Conservation Bio Exam 3: Island Biogeography and Habitat Fragmentation

habitat degredation

changes in a habitat so that its ability to support population growth is reduced

island biogeography can also be applied to

habitat patches in vast degraded habitat ex. a patch of trees in middle to agriculture fields

oceanic islands contain … many of which are …

fewer species; endemic

deforestation

destructioin of forest ecosystems and their convsersion to other uses

desertification

conversion of grasslands and woodlands to vegetation types characterized by sparse cover and low productivity

habitat destruction often results in

habitat fragmentation

destroyed forests creates

isolated habitat fragments

reduced dispersal creates

metapopulations and subpopulations

habitat loss by ecosystem types

habitats are destroyed relative to how useful the biome is to humans

deforestation has led to

in-tact forest landscapes being very rare in tropical countries

desertification often results from

overgrazing which reduces ecosystem productivity by increasing soil erosion and compaction

habitat destruction leads to

isolated patches of intact habitat; habitat fragmentation

species area curves show

number of species on an island increases with island area

first hypothesis for greater species richness on larger islands

habitat diversity hypothesis: larger islands contain a greater diversity of habitats=opportunities for niche differentiation and coexistence

second hypothesis for greater species richness on larger islands

equilibrium theory of island biogeography: species richness of islands is related to island area and remoteness because these factors affect rates of immigration to the island and rates of extinction on the island

another way of phrasing equilibrium theory of island biogeography

remoteness of islands leads to distinctive factors

closer islands have higher

immigration rates; easier dispersal

large islands have higher

immigration rates; larger target

large islands have lower

extinction rates; more resources leads to larger populations

close islands have lower

extinction rates; rescue effect: new arrivals from mainland replenish numbers

testing hypotheses for species-area curves

species richness in carnivorous and herbivorous beetles vs island area

relaxation

reduction in species richness that occurs when the degree of isolation of a habitat patch increases

relaxation examples

glaciers receeding can create islands; creation of dams or canals can alter hydrology and fragment habitats

disharmony

representation of taxonomic groups in island biota are very different from representation of those taxonomic groups in continental biota or in areas of contiguous habitat

first example of disharmony

new zealand vs australia; before humans arrived new zealand had no reptiles or mammals; same sized areas in australia have many species of reptiles and mammals

second example of disharmony

mammal diversity in mexico vs the island of hispanola

first reason why we expect disharmony between island and continental biotas OR what are characteristics of organisms that are especially likely to be missing from habitat islands

species with poor colonization abilities are unlikely to arrive or to persist

second reason why we expect disharmony between island and continental biotas OR what are characteristics of organisms that are especially likely to be missing from habitat islands

species with naturally low densities or small population (top-level predators) are unlikely to persist on islands

third reason why we expect disharmony between island and continental biotas OR what are characteristics of organisms that are especially likely to be missing from habitat islands

species with specialist diets are less likely to be present on islands than species with generalist diets