Molecular Phylogenetics and Biogeography of the Caribbean-Centered <Emphasis Type="Italic">Croton</Emphasis> Subgenus <Emphasis Type="Italic">Moacroton</Emphasis> (Euphorbiaceae s.s.) |
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Authors: | Benjamin W van Ee Paul E Berry Ricarda Riina Jorge E Gutiérrez Amaro |
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Institution: | (1) Department of Botany, University of Wisconsin-Madison, 430 Lincoln Dr., Madison, WI 53706, USA;(2) Department of Ecology and Evolutionary Biology, University of Michigan Herbarium, 3600 Varsity Drive, Ann Arbor, MI 48108, USA;(3) Jardín Botánico Nacional, Carretera del Rocío, Km 32, CP. 19230, Calabazar, Boyeros, Havana, Cuba;(4) Present address: Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, USA |
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Abstract: | Initial molecular phylogenetic studies established the monophylly of the large genus Croton (Euphorbiaceae s.s.) and suggested that the group originated in the New World. A denser and more targeted sampling of Croton species points to a South American origin for the genus. The nuclear and chloroplast genomes indicate a different rooting
for the phylogeny of Croton. Although we favor the rooting indicated by the chloroplast data our conclusions are also consistent with the topology inferred
from the nuclear data. The satellite genera Cubacroton and Moacroton are embedded within Croton. These two genera are synonimized into Croton and a new subgenus, Croton subgenus Moacroton, is circumscribed to include them and their allied Croton species. Croton subgenus Moacroton is morphologically characterized by a primarily lepidote indumentum, bifid or simple styles, and pistillate flowers with
sepals that are connate at the base. This newly circumscribed subgenus is found from North America to South America, and in
contrast to the majority of Croton species most of its members are found in mesic habitats. The group is most diverse in the greater Caribbean basin. A molecular
clock was calibrated to the phylogeny using the available Euphorbiaceae fossils. The timing and pattern of diversification
of Croton is consistent with both the GAARlandia and Laurasian migration hypotheses. A single species, Croton poecilanthus from Puerto Rico, is placed incongruently by its nuclear and chloroplast genomes. The possibility of this species being of
hybrid origin is discussed.
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Keywords: | Caribbean biogeography Croton Euphorbiaceae GAARlandia Moacroton Molecular phylogenetics |
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