Extinction of Species Midterm

Three levels of diversity

Genetic diversity

Species diversity: the range (number) of species in a given area

Ecosystem: how species interact within each other and their physical environment

Genetic diversity is high if:

number of different alleles is high

heterozygosity is high

Long term effect of genetic diversity loss

Loss of ability to adapt to future change

Short term effect of genetic diversity loss

Inbreeding depression and compromised disease resistance

Morphological species limitation: who uses and limitations?

taxonomists to categorize unknown species

but individuals of the same species can all look very different from one another - and different species can all look the same

Biological Species Definition

Species are all animals that can mate together

Conservationists use

Limitations: hybridization, the possibility of interbreeding if geographical barriers are removed.

Evolutionary species concept limitations

May be counterintuitive: morphological different species can be closely related

What are the three levels of biodiversity (4 pts)? Provide one reason why it’s
important to conserve each of three levels (6 pts)?

Genetic: able to survive environmental changes, diseases, or other disturbances. 

Species: greater variety of species leads to a more resilient and stable ecosystem

Ecosystem: more interspecies interactions make ecosystems more resilient to disturbances.

ecologically extinct

persists in such low numbers that its effects on other species is insignificant

Current extinction rate is ___________ above background rate

100X to 1000X

Mass extinction definition

Elevated extinction rates that lead to asharp decrease (>75%)

in the number of species in a “short” time span (~2 million years)

How does the current “mass extinction” compare to past mass extinctions?

Extinction RATES are much greater.

Extinction MAGNITUDES are much smaller.

If nothing changes, extinction magnitudes will eventually catch up (200-2000 years).

biases in documentation

Species extinction is best documented in more wealthy countries - the most amount of extinctions appear to occur there.

Of the sinister 6: what are currently the biggest drivers?

Over-exploitation, habitat loss, and introductions of invasive species

Of the sinister 6: what are emerging threats?

Climate change, pollution and disease

How is the geographical distribution of extinctions changing?

From species-poor islands to species-rich mainlands.

Endangered species are concentrated in __________

the developing world

UTILITARIAN VALUES

Goods, services, information, inspiration

Monetizing and quantifying utilitarian values (5)

Commodity values: pay when there is a market for the species

Option values: pay to guarantee the option of finding future use for a species

Contingent values: pay for the opportunity to use a species

Existence values: pay to keep a species from going extinct, even if they never actually use it (or even see it)

Bequest values: pay to ensure future generations have opportunity to use a species

Rosy periwinkle argument

Species may have a use that hasn’t been discovered yet

SAFE MINIMUM STANDARD

Assumes that biological diversity is of incalculable value and should always be conserved unless the costs of doing so are intolerably high.

Shifts burden of proof to those who seek to threaten species.

Anthropocentic ethic

species are resources that exist to benefit human beings; needs of people are always paramount

Stewardship ethic

human beings are responsible caretakers of wild species

Biocentric ethic

individual human beings should respect rights of individuals of other species

Ecocentric ethic

the human species is coequal with other species which should should not be threatened by human actions

Taxonomic group with highest number of species

Insects

Patterns of diversity: Biogeography: Size of Area

Larger size = more species diversity

Species-Area Relationship - 10x increase in area results in ~2x increase in species

Patterns of diversity: Environmental Gradients: Productivity

Precipitation and year-round warm temperatures increase primary production

Patterns of diversity: Environmental Gradients: Latitude and Elevation

General pattern of increasing diversity with decreasing latitude and elevation

Patterns of diversity: Environmental Gradients: Complexity

More complex ecosystems have greater species diversity.

How do Disturbance Regimes affect species diversity?

Too much or too little can reduce diversity.

Species Richness

The number of species in an area

Alpha Richness

the number of species within a local area

Can also be calculated as the average richness in local areas within a larger region.

Gamma richness

the total number of species across a larger region

Beta richness

the change or turnover of species across a region.

Beta = Gamma / average alpha richness

3 determinations of species “hot spots”

– Species diversity

– Levels of threat

– Endemism (species found only in one area)

Benefits of “hot spot” approach

Allows resources to be focused in specific areas - much cheaper.

Criticisms of hot spot approach

Protecting hotspots doesn’t necessarily conserve the full range of speciesdiversity

Do not consider genetic diversity (evolutionary potential)

Do not consider ecosystem processes and services, only species diversity

Often do not consider differences of cost of land among hotspots

Ecosystem/Habitat Approaches

Focus on habitats and ecosystems that protect vital ecosystem processes and services

Microevolution vs macroevolution

Micro - changes over one generation

Macro - changes over multiple generations

Allopatric speciation

a single population is split into two populations by geographic barrier that then evolve into separate species

Pre-zygotic reproductive isolation

Habitat, temporal, or behavioral mechanisms that prevent the formation of viable zygotes.

Post-zygotic reproductive isolation

Mechanisms that prevent “hybrid” individuals from passing on their genes

What can cause adaptive radiation

Novel adaptations: open new niches

Extinction: open existing niches up to new species.

Why won’t speciation save us?

Many species threatened are the only remaining species of their genus or family.

No closely related species that can evolve and replace if threatened species goes extinct

What slows speciation rate?

Loss of genetic variation in small populations

Loss of populations occurring in different habitats

Net: high extinction and low speciation means loss in diversity.

ESA Mission

"The purposes of this Act are to provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved”

What administers the ESA?

U.S. Fish and Wildlife Service - terrestrial and freshwater species and some marine mammals

NOAA Fisheris - marine animals

What’s not covered under the ESA?

Plant and invertebrate populations do not typically get special consideration

How are species listed in ESA?

Anyone can petition to have a species listed

Economics (should) not be considered)

Sympatric speciation

Speciation occurring without geographic barriers. Niche preference. behavioral barriers, temporal barriers

Prohibited acts under ESA:

Possess, sell, deliver, carry, transport, or ship any such species

Import any species into, or export any species from, the U.S.

“Take” any such species within the U.S. or on the high seas

PLANTS AND INVERTEBRATES ON PRIVATE LAND AREN’T PROTECTED

“Take”

to intentionally harm, harass, pursue, hunt, shoot, wound, kill, trap, capture, or collect or attempt to engage in any such conduct

Includes significant habitat degradation

“Incidental take”

Take that results from some activity that is not unlawful.

ESA EFFECTIVENESS

Species typically aren’t delisted BUT awareness has improved and extinction risk has lowered for listed species

Habitat Conservation Plan:

legally binding plan that outlines how a landowner:

– Can proceed with incidental take

– Will minimize harm to listed species during development

– Will mitigate unavoidable harm by protecting or restoring habitat

most important factor threatening most taxa

habitat destruction

Primary driver of habitat loss

Agriculture

Species-Area Relationship -

10x increase in area results in ~2x increase in species and vice versa

Fragmentation increases extinction by reducing:

population sizes, immigration, emigration and “colonization” of habitat patches

Theory of Island Biogeography: Extinction of species is influenced by -

Island Area (small > large)

Theory of Island Biogeography: Immigration of species is influenced by -

Isolation of island from other islands (near > far)

Edge effects:

altered environmental and biological conditions at the edge of fragmentation

Results in interactions between “interior” and “edge” species

Alters microclimates 100s of meters into patch interior

Smaller patches have more edge than larger patches

Three Approaches for Maintaining Habitat

Protection: prevent further habitat loss

Management: actively managing habitats to maintain species of conservation concern

Restoration: actively restoring lost or degraded habitat to a state where is benefits species of concern

_____ and _____ habitat patches have higher diversirty

Large and close to mainland

What made diseases go from an issue with only population-level effects at worst to a major threat to biodiversity?

Globalization (more disease introduction)

human activity (more disease introduction and stress on animals)

Environmental Change (stress and expanding disease ranges)

Disease-induced extinctions usually occur due to:

A naïve host population

Pathogen does not depend on host density

The presence of multiple hosts (reservoir hosts)

What caused susceptability to Devil Facial Tumor Disease?

behavior facilitates transmission

extremely low genetic diversity prevents new hosts from rejecting the tumor

What causes exotic species introduction?

Deliberate introductions

Inadvertent introductions (stow-aways)

INDIRECT HUMAN AGENCY

INDIRECT HUMAN AGENCY

“Natural” colonization made possible by human activities:

• Creating new habitat for species to colonize

• Climate changed-induced range expansions

primary driver of bird and mammal extinctions (86%) on islands

Invasive species

4 characteristics of successful invasives

– wide habitat tolerance

– good dispersal capacity,

– high intrinsic rate of growth,

– tolerant of humans (commensalism)

What makes some habitats more vulnerable to invasion?

low species diversity

recent disturbances

In the case of islands, also “naïve” prey, hosts, and competitors

4 ways that invasive exotic species can displace native species

predation, competition, disease/parasitism (exotic pathogens), and habitat alteration (ecosystem engineers)

Controlling Early stages or small-scale invasions

Physical/lethal control such as trapping/shooting animals, digging up plants

Controlling Widespread invasions

Chemical control (pesticides, herbicides)

– Contraception/Sterilization

– Biological control

Ways to reduce cats impact outside

Visual alerts

Obstructions - devices that get in the way of hunting.

Auto alerts

- cats are creative and tend to find a way around these

How did barred owls invade?

“Native invaders” - human activity expanded habitat

What gives barred owls a competitive advantage over spotted owls?

Barred owls are larger and more competitively dominant

Ecosystem Effects of Barred Owls

Eat many at-risk amphibian species

Best control for barred owls?

Lethal removal - but requires a lot of work in areas with high barred owl density

Also very controversial because barred owls are native invaders

Why do we overexploit?

Lack of knowledge, carelessness

We value rarity

We are prejudiced against particular species

Socioeconomic causes of overexplaitation vulnerability

High commercial value

International commerce

Human prejudice

Life history characteristics that increase vulnerability to overexploitation

Naturally rare

Low growth rates

Large body size

Patchy distributions

International range/movements

5 Types of Overexploitation

Commercial exploitation

Subsistence exploitation

Recreational exploitation

Persecution of “pests”

Inadvertent killing

3 ways to Regulate Commercial Exploitation

Illegal markets reduce effectiveness

Use market forces

Change the customs

Combat subsistence overexploitation

Alternative income and food sources

Challenges to sustainable harvest

Variable estimates of population size and growth

Maximum Sustainable Yield (MSY) varies with environmental conditions

Harvest can be ecologically unsustainable even if numerically sustainable

What made sharks vulnerable to extinction?

slow growth and low reproductive rates,

How does marine overexploitation cause Indirect Effects on Terrestrial Species

Fishery depletion increases local society’s dependence on other food sources (such as illegal game hunting and poaching)

Why are Marine Species Overexploited? (4 reasons)

Commerce and Demand

Technological Advances

Weak Regulation and Enforcement

Destructive Fishing Practices

How Coastal Habitat Degradation further affects overharvest vulnerability

Degradation of spawning habitats (e.g., rivers, estuaries, coral reefs, mangroves) compromise species ability to withstand harvesting

5 Solutions to marine overharvesting

Management and Regulations

Marine Protected Areas

Aquaculture (not really - causes more problems)

Less Destructive Fishing Practices (especially reducing bycatch)

Consumer Decisions

Passenger pigeon nesting

Nested in huge colonies wherever they found an abundant mast crop

Only one egg in clutch

1871 PASSENGER PIGEON NESTING Event

Hundreds of millions of pigeons — Largest nesting ever recorded

Many tens of millions were killed

Legislation as a result of pigeon extinction

THE LACEY ACT (1900)

PELICAN ISLAND NWR (1903)

MIGRATORY BIRD TREATY ACT (1918)

Social and technological causes for passenger pigeon extinction

MARKET HUNTING made overharvest insanely profitable

TELEGRAPH SYSTEM AND RAILROADS allowed communication and rapid movement to nesting sites.

Climate change temperature changes: highest and lowest

highest change in polar regions

lowest change over ocean

How Does Climate Change Impact Species? (4 ways)

Direct, physiological effects

Habitat changes (ex. coat color mismatch, habitat shifts)

Ecological mismatches (changes in the timing of ecological processes like insect population growth and migration)

Novel diseases, predators, and competitors

Habitat shifts

To northern habitats and up to higher altitudes