8-2 Types of Species

What Roles Do Various Species Play in Communities? A Biological Play with Many Part

Ecologists often use labels—such as native, non-native, indicator, keystone, or foundation—to describe the major ecological roles or niches various species play in communities.

Native species are those that normally live and thrive in a particular community. Others that evolve somewhere else and then migrate into or are deliberately or accidentally introduced into a community are called non-native (or exotic) species, invasive species, or alien species.

What Are Indicator Species? Living Clues to Environmental Conditions

Some species provide excellent clues to key environmental conditions, and they are considered to be indicator species for their environment.

For example, the presence or absence of trout species in water within their range of tolerance is an indicator of water quality because trout need clean water with high levels of dissolved oxygen. Additionally, certain species of stoneflies, mayflies, caddisflies, seed shrimps, snails, and other aquatic invertebrates are used as indicators of water quality in streams and rivers.

Case Study: Why Are Amphibians Vanishing? Warnings from Frogs

Frogs are good indicator species of environmental quality and pollution because they are especially vulnerable to disruption at various points in their life cycle. Since 1980, hundreds of the world’s estimated 6 300 amphibian species have been vanishing or declining in almost every part of the world, and several factors have been thought as to why:

  • Habitat loss and fragmentation, especially because of the draining and filling of inland wetlands, deforestation, and development.

  • Prolonged drought, which dries up breeding pools so that few tadpoles survive.

  • Pollution can also play a role. Frog eggs, tadpoles, and adults are very sensitive to many pollutants, including insecticides, herbicides, fertilizers, and endocrine disruptors.

There are 3 reasons why we should care about the declining frog population:

  1. It suggests that environmental quality is deteriorating in parts of the world because amphibians are sensitive biological indicators of changes in environmental conditions

  2. Adult amphibians play important ecological roles in biological communities.

  3. From a human perspective, amphibians rep- resent a genetic storehouse of pharmaceutical products waiting to be discovered.

What Are Keystone Species? Major Players Who Help Keep Ecosystems Running Smoothly

A keystone is the wedge-shaped stone placed at the top of a stone archway. Remove this stone and the arch collapses. In some communities, certain species called keystone species play a similar role.

Originally, ecologists focused on top predator keystone species that feed on and help regulate populations of other species. Eventually, ecologists realized that other roles could have a crucial impact. One such role is pollination of flowering plants by bees, humming- birds, bats, and other species.

The loss of a keystone species can lead to population crashes and extinctions of other species in a community that depend on it for certain services.

What Are Foundation Species? Players Who Create New Habitats and Niche

Some ecologists use the term foundation species to refer to those keystone species that play a major role in shaping communities by creating and enhancing habitat that benefits other species.