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Reproductive and Somatic Effort in Dogwoods. What is life history?. Grasses. Trees. vs. fast growth. slow growth. quick repro. delayed repro. An organism’s typical pattern of : Growth & Survival Reproduction. Components of Life History. SOMATIC effort E for growth/survival.
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What is life history? Grasses Trees vs. fast growth slow growth quick repro delayed repro • An organism’s typical pattern of : • Growth & Survival • Reproduction
Components of Life History • SOMATIC effort • E for growth/survival • REPRODUCTIVE effort • E for reproduction TOTAL ENERGY All organisms have limited energy; they allocate some energy to somatic effort & some to reproductive effort somatic & reproductive effort = trade-off
Purpose SOMATIC REPRO vs. LEAF buds FLOWER buds • HOW do dogwood trees allocate their energy to SOMATIC and REPRODUCTIVE efforts? • Examine 3 theories on life history trade-off.
Theory 1. Phenotypic plasticity 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 2. Sunlight affects reproductive effort Phenotypic Plasticity • Trees with greater annual energy available will have greater reproduction.
Theory 3. Age affects reproduction Age & Reproduction • All organisms need time for development before they begin to reproduce (mature)
Field methods Groups of 4 or 5 Go 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) Both Flower buds (reproductive) Leaf bud (somatic)
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 Terminal bud Opposite leaf scars Dogwood leaf scars are opposite, small, and encircle twig. Example of alternate leaf scars
Dogwood Identification Fruit: bright red, in clusters (late summer, fall) Flowers: white, four petals (spring) Leaves: opposite, veins curved