title: What does it take to resolve relationships and to identify species with molecular markers? An example from the epiphytic Rhipsalideae (Cactaceae).
abstract: OBJECTIVE
  The Cactaceae are a major New World plant family and popular in horticulture. Still, taxonomic units and species limits have been difficult to define, and molecular phylogenetic studies so far have yielded largely unresolved trees, so relationships within Cactaceae remain insufficiently understood. This study focuses on the predominantly epiphytic tribe Rhipsalideae and evaluates the utility of a spectrum of plastid genomic regions. •
  
  
  METHODS
  We present a phylogenetic study including 52 of the 53 Rhipsalideae species and all the infraspecific taxa. Seven regions (trnK intron, matK, rbcL, rps3-rpl16, rpl16 intron, psbA-trnH, trnQ-rps16), ca. 5600 nucleotides (nt) were sequenced per sample. The regions used were evaluated for their phylogenetic performance and performance in DNA-based species recognition based on operational taxonomic units (OTUs) defined beforehand. •
  
  
  RESULTS
  The Rhipsalideae are monophyletic and contain five clades that correspond to the genera Rhipsalis, Lepismium, Schlumbergera, Hatiora, and Rhipsalidopsis. The species-level tree was well resolved and supported; the rpl16 and trnK introns yielded the best phylogenetic signal. Although the psbA-trnH and trnQ-rps16 spacers were the most successful individual regions for OTU identification, their success rate did not significantly exceed 70%. The highest OTU identification rate of 97% was found using the combination of psbA-trnH, rps3-rpl16, trnK intron, and trnQ-rps16 as a minimum possible marker length (ca. 1660 nt). •
  
  
  CONCLUSIONS
  The phylogenetic performance of a marker is not determined by the level of sequence variability, and species discrimination power does not necessarily correlate with phylogenetic utility.
authors: Nees-Institut für Biodiversität der Pflanzen, Universität Bonn, Germany. n.korotkova@uni-bonn.de
authors: Nadja
authors: N
authors: Korotkova
authors: Thomas
authors: T
authors: Borsch
authors: Dietmar
authors: D
authors: Quandt
authors: Nigel P
authors: NP
authors: Taylor
authors: Kai F
authors: KF
authors: Müller
authors: Wilhelm
authors: W
authors: Barthlott
mesh_terms: D029421:Cactaceae / Q000235:genetics*; D017931:DNA Primers; D018744:DNA, Plant / Q000235:genetics; D017343:Genes, Plant; D005819:Genetic Markers
chemical_list: D017931:DNA Primers; D018744:DNA, Plant; D005819:Genetic Markers