Hydrilla verticillata: Biology and Ecology - PowerPoint PPT Presentation

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Hydrilla verticillata: Biology and Ecology

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Hydrilla reduces open water feeding and spawning areas of sport fish. Clog boat motors ... Nonindigenous aquatic and selected terrestrial species of Florida. ... – PowerPoint PPT presentation

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Title: Hydrilla verticillata: Biology and Ecology


1
Hydrilla verticillata Biology and Ecology
By Carey Minteer - University of Arkansas
2
Background
  • Native of southeast Asia
  • Introduced into the United States in 1955
  • Federal noxious weed
  • Since 1983 Hydrilla has been the most abundant
    submerged plant in Florida (McCann et al, 1996)

3
More Background
  • Plants can be monoecious or dioecious (Van
    Driesche, 2002)
  • Populations in the southeastern United States are
    dioecious and entirely female.
  • Plants spread through vegetative regeneration.
  • Monoecious strain found in Potomac river (Steward
    et al., 1984).

4
Monoecious strain
  • Spreading down the Potomac river.
  • Sexual reproduction can occur.
  • Pollination occurs on the waters surface
  • Pollen is released from free floating male
    flowers and caught by the free floating female
    flowers (Cronk and Fennessy,2001).

5
Vegetative reproduction
  • Subterranean tubers
  • Axillary turions
  • Fragments

6
Subterranean Tubers
  • Sometimes buried several centimeters below the
    surface.
  • Can sprout new shoots even after a period of 4
    years.
  • In Florida canal there are an average of 918
    turions per m-2 (Sutton, 1996).

Tim Murphy, University of Georgia, Bugwood.org
7
Axillary Turions
  • Turions form in the leaf axils at the ends of the
    stems.
  • Turions abscise and fall into the sediment.
  • Over winter and produce new growth in the spring.

8
Fragmentation
  • Spread from lake to lake by boats.
  • Large populations found adjacent to boat ramps.
  • Spreads extremely fast
  • Total lake coverage can change drastically in
    just a years time.

Raghavan Charudattan, University of Florida,
Bugwood.org
9
Biology
  • Monocot
  • Family Hydrocharitaceae
  • Rooted submerged perennial
  • Leaves 5-15 mm long and 2-4 mm wide
  • Leaves arranged in pairs on lower nodes.
  • Leaves in whorls of 3-10 on the upper nodes.

10
More Biology
  • Stems vary in length from a few centimeters to
    several meters.
  • Three types erect, horizontal, or subterranean.
  • Erect stems support branches, leaves, and flowers.

Chris Evans, River to River CWMA, Bugwood.org
11
Habitat
  • Sunny
  • Sandy substrate
  • Low levels of rock
  • Grows in depths between 0.7m and 2.4m
  • Has been shown to grow in depths of up to 15m.

Raghavan Charudattan, University of Florida,
Bugwood.org
12
Habit
  • Apical growth
  • Several erect stems form at a single node of a
    horizontal stem
  • Branches form a canopy
  • 70 of biomass concentrated at the waters
    surface (Cronk and Fennessey, 2001).

Carey Minteer, University of Arkansas
13
Distribution
http//www.eddmaps.org/distribution/subdist.cfm?su
b3028
14
Effects on Native Vegetation
  • Hydrilla forms lush canopies, that shades native
    vegetation.
  • Alters seed banks
  • Allelopathic
  • Shown to inhibit the growth of Ceratophyllum
    demersum (coontail) (Schmitz et al., 1993).

15
Effects on Animals
  • Dense stands provide refuge for young fish.
  • High survival rates leads to over population and
    stunted fish growth.
  • Predator fish cannot forage as well.
  • Numbers and biomass of these predatory fish
    decline.

16
Effects on Human Activities
  • Hydrilla reduces open water feeding and spawning
    areas of sport fish
  • Clog boat motors
  • Thick mats can hinder irrigation by as much as
    90 (CDFA,2000).
  • Hydroelectric power is hindered by fragmentation
    of plant material

Wilfredo Robles, Mississippi State University,
Bugwood.org
17
More to come
  • Control of Hydrilla
  • Biological, mechanical, chemical.

18
Literature Cited
  • California Department of Food and
    Agriculture.2000a. Hydrilla program 20.20.1,
    Program statement 2000 season, fiscal year
    200/2001. Plant Health and pest prevention
    services, Integrated pest control branch,
    Sacramento, CA.
  • Cronk, J. and M. Fennessy. 2001. Wetland plants.
    Biology and Ecology. CRC Press LLC, NY.
  • McCann, J.A,, Arkin, L.N., and Williams, J.P.
    1996. Nonindigenous aquatic and selected
    terrestrial species of Florida. Orlando,
    University of Florida, Center for aquatic plants
    website. http//aquat1/ifas.ufl.edu/mctitle.htm
  • Schmitz, D.C., Schardt, J.D., Leslie, A.J.,
    Dray, F.A., Osborne, J.A., and Nelson, B.V.1993.
    The ecological impact and management history of
    three invasive alien aquatic plant species in
    Florida. Biological pollution The control and
    impact of Invasive exotic species. B.N. McKnight,
    Ed. Pp 173-194. Indianapolis, Indiana Academy of
    Science.
  • Steward. K.K., Van, T.K., Carter,V., and
    Pieterse,A.H. 1984. Hydrilla invades Washington
    D.C. and the Potomac. American Journal of Botany
    71162-163.
  • Sutton, D.L. 1996. Depletion of turions and
    tubers of Hydrilla verticillata in the North
    River canal, Florida. Aquatic Botany53121-130.
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