Ecology Exam 2

Alternative Stable States

—caused by addition or removal of organisms, e.g. human activities are shifting communities (intro of caulerpa to Mediterranean)

What drives community composition?

-climate, tide, biotic and abiotic factors, geographic factors

Currents

-drive what’s going on with physical movements -deeper water is cooler so things settle -warm east, cold west

Biogeography

-study of patterns of species composition and diversity across geographic locations, e.g. highest diversity in the amazon is in the treetops -latitude flatitude

Patterns of biodiversity

-varies in latitude, closer to equator (lower latitude) is more diverse -varies based on continent

Global Scale

-species are isolated - speciation, extinction +dispersal determine differences

Regional Scale

topographic + environmental features of the region

Landscape Scale

-areas with uniform climate -ties by dispersal limitations -gamma diversity: all different species contained within a region -can be considered biome

Local Scale

-alpha diversity: species diversity (linear line) -very tied to regional scale -Beta diversity: change in species

General species diversity patterns

-area increase -rainfall increase -productivity increase -latitude decrease -habitat complexity increase

Regional species

-provide raw material for local assemblages -local richness=regional richness -proportional to each other, regional processes dominate -local richness levels off, local process dominates

Witmen et Al.

-regional species explained only 75% of local species richness (orange line) -regional process important

Global Species Diversity Patterns and Comp

influenced by: -geographic area and isolation -evolutionary history -global climate

Global BioGeo

-Alfred Russel Wallace -natural selection -studied species distribution across large spacial scales

Malay Archipelago

-Philippines mammals similar to those in Africa - evolved on 2 dif continents

Main idea

-land masses divided into 6 major bioregions w/ their own biota and species richness -plates move via continental drift -convergence: mountains and subduction zones -divergence: mid ocean ridges, rift valleys

subduction zones

increased volcanic and seismic activity, trenches created

Evolution by Vicariance

separation by physical geographic barrier

Gradient of species diversity with latitude

-diversity decreases as you move away from equator -seabirds and marine biota don’t follow this pattern

Mountains Case Study

• rich in biodiversity prior to eruption

• post eruption was devoid of life

• foundational principle: communities are dynamic

What can cause changes in community?

• migration

• disease

• weather events

• humans

Coral Reefs + Indian Ocean

• gradual turnover of dominant species

• catastrophic events like coral bleaching and 2004 tsunami

• corals have symbiotic relationship with zelplankton

• positive feedback loop with coral bleaching events

Sucession

a change in species composition in communities over time; colonization or extinction due to change

What can cause succession changes

• can result from biotic or abiotic factors

• abiotic: weather events, vary over time scales

• biotic: predation, disease, competition

Coral Bleaching

• caused by high water temp

Disturbance

abiotic event physically killing/injuring some individuals

and creating opportunity for others

Stress

factors reducing growth, reproduction, or survival

Biotic factors

• ecosystem engineers + keystone species (beavers, algae, crawfish)

• Iceland experiencing mosquitos for first time

• CWD: fatal neurological disease in deer, moose, elk, and reindeer

• invasives like honey suckle; resilient to environmental changes

sucession types

• Primary: increased intensity, decreased frequency, brand new system

• Secondary: increased frequency, decreased intensity, adjusted system

• little: decreased frequency and intensity

• climax stage: stable end point with minimal change

Space for time substitution

• henry lowels

• using space for time, look at one spot and move across gradient to see succession

• sand dunes of lake michigan: as sand is deposited on shore precious organisms/plants are pushed back (older plants at back), primary succession at shore, later succession further back

Pioneer stage

dominated by pioneer species who are hardy, fast-growing organisms and occurs from primary succession

Stages of Succession

• early stages: facilitation, plants modify habitat in different ways

• later stages: inhibition, elders have - affect on later species

• spruce stage: tolerance, 1 species dominates w/ slow-growth

Views on Succession:

• Clemens: climax communities can be maintained indefinitely; climax community is dominant stable organisms that won’t change easily

• Gleason: believed communities not predictable, each unique

• Eaton: believed organisms + environment interact to shape succession, environment has unpredictable impacts

• overall, communities can reach a climax, but all look dif. based on environment and organisms

Facilitation model

early species modify the environment in ways that benefit later species, lead to climax community

• prevents 1 species from dominating

Tolerance model

assumes early colonizers modify community in neutral ways

• early species have little to no effect on later species

Inhibition model

early species modify community in ways that inhibit

later species succession

• early species prevent later species from being able to establish themselves

• early species dominance remains until some sort of stress or disturbance comes along

Succession Progress

large, slow growing, long-lived dominance

alternative stable states

dif. communities develop in the same area under similar environmental conditions (like marvel multiverse)

Stable

return to orignal state after disruption

Global Biogeo

-increased latitude, decreased richness.

-global seabirds and marine productivity don’t follow this.

Gaston et Al.

-measured multiple families along north-south transects

-Hot Spot: high species richness under threat from human activity.

-U.S. hotspots in west coast, hawaii, app mtns

-Salamander hotspot in U.S. East coast

Tropics

-Greatest biodiversity; climatically stable, large food sources, rainfall, vast habitat

-largest land area + stable temps: midline of earth bulges rather than being perfect (more habitat available, lower extinction rates)

-climatic stability (time to evolve): tropics is origins of species and then they spread towards the poles, number of taxa decrease s you move from the equator, jablonski et al

-High productivity (larger carrying capactiy): tree ring growth, diversity lower during cooler temps

Tropics Ideas

1. glaciation drives species to the tropics

2. tropics too hot during greenhouse conditions

Species Area relationships

-species richness increases w/ area sampled

-steeper slope = greater difference in sampling area

What is an island

any isolate area surrounded by a sea of dissimilar area

• a large island has more species than a smaller island

McArthur and Wilson

bird species richness in New Guinea Islands

-equilibrium theory of island biogeography

Island Diversity

1. positively correlated to island area

2. strong negative relationship to source distance

Number of species is balanced by

-immigration + dispersal rates

-extinction rate

Immigration + Extinction

intersection equals equilibrium

-assume island size controls extinction rates

Small islands

-higher extinction rates

-only certain things will be able to immigrate to other islands; less things make it to distant islands

Krakatau

-mcarthur + Wilson calculated immigration and extinction rates of birds

-predicted 30 species at eq

Florida Mangroves

-simberloff and wilson: removed all insects, 1 year past removals islands closer to mainland bounced back faster

-further islands didn’t recover to og numbers

-mainland areas have higher immigration rates

-extinction lower = continual immigration

-mainlands have high likelihood of being rescues, lower chances of extirpation

Forest Fragments

-lovejoy began longterm experiment: control is forrested, experimental is logged land.

-largest fragments lost 50% understory birds (1,00 hectares no enough to maintain diversity)

-10k hectares needed w/o forest regeneration

-1,000 needed to maintain species

-short distances hinder colonization

Fragmentation

-leads to edge effects: how forest edge impacts species diversity

-likely to result in loss of more species

Local Scale

Influenced by regional

Hantavirus

-transmitted by rodents

Suzan et al

-experimental removal of small mammals
-studied impact of host abundance on infection rates

-SNV and deer mice

-decreased small mammal diversity led to increased affected individuals

Species diversity in Communities

-essential for regulating communities

-important for human protection

-identify potential “emergent hotspot”

-decline in small mammal diversity is a sign of a potential hotspot

Factors controlling community Membership

1. regional species pool and dispersal ability

2. environmental conditions

3. species interactions

Biotic Resistance

-factor preventing domination

-decreased diversity more prone to being invaded

Climate + Invasions

1. alter disposal pathways: European green crabs

2. alter environmental constraints and distributions: warm winters allow persistence

3. alter conditions of interactions: current is divided by temp gradient, if it’s warmer green crab dominates over red

Coexistance

-macarthur studied warblers

-feeding and breeding habits, nesting locations, breeding territories

-found different warblers use different parts of habitats in different ways

-resource partitioning

Resource partitioning

-species more likely to coexist if they use different resources

-partition based on size

How is competition related to resource use?

avoiding resource overlap leads to decreased competition

Narrow v Broad resource overlap

Narrow: less competition, higher species richness

Broad: more competition, similar richness