Abstracts Dealing with Parasitic Angiosperms
Botany 2007
Chicago Hilton, Chicago USA, July 7-11, 2007

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Armstrong, Joseph E. [1], Borowicz, Victoria [2].
Ecology of a hemiparasite in a prairie community.
Hemiparasites interact with host plants on two trophic levels. While extracting water and nutrients from hosts they compete with them for these resources and for light. Based on observations of Pedicularis canadensis from two sites, we hypothesize that this hemiparasite is a strong parasite but a weak competitor, and so its impact on a community is context dependent: the hemiparasite exerts its effect through parasitism when competition for light is reduced. We predict that P. canadensis, a short perennial growing in a restored tallgrass prairie, will reduce productivity most under low nutrient conditions where vegetation is thin and light levels are consequently high, and least under high nutrient conditions where lush vegetation shades the hemiparasite and impedes photosynthesis and transpiration. To test this hypothesis we initiated a multi-year experiment in which 1 square meter quadrats were given one of eight treatments that were combinations of three factors: hemiparasite removal (or sham disturbance), mineral nutrient enhancement, or shade. The dry mass of hemiparasite, grasses, and forbs from the center of each plot was determined after one growing season. Nutrient enhancement nearly tripled grass biomass and doubled forb biomass on this poor-soil study site. Removal of the hemiparasite increased grass and forb biomass a little and this increase was most pronounced in unshaded plots where competition for light was low. Shade had minimal impact on host plants but decreased P. canadensis, especially in fertilized plots. We are encouraged by these early results, so the treatments will be continued.
1 - Illinois State University, Department of Biological Sciences, Campus Box 4120, Normal, Illinois, 61790-4120, USA
2 - Illinois State University, Department of Biological Sciences, Campus Box 4120, Normal, IL, 61790-4120, USA
Presentation Type: Oral Paper:Papers for Sections
Session: CP09
Location: Lake Ontario/Hilton
Date: Monday, July 9th, 2007
Time: 11:15 AM
Number: CP09005
Abstract ID:938

Tank, David C. [1], Olmstead, Richard [2].
Evolutionary history of perennial Castilleja (Castillejinae, Orobanchaceae): evidence from the nuclear gene waxy.
Perennial Castilleja are a morphologically and taxonomically complex group. This stems from complex morphological variation often attributed to the formation of polyploid complexes, where apparent hybrid swarms and morphological intergradation are common between some species. Molecular phylogenetic analysis of chloroplast and nuclear ribosomal DNA regions indicate that the perennial Castilleja clade (~160 spp.) is derived from a grade of annual Castillejinae taxa, including annual Castilleja species, Cordylanthus, Orthocarpus, and Triphysaria, suggesting that perenniality (restricted to Castilleja) evolved once from an annual ancestor. Significant shifts in diversification rate and short branch length estimates indicate that the perennial Castilleja clade has undergone a rapid and recent diversification. From the chloroplast and nuclear ribosomal DNA results, it was clear that more variable data would be needed to investigate the evolutionary history of species within the perennial Castilleja clade. Here we present phylogenetic analyses of the 3’ portion of the nuclear gene waxy, with an emphasis on the evolutionary history of the perennial Castilleja clade.  Evolutionary processes including lineage sorting and hybridization, in addition to implications for infrageneric classification of this taxonomically challenging group are discussed.
1 - Yale University, Peabody Museum of Natural History, Botany Division, P.O. Box 208118, New Haven, CT, 06520-8118, USA
2 - University of Washington, Department of Biology and Burke Museum, Box 355325, Seattle, WA, 98195, USA
Presentation Type: Oral Paper:Papers for Sections
Session: CP29
Location: Stevens 2/Hilton
Date: Tuesday, July 10th, 2007
Time: 11:15 AM
Number: CP29010
Abstract ID:1821

Morawetz, Jeffery J. [1], Randle, Christopher P. [2], Wolfe, Andrea D. [1].
Phylogeny and evolution of holoparasitism in the African clade of Orobanchaceae.
Parasitism in plants ranges from species that are still photosynthetic (hemiparasites), to those that have fully lost photosynthetic ability (holoparasites). Alectra is a primarily hemiparasitic genus that includes two holoparasitic species (A. alba; A. orobanchoides). Alectra alba is the least well known of these, occurring infrequently in forests in eastern-central Africa. Originally described as a species of Harveya, a primarily holoparasitic genus, this species was transferred to Alectra based on similarities in floral morphology (possessing the recurved style & stigma characteristic of Alectra). Vegetatively A. alba is quite distinct from other Alectra species in completely lacking pigmentation (the entire plant is white) and the scale-leaves typical of A. orobanchoides. Alectra alba is distinct from Harveya and other Alectra species in its host preference, growing on the roots of forest trees rather than parasitizing savanna grasses. Species of Harveya are generally thought to be holoparasites based on an achlorophyllous habit, with the exception of H. obtusifolia, which is by all appearances a hemiparasite, having chlorophyllous leaves that are not reduced to scales. This is the first phylogenetic analysis to include A. alba, and our combined three-gene dataset places it firmly within Harveya with high jackknife support. Further, the phylogenetic position of Harveya obtusifolia was examined.
1 - Ohio State University, Department of Evolution, Ecology and Organismal Biology, 300 Aronoff Laboratory, 318 W. 12th Ave., Columbus, Ohio, 43210-1293, USA
2 - Sam Houston State University, Department of Biological Sciences, 1900 Avenue I., Huntsville, TX, 77340
Presentation Type: Oral Paper:Papers for Sections
Session: CP29
Location: Stevens 2/Hilton
Date: Tuesday, July 10th, 2007
Time: 10:45 AM
Number: CP29008
Abstract ID:992

Morawetz, Jeffery J. [1], Wolfe, Andrea D. [1].
The evolution of rbcS in Orobanchaceae: a preliminary investigation.
The parasitic habit in plants ranges from species which are still photosynthetic, obtaining only mineral nutrients and water from their hosts (hemiparasites), to those which have fully lost photosynthetic ability, relying completely on their hosts for all nutrition (holoparasites). The evolution of holoparasitism places the genes involved in photosynthesis under relaxed functional constraint, allowing them to evolve rapidly. The Rubisco holoenzyme consists of eight small subunit (SSU) proteins, encoded by the nuclear gene family rbcS, and eight large subunit (LSU) proteins, encoded by the plastid gene rbcL. Formation of rbcL pseudogenes has occurred in some holoparasitic genera in Orobanchaceae, but several holoparasitic genera also retain an apparently functional copy of this gene. While the evolution of rbcL has been well studied in parasitic plants, no data exist on the evolution of rbcS. In those holoparasitic taxa with rbcL pseudogenes, rbcS may be free to evolve from functional constraints as well. Alternatively, the enzyme may be degrading independently within the chloroplast while the nuclear encoded SSU retains an intact open reading frame (ORF). In those holoparasites with intact rbcL ORFs, there may be compensatory changes in rbcS at sites of nonsynonymous substitution to preserve the tertiary structure of the Rubisco polypeptide to retain its functionality. We examined rbcS in 10 taxa spanning the range of nutritional dependencies within Orobanchaceae from non-parasites through holoparasites, including one member of Scrophulariaceae for comparison. rbcS appears to exist as three copies (800 bp, 650 bp, 250 bp) in many hemiparasitic taxa (including Sopubia and Cycnium), but as a single copy in the holoparasitic Hyobanche (1200 bp), Harveya (250 bp) and the hemiparasitic Buchnera (800 bp).
1 - Ohio State University, Department of Evolution, Ecology and Organismal Biology, 300 Aronoff Laboratory, 318 W. 12th Ave., Columbus, Ohio, 43210-1293, USA
Presentation Type: Oral Paper:Papers for Sections
Session: CP29
Location: Stevens 2/Hilton
Date: Tuesday, July 10th, 2007
Time: 11:00 AM
Number: CP29009
Abstract ID:1058

Tsai, Yi-Hsin Erica [1], Manos, Paul S. [1].
The hitchhiker’s guide to the forest: A parasitic plant’s account of the range expansion of its host.
Studies of population structure and range shifts of forest trees often have limited resolution due to lack of signal from slowly evolving DNA. In contrast, non-photosynthetic parasitic plants can offer a rich source of information because of their faster cpDNA mutation rates, faster generation times, and different life history characters. We use an obligate, host-specific, and highly selfing parasitic plant, Epifagus virginiana (beechdrop; Orobanchaceae), to trace the migration history and forest development of its host tree, Fagus grandifolia (American beech; Fagaceae). We present a range-wide, cpDNA based phylogeography of Epifagus and describe likely glacial refugia and post-glacial migration routes. These data are compared with the molecular phylogeography and paleo-pollen record of the host to elucidate the broader picture of beech forest development and post-glacial range expansion. We identify multiple glacial refugia for Epifagus, one or more giving rise to the diversity seen in the southern part of the range, and one located in the central Appalachians from which Epifagus migrated northward along the Appalachians then westward into the Midwest. These northern migration routes largely mimic changes in host density seen in the paleo-pollen record, but the Epifagus data provide additional, higher resolution information on how and when the beech climax community assembled. This study provides significant data on herbaceous plant migration that is currently missing and can answer broader questions about the cohesiveness of communities during migration and the development of post-glacial beech communities.
1 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
Presentation Type: Oral Paper:Papers for Topics
Session: CP33
Location: Lake Michigan/Hilton
Date: Tuesday, July 10th, 2007
Time: 3:00 PM
Number: CP33009
Abstract ID:1441


Davis, III, Charles C. [1], Latvis, Maribeth [2], Nickrent, Daniel L. [3], Wurdack, Kenneth J. [4], Baum, David J. [5].
Floral Gigantism in Rafflesiaceae.
Species of Rafflesiaceae possess the world's largest flowers (up to 1 meter in diameter), yet their precise evolutionary relationships have been elusive, hindering our understanding of the evolution of their extraordinary reproductive morphology. We present results of phylogenetic analyses of mitochondrial,nuclear, and plastid data showing that Rafflesiaceae are derived from within Euphorbiaceae, the spurge family. Most euphorbs produce minute flowers, suggesting that the enormous flowers of Rafflesiaceae evolved from ancestors with tiny flowers. Given the inferred phylogeny, we estimate that there was a circa 79-fold increase in flower diameter on the stem lineage of Rafflesiaceae, making this one of the more dramatic cases of size evolution reported for eukaryotes.
1 - Harvard University Herbaria, Organismic and Evolutionary Biology, 22 Divinity Avenue, Cambridge, MA, 02138, United States
2 - Harvard University Herbaria, Organismic and Evolutionary Biology, 22 Divinity Ave., Cambridge, MA, 02138, United States
3 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
4 - Smithsonian Institution, Department of Botany, NMNH mrc-166, Washington, D.C., 20013, United States
5 - University of Wisconsin, Department of Botany, 430 Lincoln Drive, Madison, WI, 53706, United States
Presentation Type: Oral Paper:Papers for Sections
Session: CP43
Location: Stevens 3/Hilton
Date: Wednesday, July 11th, 2007
Time: 10:45 AM
Number: CP43010
Abstract ID:2052

Cuscuta (Convolvulaceae)

Stefanovic, Sasa [1], Kuzmina, Maria [1], Costea, Mihai [2].
Phylogeny and biogeography of parasitic genus Cuscuta (dodders; Convolvulaceae).
Cuscuta, containing some 170-180 species, is nearly cosmopolitan in distribution and occurs in a wide range of habitats and hosts. Within this genus, three subgenera are traditionally recognized based primarily on the morphology of styles and stigmas. Previous molecular studies focused extensively on two of its largest subgenera, Grammica (~135 spp.) and Cuscuta (~30 spp.), and have delimited major groups within these taxa. However, because these studies were based on relatively fast evolving, non-coding DNA regions, the sequences were unalignable among different subgenera, thus preventing the phylogenetic comparison across the genus as a whole. In order to evaluate the current circumscription and assess the relationships among its major lineages, we conducted the first broad phylogenetic study on the entire genus Cuscuta using coding plastid and nuclear sequence data (rbcL and 26S rDNA) from a wide taxonomic sampling covering its morphological, physiological, and geographical diversity. The results indicate the presence of four well-supported clades. Two of them correspond entirely, or nearly so, to subgenera Monogyna and Grammica as traditionally defined. However, subgenus Cuscuta is found to be paraphyletic, with the South African members of this subgenus (from section Africanae) more closely related to subgenus Grammica. For a number of morphological characters, our phylogenetic results disagree with both their traditional taxonomic implications and directionality of scenarios of evolution as previously proposed. While several cases of long-distance dispersal are inferred, vicariance emerges as the most dominant biogeographical pattern for Cuscuta.
1 - University of Toronto at Mississauga, Biology, 3359 Mississauga Rd N, Mississauga, Ontario, L5L1C6, Canada
2 - Wilfrid Laurier University, Biology, 75 University Ave N, Waterloo, Ontario, N2L3C5, Canada
Presentation Type: Oral Paper:Papers for Sections
Session: CP05
Location: Lake Erie/Hilton
Date: Monday, July 9th, 2007
Time: 10:30 AM
Number: CP05009
Abstract ID:1131

Parasitic Plants, General

Lewis, Kristin [1], Sagi, Irit [2].
Plant-derived polyphenolics inhibit pectin methylesterase from parasitic plants.
Pectin methyl esterase (PME) is critical plant enzyme involved in cell changes associated with growth and cell elongation, and fruit ripening. It has also been implicated in the invasion of host tissue by parasitic plant haustoria, along with several other cell wall degrading enzymes. In fact, plants resistant to parasitism by other plant species have been shown to contain strong inhibitors of cell degrading enzymes such as PME in the surface of stem tissue. Residual PME activity is also responsible for degradation and “cloud loss” in processed fruit products such as juices. Pectin methyl esterase inhibitors have been identified previously from kiwi fruit and other naturally occurring sources, doubtless because of the importance of controlling PME activity in vivo. However, to our knowledge, the inhibitors identified to date are proteins. We have utilized a small organic molecule found in a common plant extract to strongly inhibit PME activity both in commercial extracts of the enzyme and in extractions of parasitic plants such as Cuscuta pentagona and Castilleja indivisa. We present the evidence for inhibition, data on inhibition levels and binding, and suggest potential uses for field control of parasitic plants in agricultural settings.
1 - Harvard University, Rowland Institute at Harvard, 100 Edwin H. Land Blvd., Cambridge, MA, 02142, USA
2 - Weizmann Institute of Science, Structural Biology, Rehovot, 76100, Israel
Presentation Type: Oral Paper:Papers for Sections
Session: CP60
Location: Williford C/Hilton
Date: Wednesday, July 11th, 2007
Time: 4:15 PM
Number: CP60004
Abstract ID:1447

NOTE: There are no parasitic liverworts.  The nutritional mode of Aneura is best described as mycoheterotrophic.
Wickett, Norman J. [1], Fan, Yu [2], Lewis, Paul O. [1], Goffinet, Bernard [1].
Plastid genome decay in parasitic plants: insight from the non-photosynthetic liverwort Aneura mirabilis.
The recently annotated, complete plastid genome sequence of the parasitic liverwort Aneura mirabilis revealed the complete functional loss of the chlororespiration (ndh) genes, pseudogenes for major subunits of photosystem I, photosystem II, and the cytochrome b6f complex, and an inversion of psbE and petL. The designation of pseudogenes was made using genomic comparisons with the phylogenetically distant liverwort Marchantia polymorpha. In order to correlate functional gene losses with the evolution of a heterotrophic life history, we sampled several populations of A. mirabilis and its photosynthetic sister groups and sequenced plastid regions homologous with the losses detected in the plastid genome sequence. A functional gene loss or the psbE-petL inversion was never detected in a photosynthetic liverwort. All the gene losses and the psbE-petL inversion were detected in every population of the non-photosynthetic liverwort sampled. The rates of synonymous and non-synonymous substitutions were estimated for eight pseudogenes and six genes to detect whether they are evolving under relaxed purifying selection. Here we present evidence that A. mirabilis has recently acquired an obligately heterotrophic life history, and that large deletions and structural rearrangements may play an important role in the functional reduction of the plastid genome, rather than a relaxation of a synonymous substitution bias, early in the shift to parasitism.
1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
2 - University of Connecitcut, Ecology and Evolutionary Biology, 75 N. Eagleville Rd., Storrs, CT, 06268, United States
Presentation Type: Oral Paper:Papers for Sections
Session: CP14
Location: Lake Huron/Hilton
Date: Monday, July 9th, 2007
Time: 5:00 PM
Number: CP14016
Abstract ID:2033

SIUC / College of Science / Parasitic Plant Connection
URL: http://www.parasiticplants.siu.edu/meetings/Bot2007ParAbstracts.html
Last updated: 06-Aug-08 / dln