Genetic structure of Hydrilla verticillata L.f. Royle in eastern China and the Republic of Korea: Implications for surveys of biological control agents for the invasive monoecious biotype

Extensive interlineage hybridization in the predominantly clonal Hydrilla verticillata

“…Monoecious plants were discovered in Delaware in 1976 and spread subsequently to every state from North Carolina to Maine (Les et al, 1997;Madeira et al, 2000), as well as to California, Georgia, Indiana, Washington, and Wisconsin (Keller, 2007;Jacono et al, 2019b). Although both U.S. biotypes for the most part are triploid (Harlan et al, 1984;Langeland, 1989;Les et al, 1997), other genetic, morphological, and physiological differences have been documented between monoecious and dioecious plants, including distinct plastid sequences (Madeira et al, 2004(Madeira et al, , 2007Williams et al, 2018), microsatellite signatures (Williams et al, 2018), vegetative morphologies (Ryan et al, 1995), isozyme profiles (Verkleij and Pieterse, 1991;Nakamura et al, 1998), and tuber production patterns (Scannell and Webb, 1976;Steward and Van, 1987;Sutton et al, 1992;Nakamura and Kadono, 1993).…”

“…Intraspecific hybridization could be possible among hydrilla lineages that are genetically distinct, with some plastid clades having diverged ~6.71 mya (Zhu et al, 2015). Besides being genetically distinct, many plastid lineages are relatively isolated across the wide geographic range of the genus, allowing them to evolve independently (Stebbins, 1950;Cook and Lüönd, 1982;Williams et al, 2018). Hybridization, whether interspecific between nonindigenous and native species or intraspecific between individuals from different donor ranges, may produce novel genotypes that enhance adaptation to new environments (Ellstrand and Schierenbeck, 2000;Moody and Les, 2002;Bossdorf et al, 2005), and this possibility becomes a serious consideration in the context of invasive hydrilla populations.…”

“…Biological control of invasive species depends on accurately identifying taxa in order to search for taxon-specific control agents in the native range of the invader (Balciunas et al, 2004;Williams et al, 2018). Indeed, knowing the genetic background and makeup of invasive species can be critical for developing effective chemical and biological treatments (Solarz and Newman, 2001;Parks et al, 2016;Williams et al, 2018), for avoiding impacts to native species (Moody et…”

“…Each invasive species may require a specific management approach, because the treatment for one species may not be effective against other species, or even variants of the same species (Moody et al, 2008). Certain treatment options, including biocontrol and herbicides, may have variable efficacy depending on the genotype of the target species (Michel et al, 2004;Williams et al, 2018). Moreover, land managers often find themselves in an arms race to maintain effective treatment options for species that respond by evolving resistance to control methods (Müller-Schärer et al, 2004).…”

Suitability of introduced Nymphoides spp. (Nymphoides cristata, N. peltata) as targets for biological control in the United States

“…First, the geographic source of introduced populations must be located (Goolsby et al 2006). This is commonly done through molecular matching techniques in which plant tissues from introduced populations are sampled, their DNA is extracted and analyzed, then compared with samples from native populations (Williams et al 2018). This approach is especially important when the species have large geographic ranges because control agents may be locally adapted to a particular plant genotype (Boughton andPemberton 2011, Mukwevho et al 2017).…”