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Ecology and Biology of Melaleuca quinquenervia
Cheryl McCormick-RoteCenter for Aquatic and Invasive Plants
UF-IFASGainesville, Florida 32653
Background
Native range and introduction history
Distribution in FL (and beyond)
Native Range – NE Australia Host Range – South of Okeechobee
Regulatory status
About Melaleuca
Related to “tea tree oil” species, M. alternifolia
Large, evergreen tree up to 100’ tall
Large tap root (similar to a carrot)
Success in FL attributed to “climate matching”
Seasonal Patterns Flowers produced w/in 1 yr of germination
Year-round; mostly fall-winter (Oct-March)
Individual trees flower up to five times per year
New Shoot growth
Begins in mid winter; extends into spring
Plant Mating Systems – “Monecious”
Self-compatible & out-crossing; insect pollinated
Seed Production
Massive seed production
30-70 seed capsules/twig
Average 264 seeds/capsule
Over 500,000 seeds/twig/year!
Why is this significant?
3x more than native range
Contributes to rapid colonization
High germination
Release triggered by fire/girdling/stem damage
Seed Dispersal
No adaptations to facilitate seed dispersalHigh germination of seeds floating – long distance
Most fall close to parent tree – short distance
Wind – Almost all disperse no farther than ~ 500’
Hurricane-force winds: ~ 11 miles
No animal vectors (birds – exception?)
Seeds Everywhere…Continuous, light seed rain Mature stand: bi-weekly rain = ~2300 seeds/m2
Aerial seed bank estimates: 100 million seeds!
15% embryos 62% viable 75% germinate
~ 7 million germinated = lots of saplings!
High percentage of dormant seeds
Germination Saturated soil (w/in 3 days)
Optimum in full sun, but not required
Can germinate underwater on soil
Favors “Noisy hydroperiods” & wet conditions
Habitat Requirements
Climate Warm, but tolerates infrequent frost Survived severe freeze in Jan. 1977
Soils Flooded, saturated, and well-drained; also always or never flooded soils Acid sand, organic soils, alkaline marl, limestone Saline tolerant Low nutrient soils – deep tap root
Invaded Communities
Virtually south FL upland/wetland communities Undisturbed pine flatwoods, disturbed sites,
sawgrass marshes, cypress swamps, savannahs, mangroves, and wet prairies.
Typically invades open-canopy forests, sparseecotones, wetlands, and fire-damaged forests
Xeric communities resistant, not immune
Dense hammock communities – too shady
Population Dynamics
MQ estab. in FL >> vigorous than in AUS No co-evolved natural enemies to check populations
High-frequency FL fires and low areas
+ human disturbance explosive growth!
MQ infests wet marsh: structure/richness PRE: Low structural diversity (grasses dominate)Initial: Savannah: temp. increase in both S/RPOST: Closed-canopy stand/sparse understory w/ low structural diversity and community richness.
Implications for Native Species
Competitive superiority for resources
Light: Dense stands inhibit understory dev.
Nutrients: Tap roots exploit nutrients at water table
Water: Same as above
Soil Properties: Decomposition rate change
Soil Fauna: Soil micro- and macroarthropod shift
Fire: Frequency and intensity changes
Wildlife: Foliage/biomass not utilized; birds roost