Systematics/Phytogeography / Taxonomie/ Section
Randle, Christopher P. , Williams, Justin , Lee, Stephen M. , Zychowski, Gregory V. , Reid, Ryan L. .
Host preference in leafy mistletoe, Phoradendron serotinum (Santalaceae).
Phoradendron serotinum is a hemiparasite that infects woody plants of Mexico and the United States. It has been the subject of taxonomic controversy, having been variously divided into additional species and subspecies. In the most recent and comprehensive treatment of the genus, variation in diagnostic characters among four subspecies is continuous, making host preference useful in distinguishing them. Seed germination appears to be mediated by the drying of the viscous layer that surrounds the seed and adheres it to the branch. Germination success appears to be independent of the physical structure of its substrate. On the other hand, haustorial disk formation, a preliminary sign of infective capability, is limited by the particular substrate provided by the host species. In previous studies of populations of P. serotinum subsp. tomentosum from central Texas, offspring of plants grown on one host species were poorly suited to infect a different host species. In east Texas, three of the subspecies overlap morphologically and geographically, making subspecific identification difficult. Although many other oak species and other deciduous dicotyledonous trees occur naturally in the area, infection on trees other than Quercus nigra is uncommon. In assessing host preference, it is important to document not only the local abundance of host species that are parasitized, but also the abundance of species that do not serve as hosts. In a pilot study conducted during the winter of 2007, all trees on the campus of Sam Houston State University were visited, identified, and surveyed for mistletoe infection, to test the following hypotheses: 1) Parasites exhibit preference for certain host species, 2) Parasites are unable to grow on some potential host species. Differences in host preference across the range of P. serotinum were also explored.
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1 - Sam Houston State University, Department of Biological Sciences, 1900 Avenue I, Huntsville, TX, 77340, USA
2 - Baylor University, Department of Environmental Studies, Waco, TX, 76798-7266, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Room 6/Woodward
Date: Tuesday, July 29th, 2008
Time: 11:45 AM