Habitat & Niche Habitats and Niches June 4, 2018

Habitat place where an animal or plant lives where it gets food where it gets water type of environment in which a population or species regularly lives. physical and biotic environment vegetation Forest, meadow, pasture, coniferous forest, etc. Habitats and Niches June 4, 2018

Habitat Habitats may be subdivided into layers or zones Microhabitats Forest canopy: leaves, branches Shrub layer: leaves, branches, trunks Herb layer: leaves, stems, mosses, ferns Litter: dead fallen leaves, logs, Varies in depth, quality Soil: topsoil, subsoil Habitats and Niches June 4, 2018

What is the niche? set of conditions within which an organism can maintain a viable population total set of environmental factors that determines a species’ distribution. An organism’s role within a community. temperature light intensity okay salinity ecological niche Habitats and Niches June 4, 2018

Niche types (a) Fundamental niche: All resources that could be used in absence of competition. depends on physical (abiotic) conditions. Habitats and Niches June 4, 2018

Niche types (b) Realized niche: Resources actually used in presence of competitor. depends on biotic as well as abiotic conditions. Habitats and Niches June 4, 2018

Law of Competitive Exclusion No two species will occupy the same niche and compete for exactly the same resources for an extended period of time. When forced to compete, one will either migrate, become extinct, or partition the resource and utilize a sub-set of the same resource. Given resource can only be partitioned a finite number of times.

Law of Competitive Exclusion Habitats and Niches June 4, 2018

Resource partitioning Resource partitioning avoids competition; Realized niches divide resources among several species. Habitats and Niches June 4, 2018

Resource Partitioning

Keystone Species A species or group of species whose impact on its community or ecosystem is much larger and more influential than would be expected from mere abundance. Large predators Critical food organisms (bamboo and pandas) Often, many species are intricately interconnected so that it is difficult to tell which is the essential component.

Introduced Species If introduced species prey upon or compete more successfully than native populations, the nature of the community may be altered. Human history littered with examples of introducing exotic species to solve problems caused by previous introductions. Mongoose and Rats in Caribbean

Invasive species Invasive species competitively exclude native species: Imported fire ant Kudzu Purple loosestrife Zebra mussel Habitats and Niches June 4, 2018

Kudzu – Invasive & Exotic

Abundance and Diversity Abundance -Total number of organisms in a community. Diversity - Number of different species, ecological niches, or genetic variation. Abundance of a particular species often inversely related to community diversity. As general rule, diversity decreases and abundance within species increases when moving from the equator to the poles.

Edges and Boundaries Edge Effects - Important aspect of community structure is the boundary between one habitat and others. Ecotones - Boundaries between adjacent communities. Sharp boundaries - Closed communities Indistinct boundaries - Open communities