Land of Many Opportunists
OverviewStudents will learn how aggressive exotic species take advantage of a wide range of resources in order to expand their range and compete in a nonnative habitat.
Students will learn how aggressive exotic species take advantage of a wide range of resources in order to expand their range and compete in a nonnative habitat.
Many exotic species can easily take advantage of a wide range of required resources (water, food, shelter, space, etc.), because they are living in an ecosystem that is not their native one. Exotic animals may feed off of a broad range of foods and have no native predators existing to control their populations. Invasive exotic plants may be successful in a variety of soils and environmental conditions. Exotic plants and animals may not be affected by native diseases, which normally act in the ecosystem to regulate and maintain normal populations. Ecologists consider any species that can take advantage of a broad spectrum of resources opportunistic.
On the other hand, sensitive native species tend to have evolved very specific environmental needs. This makes survival
difficult when unexpected changes-biological or environmental-occur. An example of a highly specialized native species is an alpine plant. If the climate gets slightly warmer, trees take over the habitat. If the climate gets colder, rock and ice begin to dominate. When nonnative species move into a habitat, they can modify and impact the ecosystems they invade. Those native species with specific habitat requirements may lose their ability to compete with opportunistic intruders.
If the exotic species is highly aggressive, it may even be able to create a monoculture and keep native species from re-colonizing the habitat. Fortunately for the natives, nature has built-in regulatory systems which make monocultures extremely unstable in the natural world. Agricultural researchers are continuously battling this natural 'regulatory system' with pesticides, because their own monocultures of agricultural plants are so often under relentless attack by disease. So it is possible that through nature's tendency to balance itself out, a natural 'remedy' would develop against invasive monocultures to keep exotics at bay.
Explore Great Sand Dunes' web page on plants for more on the many flowering plants of the park and preserve.
Pinto beans, red beans, black beans, 60 feet of rope, 6 boundary cones, clipboard, graph paper
In this relay game of tag there are four teams: red bean, black bean, pinto bean, and invasive (exotic). The goal of each team is to gather as many of their resources (beans) as they can and make a pile at their team's cone.The course is laid out with a ten-foot diameter rope circle in the center. About 100 beans of each type are scattered in the circle. Four team cones or home base makers are set equidistant around the circle, about fifteen feet from the rope's edge.
Each of the five or more game sessions lasts for only three minutes. After each session, the bean count for each team will be graphed on graph paper and all the beans will be re-scattered into the center of the circle. The team with the least number of beans after each session will be required to move their cone ten feet farther away from the circle, representing the weakening of a population due to strengthening competitors. (If the team that moved ten feet back in a previous session collects the most beans during subsequent sessions, they may return their cone to its previous position.)
The first session begins by establishing a baseline. Only the three bean teams will compete. One student per team will run to the rope enclosure and collect five of their team's bean resources (pintos are collected by the pinto team, reds by the red team, etc.), return to their cone, and place the beans in a pile next to the cone.
Then the next member of their team will be allowed to go and collect beans. When the three minutes are up, the game will be stopped and beans will be counted and graphed. Team members that are not actively collecting beans must be touching their team's cone.
The second session is played similarly to the first, with the addition of the invasive team. Since the members of the invasive team are opportunists, they may collect up to ten beans of any color with each member's turn to go to the circle.
The third and fourth session are played identically to the second. Remember to move the cone of the team with the least beans back ten feet after each session.
In the fifth session, the invasive team is allowed to be an 'aggressive' invasive species (without being physically or verbally aggressive). When they approach the center, they can either collect beans or acquire another person's beans by tagging someone within the circle.
At the end of the game, discuss the outcomes which are visually displayed on the graph. With older students, be sure to discuss these questions:
- Native species usually play an important role in supporting their ecosystem. Since the reds, blacks, and pintos have been reduced in numbers and are not able to play their supporting role in the local ecology, how will the invasive species cope with a weakening ecosystem?
- It is usually the case in ecosystems that a consumer actually plays a role in supporting the producer on which it depends.
A) What may happen to the populations of native producers (beans) when their biological consumers/supporters (students) diminish in population? And since invasive species have not evolved naturally in conjunction with the native producers,
B) will the invasive species be able to support the native producers or will they destroy the integrity of the resources on which they have become dependent?
- What might happen to the invasive species if it becomes a monoculture and entirely displaces the native consumers?
Look at the Exotic Escapes online activity.