Biodiversity Last time Species Concept Biodiversity Measuring - PowerPoint PPT Presentation

Biodiversity Last time Species Concept Biodiversity Measuring Biodiversity

Biodiversity Today Last time Endemism Species Concept Rates of species formation Biodiversity Mass Extinctions Measuring Biodiversity Species Area Relationship

Endemism Endemics – Species found in a particular region but no where else. Endemism – proportion of species in an area that are endemic.

Endemism

Rates of Species formation 3 major rapid origins of species diversification • Cambrian (500mya) • Paleozoic (440mya) • Triassic (250mya)

High rates of speciation • Mass extinctions – after permian extinction it took 50 million years to regain same # of families. • Increasing separation of land masses across earth. • Evolution of new life forms and types of species interaction.

Number of Species

Rates of Extinction • Background extinction rate • Mass extinction

Rates of Extinction • Background extinction rate • Mass extinction 1. Cambrian 50% of animal species 2. Devonian 75% of species 3. Permian 95% of marine and terrestrial organisms (trilobites) 4. Triassic 80% of reptiles and 65% of all species 5. Cretaceous Dinosaurs and other large reptiles

Rates of Extinction • Background extinction rate • Mass extinction 1. Cambrian 50% of animal species 2. Devonian 75% of species 3. Permian 95% of marine and terrestrial organisms (trilobites) 4. Triassic 80% of reptiles and 65% of all species 5. Cretaceous Dinosaurs and other large reptiles Species richness not directly affected by mass extinction

Rates of Extinction Current • extinction rate 100 to 1000 times of past geologic periods • Extinction for birds and mammals 1species per decade (1600 - 1700); One species per year (1850 - 1950). •Does not take into account T&E species •99% of modern extinction can be attributed to human activities. •Islands have higher extinction rates; � of extinctions occur on Islands (1600 - present).

Carolina Parakeet extinct around 1935? (1918?)

Panthera leo barbaricus Barbary Lion Extinct 1922

Tasmanian Tiger Extinct 1936

Gastric brooding frog • Extinct ? • Not found since 1985

Aldabra tortoise Seychelle saddleback Seychelle tortoise http://members.aol.com/jstgerlach/tortoise.htm

Species-Area relationship c is a taxon specific constant z is the extinction coefficient is in the range 0.1 to 0.3 Number of species S Area A

Species-Area relationship c is a taxon specific constant z is estimated using the slope log(Number of species S) log(Area A)

Mac Arthur and Wilson (1967): the theory of island biogeography