geoffrey A.,
Department of Study
Plant Biology
Discipline
Plant Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Biology, Botany
Paleontology
Abstract
A comprehensive survey of the pollen morphology and ultrastructure of Acalypha, molecular phylogenetic analyses, and a systematic revision of Malesian Acalypha was undertaken. Using light microscopy, scanning and transmission electron microscopy, the palynological study shows that Acalypha pollen is generally small and brevicolporate. Acalypha pollen exhibits significant variation in size, aperture number, aperture distribution and exine ornamentation, contradicting earlier reports that Acalypha pollen is homogeneous. Though the pollen morphology generally is inconsistent with a phylogeny based on a preliminary analysis of combined ITS and ndhF sequence data, some characters show trends that are consistent with the basal position of subgenera Linostachys and Androcephala. Pollen characters also provide support for several small clades found in the molecular phylogeny. However, pollen morphology is not consistent with relationships among the Malesian Acalypha species.
The molecular phylogenetic analyses using the nuclear gene ITS and chloroplast genes ndhF and trnL-F confirm that Acalypha is monophyletic, as is subgenus Acalypha. The basal groups in the genus and its closest outgroup, Mareya, consist of African species, suggesting an African origin of the genus followed by dispersal to the Americas and Asia, including Malesia. The Malesian species do not form a monophyletic group although the molecular data strongly support two small clades within the region. Each of these clades is morphologically homogeneous. The classification system of Pax and Hoffmann appears to be unsatisfactory and incongruent with the phylogenetic analyses.
In the systematic revision of Malesian Acalypha, 28 species are recognized. Acalypha paniculata is the sole member of subgenus Linostachys in Malesia and the rest of the species belong to subgenus Acalypha. Three previously synonymized species and three previously classified as infraspecific taxa are now considered to be distinct species, and four species names are newly reduced to synonymy. This revision will be incorporated in the systematic treatment of the Euphorbiaceae in Flora Malesiana, a long-term international project coordinated in Universiteit Leiden in the Netherlands, and will also contribute to regional floras of the Malesian region, including the Flora of Peninsular Malaysia and the Tree Flora of Sabah and Sarawak.
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