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