Biodiversity and Geography of Extinctions

Question 1

Mass extinction

Answer 1

when the earth loses 75% or more of its species in a short interval

Question 2

The big five

Answer 2

Ordovician event 86% loss- caused by glacial episodes, marine transgressions and regressions, and uplift and weathering of appalachians affecting atmospheric and ocean chemistry

Devonian event 75% loss- global cooling followed by global warming possibly tied to diversification of land plants, evidence for widespread deepwater anoxia and spread of anoxic water by transgressions , drawdown of co2

Permian event 96%- siberian volcanism. Global warming, spread of deep marine anoxic waters, elevated H2S and CO2 concentrations in land and water, ocean acidification

Triassic event 80%- Central atlantic magmatic province thought to have elevated C02levels-> increase in global temp, and calcification crisis in world oceans

Cretaceous event 76%- Meteor impact in the Yucatan-> caused rapid cooling. Preceding impact biota might have been declining due to volcanism resulting in global warming, tectonic uplift altering biogeography and accelerating erosion, causing ocean eutriphocation. CO2 spike just before extinction. Drop during extinction

Question 3

Constitues a mass extinction

Answer 3

Rate and Magnitude
Rate- number of extinctions / time it occured
Magnitude- percent species gone extinct

When 75% or more disappear in >2my

Question 4

6th mass extinction?

Birds

Answer 4

Extinctions for birds are best documented:
150 bird species have gone extinct in the past 500 years and 3 species have gone extinct since 2000.

Estimated extinction rate over the past 2.5 my was 1extinction/83 years.

Question 5

6th mass extinction?

Amphibians

Answer 5

Species are showing dramatic declines even where suitable habitat remains - reasons unknown.
If threatened species go extinct in the next 100 years then extinction rates will be 10x recent rates.

Question 6

Linnaean shortfall

Answer 6

the disparity between the number of known species and the number of species that actually exist
-new species are being found everyday
ex. 3 new flowering plants were found in mexico in the past 20 years
349 new species of mammals were discovered in a 10 year period

Question 7

Challenges in measuring extinction

Answer 7

1) We could be losing species we don’t even know exist

2) Measures of species extinctions may underestimate the problem

Question 8

Patterns of extinction

Answer 8

island life more susceptible to extinction.
Recently extinction rates of continental animals have risen relative to ocean islands caused by insularity (caused by habitat conversion and fragmentation)

Question 9

Extinctions are preceded by declines in geographic changes

Answer 9

Ex. Giant panda, red wolf and black-footed ferret
Each maintains a small remnant population at the periphery of the historical range

Komodo dragon persists on true islands and isolated regions of the former range (on Flores island)

Question 10

Contagion and Peripheral diversity hypotheses

Answer 10

Contagion: populations persist in isolated areas as extinction proceeds along predictable routes

Peripheral diversity: higher diversity of peripheral areas and adaptation to diverse marginal environments may allow persistence of peripheral populations.

Question 11

Biodiversity hotspots

Answer 11

areas where geographic ranges of many species overlap

Hotspots of endemism are very important
Extinction probability increases with decreased range size

Many bird hotspots are in the tropics
Reefs are important
Areas of endemism for birds and invertebrates don’t overlap

Threatened land animals are in south/southeast asia, threatened marine are in N. atlantic, pacific and SE asia

Question 12

Problems

Answer 12

Tropics: terrestrial habitat loss, high harvesting in asia

Marine mammals: by-catch, vessel strikes, ocean pollution

Question 13

Evolutionary significant Unit

Answer 13

to develop an empirical definition of intraspecific groups that are the most important units for conservation below the species level.
ESUs represent the heritage of a species as well as groups with distinct characteristics and tendencies

Found using mtDNA

Question 14

Identification of ESUs

Answer 14

Biogepgraphical principles used to identify ESUs
ex. measuring distinctiveness of rainbow trout populations across BC
To be ES population should be located in an unusual habitat or display unique phenotype

Ex. strong genetic differentiation between adjacent populations of grey wolves between coastal and inland populations

Question 15

Evolutionarily Distinct and Globally Endangered Species (EDGE)

Answer 15

Save as much as possible. How to rate which are most endangered or should be saved?

1) amount of unique evolutionary history represented ED
2) Conservation status (global endangerment)