Community EcologyCommunity EcologySpecies Interaction

“Just as populations contain interacting members of a single species, communities contain interacting populations of many species.” – Holt Modern Biology – Ch 20

Probably the most interesting predatory aspects is that of the Lizardfish / Goby interaction. The lizardfish that prey on gobies are not much larger than the food they eat. In fact, a 5 cm lizardfish can eat a 3 cm Hawaiian Shrimp Goby!

Predation

In predation, an individual of one species, called the predator, eats all or part of an individual of another species, called the prey.

Many types of organisms can act as predators or prey.

A predator’s survival depends on its ability to capture food, but prey’s survival depends on its ability to avoid being captured.

• The predator species (in the illustration below, the Lion (Panthera leo) kills and consumes the prey species (in this case, a Cape Buffalo (Syncerus caffer).

Linx chasing Hare

• Lady bug (“ladybird beetle”) preying on an aphid.

sundew carnivorous plant•

Plants cannot run away from a predator, but many plants have evolved adaptations that protect them from being eaten.

Physical defenses such as sharp thorns, spines, sticky hairs, and tough leaves can make plants more difficult to eat.

Competition Interspecific competition is a type of interaction in

which two or more species use the same limited resource. For Example, both lions and hyenas compete for prey such as zebras.

Both lose!

If two species compete for a resource, the result may be a reduction in the number of either species or the elimination of one of them.

More often, one species will be able to use a resource more efficiently than the other. As a result, less of the resource will be available to the other species.

Competition – Anole lizards• The Green Anole (Anolis carolinensis)

is native to the southern United States. In the 1960's, The Brown Anole (Anolis sagrei) was introduced from Cuba.

• The two species vie for habitat and food resources, and it appears that the exotic Brown Anole has displaced the native Green Anole in some physical spaces, such as lower shrubbery and grass.

• The Green Anole generally lives higher up in the trees and foliage than the Brown Anole does. This result of competition is known as resource partitioning.

Symbiosis

A symbiosis is a close, long-term relationship between two organisms.

Three examples include:

• parasitism

• mutualism

• and commensalism

Parasitism• Parasitism is similar to predation in that

one organism, called the host, is harmed and the other organism, called the parasite, benefits

tapeworm

ascarus

The Human Head Louse

Mutualism Mutualism is a relationship in which two species

benefit from each other.

Some of these relationships are so close, that neither species can survive without the other. (It is sometimes called obligate mutualism - Ex:termite and trichonympha)

• The Clown Fish and its Sea Anemone partner both benefit from the relationship: The fish gets a safe home that protects him from predators, and he fiercely protects his sea anemone. He also feeds the anemone. (It is also called Protocooperation because each can survive without the other.)

Nemo lives in an anemone.

Pollination is one of the most important mutualistic relationships on Earth.

Ants & Acatia Trees in Central America.

The ants live in the thorns and gain food from the acacia. The ants defend the acatia from insect herbivores.

Commensalism Commensalism is an interaction in which one

species benefits, and the other species is not affected. (from english “sharing of food” or from latin “sharing a table”)

Originally, the term was used to describe the use of waste food by second animals (scavengers), like the carcass eaters that follow hunting animals, but wait until they have finished their meal.

Cattle egrets eat insects and lizards that are forced out of hiding by the movement of Cape buffaloes in Tanzania. (The birds occasionally feed on ectoparasites on the

buffalo, but generally the buffalo do not benefit from the egrets)