title: Molecular phylogeny of Larrea and its allies (Zygophyllaceae): reticulate evolution and the probable time of creosote bush arrival to North America.
abstract: Nucleotide sequences of Rubisco Large Subunit (rbcL) and the internal transcribed spacers (ITS) of nrDNA were obtained for the five species of Larrea and one species each of Bulnesia (ITS only) and Plectrocarpa (rbcL only). Parsimony analyses were conducted, including sequences from seven genera of Zygophyllaceae reported by other authors-Kallstroemia, Zygophyllum, Augea, Fagonia, Pintoa, Guaiacum, and Porlieria. The main conclusions of the present study are (1) the Argentine endemic Plectrocarpa tetracantha belongs to the subfamily Larreoideae (New World Clade); (2) all three phylogenies obtained from rbcL, ITS, and combined data sets show a close relationship between the tetraploid L. cuneifolia (sect. Bifolium) and the diploid multifoliolate pair L. nitida-L. ameghinoi (sect. Larrea), which could result from a possible intersectional hybrid origin of the tetraploid; (3) L. divaricata (sect. Bifolium) and L. tridentata (sect. Bifolium) form a highly supported monophyletic group, which agrees with previous cytogenetic and molecular evidence; and (4) the rate of nucleotide substitution of rbcL was estimated based on geological and fossil records. Under the molecular clock hypothesis, nucleotide sequence divergence between L. divaricata and L. tridentata suggests a Late Neogene (8.4 to 4.2 mybp) time of arrival of the diploid ancestors of L. tridentata to North American deserts.
authors.affiliation: Departamento de Cs. Biológicas, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina.
authors.forename: V V
authors.initials: VV
authors.lastname: Lia
authors.forename: V A
authors.initials: VA
authors.lastname: Confalonieri
authors.forename: C I
authors.initials: CI
authors.lastname: Comas
authors.forename: J H
authors.initials: JH
authors.lastname: Hunziker
mesh_terms: D002467:Cell Nucleus / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D005843:Geography; D008969:Molecular Sequence Data; D009154:Mutation; D009656:North America; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D010944:Plants / Q000145:classification / Q000235:genetics*; D012273:Ribulose-Bisphosphate Carboxylase; D017422:Sequence Analysis, DNA; D013997:Time Factors
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant; D021903:DNA, Ribosomal Spacer; D010940:Plant Proteins; C101625:RbcL protein, plastid; D012273:Ribulose-Bisphosphate Carboxylase