GEOL388
6-17-08

The terrestrial community



John Merck

Energy flow: Yesterday we neglected a major ecological topic - the flow of energy within an ecosystem. To address this, we need to consider more than just plants, although they are an essential component for it is they who capture the energy of sunlight, by means of photosynthesis, and make it available to other organisms. We think of energy flow in terms of:

For the purposes of our presentation, the terrestrial commnity consists of land plants and all of the critters that get their energy from them. Thus, for the moment, creatures like sea birds and marine iguanas don't count, even though they often hang out on land. Emphasizing this disconnect is the fact that climatic episodes like El Niño effect the marine and land realms differently.

Jackson organizes the major members of the terrestrial ecosystem into a food web. Below is my embellished version:

A couple of comments:

A brief orientation to the more familiar land animals:

Primary consumers

Insects: As anywhere, there is a great diversity, but not so many that a person can't keep track of the important ones. Many of the conspicuous herbivorous insects are nectar-feeding pollinators:

  • Carpenter bee: (Endemic) Solitary and sexually dimorphic with indigo-black females and yellow-brown males.

  • Lepidoptera: Moths and butterflies - Originally thought to contain seven endemic species, which resemble mainland relatives. More recent surveys have turned up twelve, several of which are poorly studied. You're very likely to see:

  • Orthoptera: Grasshoppers and katydids - The Galápagos boast the most beautiful grasshopper in the world, the painted locust (Endemic). These beefy insects are a major food source for lava lizards.

  • Others: Various beetles and true bugs. One odd insect of note is a recently introduced exotic, the Cottony cushion scale, which is attacking native plants and appears to have no natural predators.


Painted locust Schistocera melanocera

Reptiles: We have two lizards and the tortoise: