The Galapagos Flora

Vascular flora – 863 species
    - 749 species are angiosperms
    - 216 are endemic to the Galapagos Islands
    -7 flowering plant groups
        - Darwiniothamnus, Lecocarpus, Macraea, Scalesia (family Asteraceae)
             - Scalasia - best example of adaptive radiation (animal or plant group adapts to a variety of habitats and evolves into new entities)
        - Brachycereus, Jasminocereus (Cactaceae)
        - Sicyocaulis (Cucurbitaceae)
    - 271 species are natives
          - Colonized the Galapagos Islands by natural means
          - about 90% originated in western South America
    - 262 species are exotic
          - Present as a result of humans coming to the islands

How the flowers arrive
    Exotics – result of human contact
    Native plants and ancestors of endemics – result of long distance dispersal
        - Birds carry seeds
        - Fruits and seeds have adhesion, so it sticks to feathers or feet of birds
    Coastal plants – arrive on ocean currents
    Seeds may possess wings or plumes that allow them to be caught in a passing breeze

Vegetation Zones
    - Littoral (Coastal Zone)
       - Occupies shoreline, varies in composition from lava boulders to sandy beaches
       - Plants must be capable of surviving in a salt-rich environment that may be covered with water during certain periods of the day but exposed at others
       - Layer of salt present on upper surface of the leaves
       - Most plants inhabiting zone are not endemic
    - Arid Zone
       - Extremely dry during most of the year, most plants are deciduous
       - Shrubs, Cactus very common
    - Transition Zone
       - Both deciduous and evergreen trees
       - Many shrub and herb layers
       - Hardest zone to pinpoint because of few dominant indicator species
    - Scalesia Zone
       - Dominated by evergreen tree
       - Shrubs common, not densely packed
    - Zanthoxylum Zone
       - Dominated by small evergreen trees
       - Shrubs and herbs abundant
    - Miconia Zone
       - Located on San Cristobal and Santa Cruz (not applicable to our islands)
    - Fern-Sedge (Pampa) Zone
       - Mostly club mosses, ferns, sedges, grasses
       - No trees located in zone before arrival of humans

Threats to Vegetation
    - Introduced Animals
       - Domesticated animals and plants
          - Pigs, goats, burros, cattle
       - Some animals referred to as feral (animals roam about at will and eventually become wild)
          1. Movements trample and wear trails through vegetation
          2. Each of the animals feed primarily on plants
       - Attempted solutions
          - Enclosures, fences
       - 1950s - Fishermen released goats on Pinta
          - Goats thrived and reproduced, plant life was devastated
       - Cottony cushion scale - Insect causing damage
          - Infects plants, making them sickly and they frequently die
    - Exotic Plants (438 species)
       - 26% of exotic plants are introduced weeds
       - Many plants brought to be cultivated for food
       - About 50% are of little concern - not competing with endemic and native members of flora

From: McMullen, Conley K. Flowering Plants of the Galapagos Cornell University Press (1999,

South Korea

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Current Events

The blackberry is one of the most aggressive and most out of control plants on the island.
- The thorny plant is crowding out native flora by soaking up nutrients in the soil, sunlight, and water
- Blackberries were introduced by farmers about a decade ago

From: Otis, John. “Creatures no comfort to Galapagos isles; Fragile ecosystem overrun by tourists, other alien species.” The Houston Chronicle. (17 April 2004, Sec. A, p 1).

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