Angiosperm Evolution - Pollination Syndrome

Evolution

Oldest Angiosperm Fossil (145 m.y.a), identified through fossilized pollen grains.

  • ex. Archae fructose - a complete plant fossil found later, shows primitive structures (no petals + sepals).

Diversification

Albian Period (113 m.y.a) - in the middle of the Cretaceous Period, is where significant diversification occurred. Advantages of flowering plants include:

  1. Promoting Outcrossing by attracting pollinators → more genetic diversity.

  2. Vessels and Tracheid’s for enhanced water and material transport.

  3. A Rapid Life Cycle w/ some species capable of flowering and setting seeds in a day.

    • These adaptions allow Angiosperms to thrive and dominate during the Cretaceous period.

Trends

Basal → Magnoliids → Monocot → Eudicots

  • Some species remain unchanged throughout time like the Basal Angiosperms, Water Lilles (Nymphales)

  1. Many flowers parts → Fewer flower parts

  2. Superior Ovary’s → Inferior Ovary’s (for better protection)

  3. Formation of Corolla resulting in Zygomorphic Flowers (increased pollinator attraction)

Pollination Syndrome

Plants aim for Outcrossing (cross-breeding w/ other plants), rather than self fertilization which reduce genetic variety and susceptibility to disease.

  • Pollinator Needs

    • Nectar

    • Colorful Petals

    • Scent

    • Landing Structures

  • Pollinators + Flowers

    • Beetles: Scented and open flowers

    • Bee: Like blue + yellow, tubular flowers for nectar collection

    • Butterflies: Tubular and colorful flowers

    • Hawkmoth: No color necessary or landing pad (hover), nectar’s a must, Flower opens at night

    • Hummingbird: No landing pad (hovers), nectar’s a must

    • Bat: Larger flower or inflorescence, higher pollen production, no colorful petal.

Colors in Flowers

pigments for pollinator or from stress (Autumn chlorophyll breakdown)

Inside the Flavonoids group there are Anthocyanins the have the red, blue and purple hues.

  • Acidic Environments = Blue

  • Basic Environments = Red

Flavanols: Colorless, Blocks UV light

Betacyanin: (hot pink + red)

  • No Anthocyanin

  • Alkaloid compound

Carentenoids: (Yellowish)

  • Hydrophobic in the their chloroplast

  • Bees see it as purple → shows pollinator target