Western North American Naturalist Volume 68 Number 2 Article 4 6-10-2008 Hybridization between a rare and introduced Oenothera along the north Pacific Coast Matthew L. Carlson University of Alaska, Anchorage Robert J. Meinke Oregon State University, Corvallis Follow this and additional works at: https://scholarsarchive.byu.edu/wnan Recommended Citation Carlson, Matthew L. and Meinke, Robert J. (2008) "Hybridization between a rare and introduced Oenothera along the north Pacific Coast," Western North American Naturalist: Vol. 68 : No. 2 , Article 4. Available at: https://scholarsarchive.byu.edu/wnan/vol68/iss2/4 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Western North American Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Western North American Naturalist 68(2), © 2008, pp. 161–172 HYBRIDIZATION BETWEEN A RARE AND INTRODUCED OENOTHERA ALONG THE NORTH PACIFIC COAST Matthew L. Carlson1 and Robert J. Meinke2 ABSTRACT.—Interspecific hybridization has increasingly become regarded as a serious threat to the genetic integrity and persistence of rare plants. Oenothera glazioviana (Onagraceae) is a horticultural species that has escaped cultivation and now threatens the narrow Pacific coastal endemic O. wolfii with hybridization. Reports of morphologically intermediate and ecologically aggressive forms prompted this investigation into the extent of hybridization over the range of O. wolfii. In particular, this study identifies populations of pure and hybrid origins. We used multivariate methods to characterize the morphological variation of Oregon and northern California coastal Oenothera populations. Putatively pure O. wolfii and O. glazioviana individuals do not overlap in many floral characteristics. We found morphologies ranging between the 2 species in northern California populations, however, supporting the inference of hybridization. Remote O. wolfii populations in Oregon were smaller in almost all characters, and discriminant analysis was able to distinguish the rare species from both hybrids and O. glazioviana. However, 5 of 10 O. wolfii populations overlapped significantly with hybrid populations for individual traits and composite morphology, and trait values outside the range of O. wolfii were discovered in 2 populations previously considered to be pure. We also discuss the morphological evidence in light of these species’ chromosomal complexes and environmental factors. Key words: hybridization, introgression, Oenothera, conservation, rare plants, permanent translocation heterozygotes, morphometric analysis. Understanding the processes and potential of native species (Ellstrand 1992, Albert et al. impacts of hybridization becomes more impor- 1997, Wolf et al. 2001) and affect local environ- tant as related allopatric species are brought mental and genetic adaptation, especially in into contact by anthropogenic dispersal with narrowly distributed species of unique habitats. increasing frequency (Ellstrand and Elam Along the southern Oregon and northern 1993, Albert et al. 1997, Abbott and Lowe 2004, California Pacific Coast, an escaped introduced Prentis et al. 2007). Many cases of hybridization ornamental, Oenothera glazioviana Micheli. ex between native and introduced or between Mart., is apparently hybridizing with the rare, rare and common plants have been reported native species, O. wolfii [Munz] Raven, W. (Rogers et al. 1982, Brochmann 1984, Freas Dietr. & Stubbe. While O. wolfii is threatened and Murphy 1988, McGranahan et al. 1988, by habitat loss and alteration due to coastal Liston et al. 1990, Reiseberg 1991, Stace 1991, development, roadside maintenance activities, Ellstrand 1992, Levin et al. 1996, Rhymer and and recreation activities (Skinner and Pavlik Simberloff 1996, Daehler and Strong 1997, 1994), the most serious threat is hybridization Imper 1997, Vilà et al. 2000, Gisler 2003, Malik with O. glazioviana (Dietrich et al. 1997, Gisler et al. 2006), some with dramatic effects on the and Meinke 1997, Imper 1997). success of the introduced species (Thompson The habitats of these 2 species are gener- 1991, cf. Prentis et al. 2007). Often hybridiza- ally dissimilar. Oenothera glazioviana occurs tion results in more aggressive and successful in weed-lots, garden disposal sites, and occa- genotypes (Heiser 1965, Thompson 1991, Ell- sionally along roadsides, while O. wolfii prefers strand and Schierenbeck 2000, Whitney et al. natural coastal bluffs and upper beaches. In 2006), and models indicate that hybridization northern California, however, considerable de - can dramatically hasten extinction of native velopment up to the beach strand has brought species (Wolf et al. 2001, and see Prentis et al. garden-grown O. glazioviana in contact with 2007). The addition of new genes via hybrid - O. wolfii. Although hybrids appear to have ization can also threaten the genetic integrity greater ecological amplitude than either parent, 1Alaska Natural Heritage Program, Environment and Natural Resources Institute, University of Alaska–Anchorage, 707 A Street, Anchorage, AK 99503. E-mail: [email protected] 2Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331-2902. 161 162 WESTERN NORTH AMERICAN NATURALIST [Volume 68 they nevertheless tend to occupy more dis - Oenothera glazioviana is a very large-flow- turbed areas, such as imported substrates along ered biennial, often growing over 150 cm in roadsides (Dietrich et al. 1997, Imper 1997). height. Normally restricted to gardens, it occa- The hybrids are fertile (Carlson and Wierck sionally establishes outside developed areas. unpublished data) and capable of very rapid Flowers are ≥6.0 cm in diameter, deep yel- expansion. Hybrids appear to be expanding low-colored petals overlap broadly, and the rapidly along a coastal highway corridor be - stigma is strongly exerted. This species origi- tween Eureka, California, and Oregon, in most nated in Europe by hybridization be tween cases adjacent to current or historic pure O. cultivated or naturalized North American wolfii populations. At 1 site the population species (Cleland 1972, Raven et al. 1979, Wag- size of hybrids jumped from 100 to 7000 in 2 ner 1993). The pistillate parent is suggested to years (Imper 1997). The northernmost popula- be O. biennis or O. grandiflora and the stami- tions of O. wolfii are relatively remote and buf - nant parent is likely O. elata (O. hookeri), a fered by natural habitats; these populations are species cultivated in European gardens for thought to be free from the immediate threat many years (Raven et al. 1979). The stabilized of hybridization, but O. glazioviana has been hybrid was traded as an ornamental by the observed in anthropogenic habitats on the 1860s and appears to have been transported central Oregon coast, completely overlapping around the world quickly, as its species descrip - the rare species’ range. tion was published in 1882 from Brazilian type The objective of this study was to charac- specimens (Raven et al. 1979). terize the morphological variation of individu- Both species are permanent translocation als and populations relative to putatively pure heterozygotes (Dietrich et al. 1997), a cytolog- O. wolfii and thus estimate the extent of the ical condition that influences patterns of fertil- hybridization in O. wolfii. Specifically, we asked ity and morphological variation (Holsinger and if the morphological variation in coastal Oen - Ellstrand 1984). This system is characterized othera plants is consistent with widespread by extreme genetic linkage. In O. wolfii all 14 hybridization and introgression (i.e., a high chromosomes form a single ring in meiosis, frequency of individuals that are variable and and a ring of 12 and a bivalent occur in O. intermediate between parental species). Addi- glazioviana (Cleland 1972, Dietrich et al. 1997). tionally, using a morphological analysis, we Oenothera wolfii has an AA genomic and a asked which populations appear to have hybrid, plastome I constitution (Wasmund and Stubbe introgressed, or a mixture of individuals from 1986, Dietrich et al. 1997). Both A complexes the parental species. It is hoped that these produce nearly identical phenotypes. Oenothera methods will be combined with molecular glazioviana has an AB genomic and plastome analysis and that the results will aid conserva- III constitution (Stubbe 1964) and is the only tion and recovery efforts in maintaining O. outcrossing permanent translocation heterozy- wolfii populations and limiting negative impacts gote in the Onagraceae (Raven 1979). For a of the invasive O. glazioviana. more complete discussion of permanent trans - location heterozygosity, see Cleland (1972), METHODS Holsinger and Ellstrand (1984), Chiu and Sears (1993), and Deitrich et al. (1997). Study Species Because genetic recombination is stifled, Oenothera wolfii is a showy biennial to populations of permanent translocation het- short-lived perennial, forming large popula- erozygotes are highly uniform genetically and tions in modestly disturbed upper beach sites; have been considered microspecies, resulting however, populations are few and isolated. The in considerable taxonomic confusion (see Diet- species ranges from 50 to 200 cm tall. Flowers rich et al. 1997). Theoretically there is little are generally less than 4.0 cm in diameter