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Reproductive and Somatic Effort in Dogwoods
What is life history?• An organism’s typical pattern of :
– Growth & Survival– Reproduction
Grasses Trees
fast growth
quick repro
slow growth
delayed repro
vs.
All organisms have limited energy; they allocate some energy to somatic effort & some to reproductive effort
somatic & reproductive effort = trade-off
Components of Life History
TOTAL ENERGY
SOMATIC effort• E for growth/survival
REPRODUCTIVE effort• E for reproduction
Purpose HOW do dogwood trees allocate
their energy to SOMATIC and REPRODUCTIVE efforts?
Examine 3 theories on life history trade-off.
SOMATIC REPRO
LEAF buds FLOWER buds
vs.
Phenotypic Plasticity• A single organism can have >1
phenotype• Depending on environment, 1 tree can
have multiple life history patterns (differences in SOMATIC and REPRO effort within one tree)
Theory 1. Phenotypic plasticity
Phenotypic Plasticity• Trees with greater annual energy
available will have greater reproduction.
Theory 2. Sunlight affects reproductive effort
Age & Reproduction
• All organisms need time for development before they begin to reproduce (mature)
Theory 3. Age affects reproduction
Field methodsGroups of 4 or 5Go to either sunny or shady site (as
assigned) and survey 20 trees.1) Record number of leaf buds and flower buds per 40 buds on each tree. If you’re in the roadside environment, you’ll do 20 on the sunny side and 20 on the shady side. Data sheet is on page 37.2) Measure the DBH (cm) of each tree trunk.
Dogwood Identification (Winter)
Flower buds(reproductive)
Leaf bud(somatic)
Both
Bark: dark brown with squarish, scaly blocks.
Young trees will be smooth and not as distinctive.
Terminal Buds
Examples of different numbers of bud scales
Dogwood with two bud scales. Twigs are slender, green or purple.
Leaf Scars
Dogwood leaf scars are opposite, small, and encircle twig.
Example of alternate leaf scars
Opposite leaf scars
Terminal bud
Dogwood Identification
Flowers: white, four petals (spring)
Fruit: bright red, in clusters (late summer, fall)
Leaves: opposite, veins curved