BARKMAN, TODD J., JOEL R. MCNEAL, NELSON D. YOUNG, AND CLAUDE W. DEPAMPHILIS.* Department of Biology and Institute of Molecular Evolutionary Genetics, Penn State University, University Park, PA 16802 and Department of Biology, Trinity University, San Antonio, TX 78212. - Multiple origins of parasitism within angiosperms. Phylogenetic origins of parasitic angiosperm lineages have been difficult to study using DNA sequence data used previously because plastid genes and 18S rDNA may be lost or evolve at greatly accelerated rates making inferences uncertain. We present results of a large-scale sequencing study of conserved mitochondrial genes present in all plants regardless of their photosynthetic status. cox1 and atpA sequences were obtained from every order of angiosperm (recognized by APG, 1998), including every widely recognized hemi- and holoparasitic family. Phylogenetic analyses unambiguously place 12 major parasitic lineages within the context of angiosperm phylogeny. Origins of Balanophoraceae and Mitrastemonaceae are still uncertain and await further sampling. Several of the parasites appear to have arisen within lineages of plants they parasitize. This completely unexpected result suggests cases of adelophoparasitism or horizontal gene transfer from host to parasite.
BLARER, ALBERT*, DANIEL L. NICKRENT, HANS BÄNZIGER, PETER K. ENDRESS, AND YIN-LONG QIU. Institute of Systematic Botany, University of Zurich, Zollikerstr. 107, CH-8008 Zurich, Switzerland. - Phylogentic relationships among genera of the parasitic family Rafflesiaceae s.l. based on nuclear ITS and SSU rDNA, mitochondrial LSU and SSU rDNA, atp1, and matR sequences. We analyzed the sequences of nuclear ITS and SSU rDNA, and mitochondrial atp1, matR, and LSU and SSU rDNA (total length about 9000 bp) from 13 species and 9 genera of Rafflesiaceae s.lat. Separate and combined phylogenetic analyses of these six data sets gave consistent results. They identified four clades that were previously recognized as Rafflesiaceae s.s., Apodanthaceae, Cytinaceae, and Mitrastemonaceae. Furthermore, based on expanded unpublished analyses with other angiosperms, Mitrastemonaceae do not form a monophyletic group with the other Rafflesiaceae s.l. Bdallophytonforms a clade with Cytinus.
NOTE: The title of actual poster is: Phylogenetic relationship of Rafflesiales based on two nuclear and four mitochondrial genes. Additional analyses after the submission of this abstract have resulted in a monophyletic Rafflesiaceae s. lat., including Mitrastemonaceae. Click HERE to download a PDF file of this poster - BUT NOTE - the file is 1.8 MB in size, hence may take some time to download.
LI, JIANHUA1*, DAVID E. BOUFFORD2, AND MICHAEL J. DONOGHUE2. 1Arnold Arboretum of Harvard University, 125 Arborway, Jamaica Plain, MA 02130; 2Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA 02138. - Phylogenetics of Buckleya (Santalaceae) based on ITS sequences of nuclear ribosomal DNA. Buckleya Torr. (Santalaceae) is a hemi-parasitic shrubby genus with two species in China, on in Japan, and one in the sourheastern United States. Phylogenetic relationships among these species are controversial and have not been tested using molecular data. In this study we used sequences of the internal transcribed spacer region of nuclear ribosomal DNA to test previous phylogenetic hypotheses. Two sister species pairs are well supported: B. distichophylla plus B. graebneriana, and B. lanceolata plus B. henryi. Sequence differences and morphological characters support the recognition of B. lanceolata and B. henryi. Sequence divergence between B. distichophylla and B. graebneriana is twice as high as that between B. lanceolata and B. henryi. These results are most consistent with the treatment proposed by Carvell and Eshbaugh (1982). Biogeographically, one of the Chinese species (B. graebneriana) is most closely related to the eastern North American species (B. distichophylla), while the other Chinese spcies (B. henryi) is allied with the Japanese species (B. lanceolata). Maximum likelihood analyses do not reject clock-like evolution of nrDNA ITS spacers in Buckleya, and divergence times may date to the Late Miocene and Pliocene.
MCNEAL, JOEL R.* AND CLAUDE W. DEPAMPHILIS. Department of Biology and Institute of Molecular Evolutionary Genetics, Penn State University, University Park, PA 16802. - Origin and molecular systematics of the parasitic plant genus Cuscuta (dodder). The genus Cuscuta is composed of a large number of morphologically similar stem parasitic vines. They produce minute, scale-like leaves with flower structure that is often only discernable microscopically. The morphological reduction of Cuscuta has historically rendered them a taxonomically difficult group, although most authorities have agreed they are allied to Convolvulaceae (Morning Glories). Even molecular systematic approaches have proven confounding, as the chloroplast and nuclear genes most often used in broad phylogenies have been shown to evolve at accelerated rates in parasitic plants, sometimes leading to incorrect phylogenetic inferences. Mitochondrial gene and intron sequences have revealed a sister relationship of Cuscuta to members of Convolvulaceae rather than suggesting Cuscuta is nested within the family. A Nuclear ITS phylogeny provides insights into the relationships between the three traditionally recognized subgenera of Cuscuta along with a more detailed interspecific phylogeny. These relationships have a significant impact on the understanding of the evolution of parasitism and photosynthesis in Cuscuta.
NICKRENT, DANIEL L.1 AND VALERY MALECOT 2.* 1 Department of Plant Biology and Center for Systematic Biology, Southern Illinois University, Carbondale, IL 62901, USA, 2 Laboratoire de Paléobotanique, Université Pierre et Marie Curie, 12 rue Cuvier, 75005 Paris, France. - Phylogenetic relationships of Santalales based on nuclear small-subunit (18S) rDNA and plastid rbcL with special reference to Olacaceae.As currently classified, Santalales consists of 7 families of autotrophs, root- and aerial parasites. Within this order, Olacaceae present both non parasitic and root parasitic members and are thus key to understanding the origin of the parasitic habit. Sequences of nuclear ribosomal small subunit rDNA (18S) and chloroplast-encoded rbcL were used in a combined analysis to study phylogenetic relationships of the order. The present analysis include 51 genera of Santalales, 18 of which belong to Olacaceae (from a total of ca. 28 genera). As in previous analyses, Santalales are monophyletic with Opiliaceae, Loranthaceae and Viscaceae monophyletic and Santalaceae and Olacaceae paraphyletic. Sampling within Olacaceae is now sufficiently complete to comment about phylogenetic trends within the family. Although Schoepfia does not appear to be related to Olacaceae, its sister relationship with Misodendrum received 74% bootstrap support. Moreover, the clade between Schoepfia / Misodendrum and Loranthaceae had a 63% bootstrap value. The other members of Olacaceae are paraphyletic, and traditional classifications are only weakly supported. Tribe Couleae forms a well-supported clade (99% bootstrap). Most of section Anacolosoideae occurs in a clade (e.g. Strombosia, Strombosiopsis, Diogoa, Tetrastylidium and Scorodocarpus), except tribe Anacolosae (Anacolosa and Phanerodiscus in the present analysis). These latter two genera occur in a clade with Olax (Olaceae), Ongokea (Aptandrae) and Chaunochiton (Heisteriae). Malania, considered by European authors to belong to Olaceae, clearly belong to Ximeniae as suspected by its Chinese descriptors. Heisteria, the second member of tribe Heisteriae, does not cluster with Chaunochiton but occupies a more basal position in the family as does Erythropalum which has previously been classified in its own family (Erythropalaceae). Relationships within tribes of Olacaceae appear to be affected by choice of outgroup taxa. Several of these relationships are supported by morphological analysis, but further sampling of the family is needed, particularly for such unusual genera as Brachynema and Engomegoma.
To download a PDF version of this poster, click HERE.
RANDLE, CHRISTOPHER PATRICK. Department of Evolution, Ecology and Organismal Biology, Ohio State University, Columbus, OH 43202. - Biosystematics of Harveya Hook.(Orobanchaceae): preliminary studies. Harveya is a genus of root holoparasites in Orobanchaceae, distributed throughout southern Africa. Preliminary studies of herbarium material indicate that 19-25 species of Harveya inhabit South Africa, the center of diversity for this genus. Morphometric analysis of herbarium material was performed to establish species boundaries and morphological characters have been used to generate a preliminary phylogeny of this genus. Future work will involve inclusion of molecular data into phylogenetic analysis, a monograph based on natural groupings, and investigation of the evolution of photosynthetic loci in this holoparasite.
STEFANOVIC, SASA* AND RICHARD G. OLMSTEAD. Department of Botany, University of Washington, Box 355325, Seattle, WA 98195, USA. - Molecular systematics of Convolvulaceae inferred from cpDNA sequences. Convolvulaceae are a large family, comprising approximately 50-60 genera with some 1600-1700 species, the members of which present a rich diversity of morphological characteristics and ecological habitats. Previous efforts to systematize this diversity without a cladistic phylogenetic framework have disagreed on the circumscription of the family as well as tribal composition and relationship. In order to circumscribe the family and assess the relationships among its major lineages, a broad data set was constructed, containing representatives of all ten recognized tribes of Convolvulaceae plus representatives of putatively related families within Asteridae. This is done by using four chloroplast regions: rbcL, atpB, psbE-J operon, and trnL-trnF intron/spacer. The results indicate that Convolvulaceae are sister to Solanaceae, with 100% bootstrap support for each family and the clade comprising both families. Two of the three groups that have been proposed previously as segregate families, Cuscuta and Dichondreae, are nested within the Convolvulaceae in this analysis, and the third, Humbertia, is the sister to all other members of the family. The exact position of Cuscuta could not be ascertained, but some alternatives were rejected with confidence. The study identified several distinct monophyletic groups, some of which correspond to earlier ideas. Close relationships of tribes Hildebrandtieae with Cresseae and Ipomoeeae with Argyreieae (forming Echinoconieae) were confirmed. The polyphyly of Poraneae and Erycibeae is first reported in this study.
SENTERS1, ANNE E.*, DOUGLAS E. SOLTIS1, PAMELA S. SOLTIS1, MICHAEL ZANIS1, SANGTAE KIM2, JAMES D. THOMPSON1, AND ELIZABETH A. ZIMMER3. 1School of Biological Sciences, Washington State University, Pullman, WA 99164, 2Seoul National University, Seoul, Korea, 3Laboratory of Molecular Systematics, Smithsonian Institution, Washington D.C. 20560. - Phylogenetic relationships among eudicots based on a combined data set of four genes: rbcL, atpB, 18S rDNA, and 26S rDNA. Relationships among core eudicot clades (the asterid, rosid, Caryophyllales, Santalales, Berberidopsidales, and Myrothamnaceae/Gunneraceae clades) remain one of the last major questions of deep-level phylogeny in the angiosperms. To resolve these relationships, we assembled a large data set of entire 26S ribosomal DNA sequences for approximately 250 angiosperms. The 26S rDNA is just under 3.4 kb in length and consists of conserved core areas, as well as more rapidly evolving expansion segments. Because of is length and regions with different evolutionary rates, it appears to be highly useful for resolving relationships at this level. We constructed several different data sets and analyzed them using parsimony: 1) 26S rDNA sequences were added to the existing 567-taxon matrix (Soltis et al.), 2) a smaller data set was constructed for only those angiosperms for which all four genes were available. We also used a compartmentalization approach, reconstructing ancestral sequences for major clades. Our preliminary analyses provide additional support for the major core eudicot clades and the relationships of early-branching eudicots.
SMITH, R. ALAN*, DIANE M. FERGUSON, TODD J. BARKMAN, AND CLAUDE W. DEPAMPHILIS. Department of Biology, Vanderbilt University, Nashville, TN 37235 and Department of Biology and Institute of Molecular Evolutionary Genetics, Penn State University, University Park, PA 16802, and Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824. - Molecular phylogenetic evidence for the origin of Lennoaceae: A case of adelphoparasitism in the angiosperms? Lennoaceae are a small family of root parasites endemic to Mexico and the southwestern United States. These plants are non-photosynthetic and exhibit a reduction of morphological features which makes systematic placement difficult. Earlier studies of Lennoaceae based on floral and pollen morphology have suggested relationships with Boraginaceae, "Hydrophyllaceae," or Verbenaceae. Molecular evidence is presented from all three genomic compartments to test these hypotheses. The plastid gene rps2, the mitochondrial genes cox1 and atpA and the nuclear ITS region were sequenced and subjected to phylogenetic analysis. Preliminary results indicate that a monophyletic Lennoaceae is most closely related to Ehretioideae, a subfamily of Boraginaceae. This subfamily contains host plants of Lennoaceae, indicating a possible case of adelphoparasitism, the first such association suspected among the angiosperms. Further investigation should resolve this question and determine the closest extant relative of Lennoaceae among this group.
YOUNG, NELSON D.*, CAROLINE YOON, AND MITRA AZODI. Department of Biology, Trinity University, San Antonio, TX 78212. - Speciation by allopolyploidy in Castilleja: the case of C. dissitifora. Castilleja dissitiflora N. Holmgren is a montane species, endemic to central Nevada, and a tetraploid (2n=48). It is thought to be a genomic allopolyploid descendant of a cross or crosses between C. linariifolia Benth. (2n=24) and C. applegatei Fernald ssp. pinetorum (Fernald) Chuang & Heckard (2n=24). This hypothesized relationship is based on the fact thatC. dissitiflora is intermediate between the two putative parents in floral morphology and overall aspect. Although currently, C. dissitiflora is only sympatric with one putative parent, C. linariifolia, the other putative parent, C. applegatei ssp. pinetorum approaches it to within 200 km on the west and north of its range. It is commonly held that allopolyploids are most successful when the parents are not close relatives, for if they are, tetrasomic inheritance may generate unbalanced gametes. Although the two putative parents are both in subgenus Castilleja, C. linariiflora is is in section Castilleja, whereas C. applegatei is in section Viscidulae. The phylogenetic relationship among sections of Castilleja can reveal just how close or distant these two sections are. Sequences of the plastid trnK intron and nuclear ITS are used along with morphology and new chromosome counts to assess the validity of the hypothesized allopolyploidy. A skeletal phylogeny of the genus Castilleja is used to determine the degree of relationship between the sections with the two putative parent species. Castilleja is a member of the newly redefined Orobanchaceae.
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Last updated: 03-Oct-00 / dln