Ecological Niche

1. Ecological Niche • The role a certain species plays in an ecosystem • the sum total of a species’ use of the abiotic and biotic resources in its environment

2. Competitive exclusion principle No two species can occupy the same niche in the same location in the same period of time! “two species with similar requirements can not coexist in the same community; one species will inevitably harvest resources and reproduce more efficiently, driving the other species to extinction”

3. Experiment that demonstrates competitive exclusion

4. This leads to the idea of the Ecological Niche Ecological Niche has two components: Fundamental niche – set of resources a population is theoretically capable of using Realized niche – the resources a population actually uses

5. Fundamental niche Species A

6. F G Realized niche Species A E B D C Ex.

8. Broad and Narrow Niches • Generalist species • Specialist species

9. Niches of Specialist and Generalist Species Which of the species you observed on Friday would you classify as generalist? Specialist? Specialist species with a narrow niche Generalist species with a broad niche Niche separation Number of individuals Niche breadth Region of niche overlap Resource use

10. Types of Species • Native species normally live and thrive in a particular ecosystem • Nonnative species are introduced - can be called exotic or alien or invasive

11. Nonnative Species • Nonnative plant species are invading the nation's parks at an alarming rate, displacing native vegetation and threatening the wildlife that depend on them • At some, such as Sleeping Bear Dunes National Lakeshore in Michigan, as much as 23 percent of the ground is covered with alien species, and the rate of expansion is increasing dramatically.

12. Invasive species in King County • Many noxious weeds are so widespread in King County that eradicating them is nearly impossible • Weeds include: yellow-flag iris, reed canarygrass, Scotchbroom, Himalayan and evergreen blackberry, English and Irish ivy, and purple loosestrife.

13. Indicator Species • a species whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem • reflect the quality and changes in environmental conditions as well as aspects of community composition

14. Examples of Indicator Species • Spotted owls – old growth forests • River otters – clean rivers • Frogs – pollutants transfer easily through skin • Corals – marine environments • http://www.thefutureschannel.com/dockets/insights/indicator_species/

15. Would Indicator species be considered generalists or specialists?

16. Keystone Species • a species on which the persistence of a large number of other species in the ecosystem depends. • If a keystone species is removed from a system • the species it supported will also disappear • other dependent species will also disappear • Examples • top carnivores that keep prey in check • large herbivores that shape the habitat in which other species live • important plants that support particular insect species that are prey for birds • bats that disperse the seeds of plants

17. Keystone cont. • exerts an impact on its community that is both strong and disproportionate to its abundance The sea star Pisasterochraceus, the original keystone species, feeds preferentially on mussels on northeast Pacific rocky shores. By doing so, the predatory sea star prevents mussels from taking over the entire shore and allows less competitive species to persist, thus enhancing local species diversity. (Source: Multi-Agency Rocky Intertidal Network) The sea otter Enhydralutris can be considered a keystone predator because its voracious feeding on herbivorous sea urchins allows kelps to flourish along the rocky coast, along with an entire ecosystem associated with these large marine plants. Photo by Matt Knoth. (Source: Wikimedia Commons)