Monitoring Hydrilla Using Two RAPD Procedures and the Nonindigenous Aquatic Species Database
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J. Aquat. Plant Manage. 38: 33-40 Monitoring Hydrilla Using Two RAPD Procedures and the Nonindigenous Aquatic Species Database PAUL T. MADEIRA,1 COLETTE C. JACONO,2 AND THAI K. VAN1 ABSTRACT South-east Asia north through China and into Siberia and west to Pakistan. It has a disjointed range in Africa and Hydrilla (Hydrilla verticillata (L.f.) Royle), an invasive northern Europe (Cook and Lüönd 1982, Pieterse 1981). aquatic weed, continues to spread to new regions in the Unit- Since its introduction hydrilla has spread aggressively through- ed States. Two biotypes, one a female dioecious and the oth- out the United States. A dioecious female biotype, first iden- er monoecious have been identified. Management of the tified in 1959 (Blackburn et al. 1969) was reported to have spread of hydrilla requires understanding the mechanisms of been introduced from Sri Lanka to Florida in the early 1950s introduction and transport, an ability to map and make avail- by a tropical fish and plant dealer (Schmitz et al. 1990). The able information on distribution, and tools to distinguish the current range of this plant is throughout the south with sepa- known U.S. biotypes as well as potential new introductions. rate distributions in California (Yeo and McHenry 1977, Yeo Review of the literature and discussions with aquatic scien- et al. 1984). A second introduction was reported in 1976 from tists and resource managers point to the aquarium and water Delaware and from the Potomac river around 1980 (Haller garden plant trades as the primary past mechanism for the 1982, Steward et al. 1984). This second biotype is monoecious regional dispersal of hydrilla while local dispersal is primarily and has spread across the central Atlantic states (Kay 1992, carried out by other mechanisms such as boat traffic, inten- Langeland 1996). It is seemingly more adapted to areas with tional introductions, and waterfowl. The Nonindigenous short growing seasons (Van 1989) and is capable of producing Aquatic Species (NAS) database is presented as a tool for as- viable seed (Langeland and Smith 1984, Conant et al. 1984). sembling, geo-referencing, and making available informa- As hydrilla and other nonindigenous aquatic species tion on the distribution of hydrilla. A map of the current spread, the need for resource management tools to track in- range of dioecious and monoecious hydrilla by drainage is festations increases. Aquatic plant monitoring programs, the presented. Four hydrilla samples, taken from three discrete, most extensive and up to date sources for spatial data on non- non-contiguous regions (Pennsylvania, Connecticut, and indigenous plants, are not equally available nationwide. After Washington State) were examined using two RAPD assays. polling natural resource agencies from all 50 states, Bartodz- The first, generated using primer Operon G17, and capable iej and Ludlow (1997) reported that only seven states con- of distinguishing the dioecious and monoecious U.S. bio- duct full scale aquatic plant monitoring programs. Twenty types, indicated all four samples were of the monoecious bio- states have partial programs, that is, they are limited in the type. Results of the second assay using the Stoffel fragment number of waters, plant species, or years surveyed. Twenty and 5 primers, produced 111 markers, indicated that these three states are without programs. Other sources for occur- samples do not represent new foreign introductions. The dif- rence information on nonindigenous plants may be obscure ferences in the monoecious and dioecious growth habits and and are widely dispersed (Jacono and Boydstun 1998). This management are discussed. study demonstrates the use of the Nonindigenous Aquatic Key words: Randomly amplified polymorphic DNA, Hydrilla Species (NAS) Database for cataloging and presenting spatial verticillata, monoecious, dioecious, spread, dispersal. relationships from the available occurrence data on hydrilla. The two hydrilla biotypes may occur simultaneously in the INTRODUCTION same water body or within the same region. Ryan et al. (1995) first reported the occurrence of the dioecious biotype Hydrilla (Hydrilla verticillata (L.f.) Royle) is an invasive in a lake with an existing monoecious population. In the ab- aquatic weed whose range in the Old World is vast. It extends sence of flowering, the two biotypes can sometimes be distin- from New Zealand and Australia through many of the South- guished by their growth habit. The dioecious biotype initially west Pacific Islands, the Philippines, Taiwan, and Japan (Cook grows vertically producing a dense surface mat while the mo- and Lüönd 1982, Pieterse 1981). In Asia it extends from noecious initially spreads horizontally along the sediment with less vertical elongation (Van 1989). Nevertheless, hydril- la’s growth habit displays a great deal of environmental plas- 1U S. Department of Agriculture, Agricultural Research Service, Invasive ticity. To distinguish the biotypes accurately Ryan and Plant Research Lab, 3205 College Avenue, Fort Lauderdale, FL 33314. Received Holmberg (1994) and Ryan et al. (1995) used the molecular for publication March 2, 1999 and in revised form September 21, 2000. assay known as random amplified polymorphic DNA (RAPD). 2U.S. Department of the Interior, U.S. Geological Survey, 7920 NW 71st Street, Gainesville, FL 32653. They displayed a single polymorphic marker, generated J. Aquat. Plant Manage. 38: 2000. 33 using primer Operon G17, hereafter referred to as the “G17 some necrosis, and with a heavy epiphytic crust (Aufwuchs) of fingerprinting reaction”, which is present in the dioecious algae and bacteria. Those from Mason Island arrived in biotype but absent in the monoecious. healthy condition. To serve as controls, dioecious hydrilla While the use of a single diagnostic molecular marker pro- from Florida and California and monoecious hydrilla from vides a useful tool for distinguishing between the two U.S. North Carolina and Delaware were selected from the USDA biotypes, it cannot eliminate the possibility of a third, sepa- collection along with “nearest (foreign) neighbor” plants rate introduction. To answer questions of genetic similarity from Bangalore, India and Seoul, Korea. “Nearest neighbor” one must increase the number of markers. Madeira et al. plants were selected because they were the most similar ge- (1997) used a RAPD procedure to examine the phenetic re- netically to the biotypes presently found in the U.S. accord- lationships among 44 accessions of hydrilla from various re- ing to the RAPD analysis of Madeira et al. (1997). While the gions of the world, generating 85 polymorphic markers for Bangalore plant served as an outlier to (clustered immediate- the analysis. Dioecious samples from Florida, Texas, and Cal- ly outside of) the U.S. dioecious accessions, the Seoul plant ifornia clustered closely before joining a cluster from the In- integrated into (clustered with) the U.S. monoecious sam- dian subcontinent. Eight monoecious samples from North ples. Therefore a sample from Rawa Pening, Indonesia, one Carolina, Maryland, Virginia and Delaware clustered togeth- of the closest related accessions to the U.S. monoecious sam- er along with an accession from Seoul, Korea. These data re- ples in the previous study (aside from Seoul) was included as inforced the widely held impression that there have been two an outlier. Apical stem fragments from each collection were foreign introductions. However, when domestic introduc- thoroughly rinsed in a jet of deionized water to remove as tions appear in regions widely separated geographically from much epiphytic material as possible, then blotted dry. Next, the nearest infestation, it seems relevant to re-investigate approximately 50 mg total wet weight of leaves was placed in- whether they represent foreign introductions or further dis- to a 1.5 ml microcentrifuge tube and stored in an ultracold persion by one of the two existing biotypes. freezer (-80C) until removed for DNA extraction. The second goal of this paper, therefore, is to demonstrate DNA extraction, RAPD Amplifications and Gel Electrophoresis. the utility of molecular techniques in answering questions of Total DNA was extracted using the CTAB method of Doyle biotype or origin using several geographically isolated sam- and Doyle (1990) as “micro” modified by Van and Madeira ples. The G17 fingerprinting reaction used to distinguish (1998). The DNA solution was quantified using fluorometry U.S. biotypes is repeated and followed by a more detailed ex- and stored at 4 C. Two different RAPD reactions were used. amination using the Madeira et al. (1997) multi-primer phe- The first is the G17 fingerprinting reaction used by Ryan et netic analysis to determine whether samples might represent al. (1995) to distinguish the U.S. monoecious and dioecious new foreign introductions. Three infestations (four samples), biotypes with the dNTP modification noted by Les et al. characterized by geographical separation from established (1997). The second, multiprimer reaction used AmpliTaq distributions, were selected for examination. DNA Polymerase, Stoffel fragment (Perkin Elmer3), the same five primers (Operon Technologies: A4, A6, B20, G11, G14), MATERIALS AND METHODS and the reaction conditions used by Madeira et al. (1997) to analyze a world-wide collection of hydrilla. This reaction was Plant material. The first sample, collected in 1996 by the used for the phenetic analysis. Amplifications were replicat- 58’48”N, senior author from the Schuylkill River (39° ed at least three times. Amplification products were electro- 75 11’52”W) was, at the time this study began, both the first ° phoresed on 2% agarose (Sigma) gels, visualized by report of hydrilla in Pennsylvania, and the northernmost ethidium bromide staining, and photographed using a FO- continuation of the existing range of the monoecious biotype TO/Analyst Minivisionary System (Fotodyne, Inc.). known for the central Atlantic states. The second sample was Phenetic Analysis. Loci were scored for the presence (1) or provided by Kathy Hamel (Washington State Department of absence (0) of bands and characterized by the primer used Ecology) and Ernie Marquez (Resource Management) from followed by the size in base pairs.