Lecture 5/6: measuring biodiversity (cont.)

gamma diversity

the rate of change of a species composition with respect to distance in a landscape, particularly at regional scales or larger. AKA the turnover rate of species with respect to distance between sites of similar habitat within the regional landscape

general global patterns of diversity

- all major classes of vertebrates and plants show increases in number closer to tropical latitudes (some exceptions to this are seabirds, lichens, marine benthic organisms, parasitic wasps, and soil nematodes)

- diversity tends to show an inverse relationship with altitude, especially in plants

- Diversity is greater in tropical regions than temperate ones, greater in coral reef habitats, coastal zones, and estuaries as well as marine ecosystems in comparison to temperate ones

- freshwater wetlands contain disproportionately high diversity at the landscape level

endemism

where a species is restricted to a particular area or region

how is rarity characterized? (essay question on this)

- small populations

- specialized habitat requirements

- restricted geographic range

example: Kirtland’s Warbler

note: densities of most species will become lower as diversity becomes higher in all scales

what lessens population densities?

- low reproductive and survival rates

- specialized diets (especially carnivores)

- the need for large areas to find food or complete their life cycles (especially with large territorial animals)

example: mountain lion

widespread distribution

when a species has a high probability that of persisting at regional or global levels even if particular areas with individual populations may be threatened or even exterminated

Restricted distribution

when a species is more susceptible to changes associated with:

- local or regional land use

- human population growth

- climate change

example: Haleakala Silversword