Wendy Scholl Invasion Ecology Swollen Bladderwort Scientific name: Order/Family/Genus/Species Scrophulariales/ Lentibulariaceae/ Utricularia L./ Ultricularia inflatalU. infiata waiter Common Names: Swollen Bladderwort, Floating Bladderwort, Large Floating Bladderwort, Inflated Biadderwort. 1 Overview: Swollen Bladderwort is a known invasive species in the state of Washington. Introduced to Western Washington in the early 1980’s the plant is now found in at least 5 counties. At this time it’s method of introduction is unknown. Utricularia inflata’s close resemblance to other native bladderworts is problematic in that it presents the possibility that we may have a larger invasive population than we currently realize. A beautiful and fascinating species, it is known to be endangered in some of its home ranges. That, however, does not prevent it from posing a significant threat to some of our own native populations offlora and fauna in addition to possibly serious financial costs should its local range increase. While U. infiata is, as far as we know, limited to a handful oflocations in Western Washington at this time, there is a disturbing lack of any effort to eradicate the population while it remains small. Key features: Basic features for Utricularia inflata are: A. Lacy underwater foliage with seed-like bladders B. Yellow snapdragon-like flowers C. Spoke-like structure supporting the flower stalk Utricularia inflata is differentiated from other bladderworts, especially Utricularia radiata, based on these key features; The lateral foliar units (leaves), floats, vernation (the arrangement of young leaves in a bud) of the branch tips, the inflorescence bracts, flowers, peduncle lengths, orientation of the fruiting pedicel, character correlation (obtained by plotting flower number against peduncle length), and distribution (Reinert et al. 1962). (FIG 1.) 2 .I4 VI, 49 r 1 - - - - 1 /.-7i 4 - I -“I )i j FIG. 1; Key describing distinguishing features of Utricularia inflata; Courtesy of The American Journal of Botany. 3 Life History and basic ecology: Swollen Bladderwort is a free-floating perennial herb; rootless, carnivorous, and aquatic, it uses “seeds” or bladders to capture prey. The stem and flowers are supported by a wheel or spoke-like structure with lacy, finely divided and haired underwater foliage. The stem can vary from six inches to two meters long and while usually emergent, can be either partly supported by exposed sediment, submersed or floating.16 The emergent flowers are yellow and snap-dragon-like in appearance with a lower, banner-shaped petal. They occur in groups of 3 to 14 on the upright 14 4 plant stems. In swollen Bladderwort the seed stalk can be up to 35 mm long.’ The has no true leaves. Although often referred to as leaves, that functional purpose is served by the bladder-bearing, chiorophyllous laterals. As shoots terminating in tubers do originate from these structures under certain conditions2, Reinert (1962) felt that they are more likely stem structures (Remert et al. 1962; Farooq Ct al. 1966). The float can appear dense and bushy underwater and has anywhere from 4 to 10 4 and are slender at the base, spokes5. The spokes themselves vary from 4 to 9 cm.’ widening in the middle and then tapering again at the terminal end. U. injiata reproduces from seeds, fragments, tubers, and small coiled winter buds, 2 Turions are tightly packed, ball-shaped groups concave also called turions of leaves covered in protective mucus. These are heavy with starches and sink to the bottom of the water column where they remain dormant in the sediment for the winter’0. The tubers of U inflata are produced when the plant becomes stranded on sediments due to low water. The plant sends out thin, thread-like shoots that terminate in tiny, starch-filled tubers. While the thin shoots can be produced during periods when the water levels drop and the water becomes stagnant, the tubers themselves are only produced when the plant actually becomes embedded in the benthic deposits (Reinert et al. 1962). Reinert also states in his 1962 paper that while they never saw these tubers result in germination in the field they did so easily when submersed in water in the laboratory. Related to it’s ability to reproduce from fragments, it has also been observed that at the end of the fruiting season the older ‘6lnternet Publication/Online Document; www.aquariumarticles.com 2 Internet Publication/Online Document; Washington State Department of Ecology 5lnternet Publication/Online Document; Massachusetts Department of Conservation and Recreation. ‘4lnternet Publication/Online Document; Washington State Department of Ecology ‘° Internet Publication/Online Document; Botanical Society of America. 4 parts of the plant appear to decay and the branch tips separate, remaining dormant until the next growing season. Swollen Bladderwort is, as stated earlier, carnivorous and obtains nutrients via photosynthesis, absorbing nutrients from the water column and by consuming tiny fish it captures in 5 The bladders are, in invertebrates and minute that its bladders. fact, traps and use a vacuum4ike suction to pull prey inside after the prey has triggered the bladders “trap door”.2 The animals are attracted to the bladders by way 5 or mucus and open the trap doors by coming into contact with of a sweet “scent” trigger hairs. Enzymes and bacteria digest the animal once it has died inside the bladder. The bladders of carnivorous Utricularia species are 10% - 50% of the total biomass of the plant (Adamec, 2006). When mature the bladders are approximately 3 mm. long (Reinert et al. 1962). FIG.2 Close-up of Utricularia inflata bladder showing trigger hairs. Courtesy of The Nature Conservancy. 2 Internet Publication/Online Document; Washington State Department of Ecology Internet Publication/Online Document. Massachusetts Department of Conservation and Recreation 5 Due to their ability to capture live prey, they are able to flourish in both oligotrophic 5. This, combined with their tolerance for a wide range of as well as eutrophic lakes water chemistry conditions, gives them a competitive edge over many native plants. Optimal conditions for aquatic bladderwort species are warm, shallow, www.BestC ; i I I 7’ FIG.3 Utricularia inflata stems and bladders oligotrophic 5 tolerances waters that are oxygen deficient. Acidity can vary with some species doing well in more acidic waters and others requiring a high pH. (Dite et al. 2006). It prefers slow moving and still waters and can create dense mats that shade out native vegetation. It’s wide range oftolerances and ability to utilize resources gives it advantages in the unlikeliest of locations. In at least one documented instance it was located in an unnamed drainage pond beside a highway in Thurston Internet Publication/Online Document; Massachusetts Department of Conservation and Recreation. 6 County, Washington, not a site likely visited by recreational boaters or aquaria enthusiasts. Bladderworts in their native ranges provide important food, habitat, and protection for fish and aquatic invertebrates. Waterfowl and another highly invasive species, the muskrat, also consume them. Although it flowers during the winter in its native 2 When not in flower range it flowers much later, from June to July, in Washington. it is difficult to distinguish from our native bladderworts but when in flower, is distinguished by its spoke-like float. According to the Washington State Department of Ecology, swollen bladderwort, when not in flower, may be easily confused for other, smaller native blaclderworts as well as water milfoils (Myriophyllum spp.) and White water buttercup (Ranunculus aquatiis). Origin and Distribution: There seems to be some confusion over the total number ofbladderwort species, with Reinert (1962) listing 300 and the American Botanical Society listing 220. Published information indicates that approximately 30 are aquatic. In addition there is little consensus on the native distribution with the general observation being the eastern coastal plains of the United States. Bladderworts have dispersed across the globe and are native to nearly all ecosystems from Australia to Alaska (Reinert et al. 1962). Approximately 20 species are endemic to the United States and U infiata is now known to be present in Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, New Jersey, North Carolina, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and Washington. Native distribution is reported as occurring on the outer coastal plain from Texas and Alabama to Delaware (Reinert et al. 1962; Urban et al. 2006). It has been reported that U inflata had spread as far north as New York and Massachusetts by the early 1990’s (Urban et al. 2006; Mitchell et al. 1994). Although the plant is native to warmer southern waters it has been shown to be capable of survival in colder climates and is able to survive the winter in frozen lakes. 2 Internet Publication/Online Document; Washington State Department of Ecology Internet Publication/Online Document; Massachusetts Department of Conservation and Recreation. 7 %PLANTS IJaska I IDistrict ofCoIurn I IHawii I I IPuertoRioD I\rin Islands I FIG.4 Map showing current United States distribution of Utricularia inflata. Courtesy of the USDA. FIG.5 Map showing known occurrences of Utricularia inflata in the state of Washington. Courtesy of Kathy Hamel, Washington State Department of Ecology. 8 The plant’s history of mvasiveness is equally as difficult