title: Evolution of woody life form on tropical mountains in the tribe Spermacoceae (Rubiaceae).
abstract: OBJECTIVE
  Spermacoceae are mainly an herbaceous group in the Rubiaceae. However, a few lineages are woody and are found in a diverse range of habitat types. Three of the largest woody lineages (Arcytophyllum,Hedyotis, andKadua) are characterized by their distribution in the moist tropical mountains and have disjunct distribution patterns with respect to their closest relatives. In this study, we explore the cases of derived woodiness in these three lineages and their diversification dynamics in the tropical mountains of Asia, the Pacific, and the Americas.
  
  
  METHODS
  By combining phylogenetic results with wood anatomical studies, we estimated timing of origin of the three woody groups, inferred their ancestral traits and ancestral distribution ranges, analyzed their associations with the tropical upland habitat, and elucidated their diversification across tropical mountains.
  
  
  RESULTS
  The three woody clades originated and diversified from herbaceous ancestors in close association with the tropical upland habitat during the Miocene. The ancestral range for Asian-PacificHedyotisis Africa/Madagascar and continental Asia for PacificKadua. The complex geological history of tropical Asia allowedHedyotisto diversify faster and create narrow endemics near oceans in the highlands of the Western Ghats in India, Sri Lanka, Southeast Asia including southeastern China, and New Guinea.
  
  
  CONCLUSIONS
  The three major woody clades in Spermacoceae have gained their woodiness independently from one another, subsequent to colonization by their ancestors from a different geographic environment. The evolution and diversification along the tropical mountain orogeny is strongly linked with the formation of woody habit and many narrow endemic species.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut 06269-3043 USA suman.neupane@uconn.edu.
authors.forename: Suman
authors.initials: S
authors.lastname: Neupane
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut 06269-3043 USA.
authors.forename: Paul O
authors.initials: PO
authors.lastname: Lewis
authors.affiliation: Botanic Garden Meise, Nieuwelaan 38, 1860 Meise, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Dessein
authors.affiliation: Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529-0266 USA.
authors.forename: Hunter
authors.initials: H
authors.lastname: Shanks
authors.affiliation: Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529-0266 USA.
authors.forename: Sushil
authors.initials: S
authors.lastname: Paudyal
authors.affiliation: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, NL-2300 RA Leiden, The Netherlands.
authors.forename: Frederic
authors.initials: F
authors.lastname: Lens
mesh_terms: D005075:Biological Evolution; D017753:Ecosystem; D010802:Phylogeny; D019666:Rubiaceae / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics*; D014934:Wood / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics
keywords: Rubiaceae; Spermacoceae; diversification; secondary woodiness; tropical mountains; wood anatomy