Species Interactions

Species Interactions

Niche Definition: the role of a species within an ecosystem Not just the habitat, but how it interacts with other organisms, too

Types of Species Interactions • See figure 10, p. 204 • Competition • Predation • Symbiosis: • Parasitism • Mutualism • Commensalism

Competition Definition: when two or more individuals or populations try to use the same limited resource Both are negatively affected by the interaction

Types of competition • Interspecific competition – competition between members of different species Example: plants compete for limited nutrients in the soil around them, light, water, space, etc.

Interspecific Competition • Plant Competition Study by a professor at the Univ. of Wisconsin • How do plants compete in terrestrial communities? We know that plants compete for resources in most terrestrial ecosystems; however, a less obvious issue is whether plants compete more for above-ground resources (primarily light) or for below-ground resources (water and nutrients)? The answer to this question depends on the most limiting resource in any particular environment. For example, plants in many grasslands, where light is abundant, are probably competing more for below-ground resources than for light. In forests, however, light is very low in the understory, and thus plants in these systems are thought to be light limited. • We are investigating the relative importance of above- versus below-ground competition between plants in tropical forests. Currently, our studies involve liana versus tree competition; I am interested in expanding this work to include liana versus liana and tree versus tree competition.

The Community Ecology of Lianas • How do lianas add to forest dynamics, diversity, and complexity? Lianas (woody vines) are an abundant and diverse group of plants in forests throughout the world, particularly in the tropics. Lianas play a vital role in many aspects of forest dynamics, including contributing substantially to the overall species diversity in tropical forests, suppressing tree regeneration, increasing tree mortality, providing a valuable food source for animals, and physically linking trees together, thereby providing canopy-to-canopy access for arboreal animals (see papers listed below - Schnitzer and Bonger 2002 provides the best general overview).

Interspecific competition Organisms have different adaptations to improve competitive edge Produce many offspring, have extensive root systems that are efficient, some grow extremely fast Allelopathy – when a plant produces a chemical that prevents other plants from growing around it (black walnut, sunflowers, junipers)

Interspecific competition Example: warblers – different species of small songbirds that are similar in habit, compete for the same resources in trees Bay-breasted warbler Yellow-rumped warbler Cape May warbler

Niche partitioning Reduces interspecific competition by spatially dividing up resources

Niche partitioning Due to competition, each species uses less of the niche than they are capable of using Example: barnacles on p. 205

Types of competition • Intraspecific competition – members of the same species compete for food, mates, nesting sites, space, water, etc. Example: Wolves fighting for meat Alpha male will eat first

Intraspecific competition can also be called “survival of the fittest” and is a driving force of evolution The individual that is best adapted to outcompete the others will survive and pass on its traits to its offspring

Predation Type of species interaction in which one organism (predator) feeds on another (prey)

Predator/Prey relationships Does the predator control the prey, or does the prey control the predator?

Predator/Prey relationships Adaptations that have evolved due to predator/prey relationships: Camouflage – organism blends in with environment - studies show that animals recognize other animals by three main features: guess?

Camouflage Recognize other animals by • Eyes • Silhouette – ex: goslings responded to shadow shapes in different ways • Body’s bulk Most forms of camouflage disguise one of these features .

Butterfly with fake eyes on wings

Butterfly that resembles a dead leaf

Warning Coloration Bright colors advertise the fact that a prey is distasteful or poisonous Ex: bees, poison arrow frogs, coral snake

Mimicry Batesian mimicry – when one palatable species mimics another that is harmful or distasteful Ex: insects mimic wasps Right: A and B are stinging wasps, C-E are flies that mimic the wasps, F is a beetle that mimics the wasps

Batesian mimicry – moth resembles spider

Mimicry Mullerian mimicry – when two or more species look alike and both are unpalatable, both benefit from the reinforcement to predators to avoid the pattern seen Ex: Viceroy and Monarch are BOTH unpalatable Monarch Viceroy

Urban mimicry http://www.worth1000.com/contest.asp?contest_id=9307&display=photoshop

Species Interactions