WMAN 3v

Biogeography

Study of variation in species composition and diversity across geographic locations

Spacial scale: global

the entire world

spacial scale: regional

areas with uniform climate; species are tied to that region by dispersal limitations.

regional species pool (gamma diversity)

all species contained within a region

landscape scale

determined by topographic and environmental features.

Local scale

equivalent to a community

turnover

change in species

beta diversity

Change in species, or turnover, from one community type to another; connects local and regional scales.

biogeographic regions

Six divided land masses that correspond roughly to Earth’s major tectonic plates

continental drift

When the tectonic plates/ sections of Earth’s crust move or drift through the action of currents generated deep within the molten rock mantle.

vicariance

Evolutionary separation of species by barriers such as those formed by continental drift.

Speciation rate minus extinction rate

gives rate of species diversification

net diversification

net increase or decrease of species over time.

species–area relationship

species richness increases with area sampled.

• Species–area curves plot species richness (S) of a sample

against area (A).

• The relationship is estimated by linear regression:

S = zA+c

z = slope, c = y-intercept

matrix habitat

any kind of isolated area surrounded by dissimilar habitat

equilibrium theory of island biogeography

MacArthur and Wilson developed a theoretical model

– The number of species on an island depends on a balance between

immigration or dispersal rates and extinction rates.

– If immigration and extinction rates are plotted, the number of species

on the island should fall where the two curves intersect.

– This equilibrium number is the number of species that should

theoretically “fit” on the island, irrespective of the turnover or

replacement of one species with another.

BDFFP

goal was to study design of conservation reserves and maintenance of species diversity.

Landscapes

made up of a patchwork of communities of different types.

Regional species pool

Provides an upper limit on the number and types of species that can be present in a community.

Dispersal

Supplies species to communities. The importance of (this term) can be seen in cases of non-native species invasions.

Biotic resistance

occurs when interactions with the native species exclude the invader.

Resource partitioning

Competing species are more likely to coexist if they use resources in different ways.

resource ratio hypothesis

species coexist by using resources in different proportions.

Hutchinson’s model

-Time required for one species to exclude another (tc); depends on

population growth rates of the two species

– Time it takes environmental variation to act on population growth of the

two species (te)

– If tc << te, coexistence can’t occur, e.g. in environments with little

variability or if dominant species has very fast growth rates.

– In a fluctuating environment, tc >> te, competitive exclusion can occur.

– Coexistence can occur only when tc = te, a condition likely to be met

frequently in lake phytoplankton communities.

Intermediate disturbance hypothesis

first proposed by

Connell (1978):

– Species diversity will be greatest at intermediate levels of

disturbance.

– At low levels of disturbance, competition regulates diversity. At high

disturbance levels, many species cannot survive.

– There have been many tests of this hypothesis.

competitive displacement

he best competitor uses the limiting resources, reducing the weaker

competitor’s population growth to the point of extinction.

Dynamic equilibrium model

combines disturbance frequency

and rate of competitive displacement.

– Predicts maximum species diversity when disturbance level and rate

of competitive displacement are equal and at low or intermediate

levels.

Lottery models and neutral models

– All species have equal chances of obtaining resources made available

by disturbances, and this allows coexistence.

– Species must have similar interaction strengths and growth rates and

be able to respond quickly to disturbances that free up resources.

community functions

disease suppression,

plant productivity, water quality, etc.

provide valuable services to

humans, such as food and fuel production, water purification,

O2 and CO2 exchange, flood protection.

The Diversity–Stability Theory

A long-standing idea in ecology is that species richness is

positively related to community stability:

community stability

The tendency of a community to remain the same in structure and

function, or to return after a disturbance.

Complementarity hypothesis:

As species richness increases,

community function with increase linearly

Redundancy hypothesis

Functional contribution of additional species reaches a threshold.

Idiosyncratic hypothesis:

Strength of ecological function varies

greatly;

– Some species have a large effect, some have a minimal effect.

– Addition of dominant species will have a large effect on community

function, producing a curve with an idiosyncratic shape.

ecosystem

refer to

all the components of an ecological system, biotic and abiotic,

that influence the flow of energy and elements.

•t integrates ecology with other

disciplines such as geochemistry, hydrology, and atmospheric

science.

Primary production

The chemical energy generated by autotrophs during photosynthesis and chemosynthesis.

Gross primary production (GPP)

Total amount of carbon fixed

by autotrophs. Controlled by:

– Climate, through its influence on photosynthetic rate.

– Leaf area index (LAI):

Leaf area index (LAI)

Leaf area per unit of ground area.

Net primary production (NPP):

Amount of energy captured by

autotrophs that results in an increase in biomass (living plant

matter).

— = GPP – Respiration

• is the energy left over for plant growth and for

consumption by detritivores and herbivores.

Net ecosystem exchange (NEE).

The net change in CO2 is GPP minus total respiration:

Net secondary production

Ingestion – Respiration – Egestion

Chemosynthesis

Bacteria use chemicals such as H2S, HS–, and S2

– as electron

donors to take up CO2 and convert it to carbohydrates:

Trrophic levels

Feeding Categories

1st Trophic Level

Autotrophs or primary producers

2nd Trophic Level

Herbivores that consume autotrophs

Includes detritivores that consume dead organic matter

3rd (and higher) Trophic Levels

Carnivores that consume animals from the level below.

Omnivores

Organisms don’t fit conveniently into trophic levels, feed at multiple trophic levels

Detritus

Dead organic matter

allochthonous inputs

• Much of the detritus in streams, lakes, and estuaries is derived

from terrestrial organic matter.

• These external energy inputs are————-

autochthonous energy

Energy produced by autotrophs within the system is

The river continuum concept

– The importance of autochthonous energy inputs increases from the

headwaters toward the lower reaches of a river.

– Water velocity decreases, and nutrient concentrations increase, as

you go downstream.

2nd law of thermodynamics:

during any transfer of energy,

some is dispersed and becomes unusable.

– Thus, available energy will decrease with each trophic level.

Trophic pyramids

portray the relative amounts of energy or

biomass in each trophic level.

Terrestrial ecosystems

energy and biomass pyramids are

similar because biomass is closely associated with energy

production.

Aquatic ecosystems

biomass pyramids may be inverted.

Primary producers are phytoplankton with short life spans and

high turnover.

Trophic efficiency

Amount of energy at one trophic level

divided by amount of energy at the next lowest trophic level.

Consumption efficiency

proportion of available energy

ingested.

Assimilation efficiency

proportion of ingested food that is

assimilated; depends on food quality and consumer physiology

Production efficiency

proportion of assimilated food that

goes into new consumer biomass; related to thermal

physiology and size of consumer.

“Bottom-up” view

Resources that limit NPP determine energy

flow through an ecosystem.

“Top-down” view

Rates of consumption and other interactions

at the highest trophic level, influences multiple trophic levels

below them.

Trophic cascade:

Series of trophic interactions that result in

changes in biomass and species composition.

Food web

Diagram showing connections between organisms

and the food they consume.

– Shows qualitatively how energy flows from one component through

the ecosystem.

– As more organisms are added to a food web, complexity increases to

reflect complexity of real ecosystems.

– Feeding relationships can span multiple trophic levels (omnivory) and

may even include cannibalism (circular arrows)

Bioaccumulation

Some chemicals aren’t metabolized or

excreted, and become more concentrated in tissues over an

organism’s lifetime.

Biomagnification

Concentration increases in animals at higher

trophic levels, as they consume prey with higher

concentrations.

conservation biology

the scientific study of biodiversity, how human activities

impact it, and how to maintain it and prevent its loss.

ecosystem services

natural processes that

sustain life, such as water purification, soil formation, pollination of

crops, climate regulation, and flood control, which depend on the

integrity of natural communities and ecosystems.

Extinction vortex

A cyclic chain of events causes a small

population to decline even further and become ever more

vulnerable to processes that lead to extinction.

Habitat loss:

Conversion of an ecosystem to another use.

Habitat fragmentation:

Breaking up continuous habitat into

patches amid a human-dominated landscape.

Habitat degradation:

Changes that reduce quality of the

habitat for many, but not all, species.

Invasive species:

non-native, introduced species that sustain

growing populations and have large effects on communities.

Overexploitation

Harvest of wild organisms at a rate that

exceeds their replacement; contributes to the decline of many

species.

Population viability analysis (PVA)

probabilities of

population persistence are calculated under various scenarios.

used to:

– Assess risk of extinction of a population

– Identify particularly vulnerable age or stage classes

– Determine how many individuals are needed to establish a new

population

– Determine a safe number of animals to harvest

Ex situ Conservations

In some cases, the only hope for

extremely small populations may be to remove the species

from its habitat and propagate it in sheltered conditions.

Surrogate species:

Protecting habitat for one species, such as the

red-cockaded woodpecker, can result in protection of other species

Flagship species:

A charismatic surrogate species that people will

want to give protection to, such as the mountain gorilla.

Umbrella species

Protection of its habitat will serve as an

“umbrella” to protect many other species with similar habitat

requirements.

– They usually have large ranges (grizzly bear) or specialized habitats (red-

cockaded woodpecker), or are easy to count (butterflies).

Gap Analysis Program (USGS)

used to identify species of

concern that are not adequately represented on existing

conservation lands.

Landscape ecology

examines how landscape patterns are

influenced by ecological processes and how these spatial

patterns influence ecological processes.

Landscape

Area in which at least one element is spatially

heterogeneous; often includes multiple ecosystems.

mosaic

a composite of heterogeneous elements.

Landscape composition:

Kinds of elements or patches and how

much of each kind is present.

Landscape structure:

Physical configuration of the landscape

elements.

Characterized by:

– Size of patches

– Whether patches are aggregated or dispersed

– Complexity of patch shape

– Degree of fragmentation

Scale

very important in landscape ecology; can vary

depending on the size of the area viewed.

Grain

size of the smallest homogeneous unit of study (e.g., a pixel

in a digital image); determines resolution.

Extent

boundary of the area or time period encompassed by the

study.

Biogeochemical “hot spots”

regions where chemical

reaction rates are high.

Edge effects

biotic and abiotic changes associated with this

boundary.

• The physical environment changes over a certain distance into

the fragment, and thus biological interactions and ecological

processes change as well.

Edges

(total length of habitat boundary) increase as

fragmentation increases.

core natural areas

where

conservation of biodiversity and ecological integrity take

precedence over other uses.

Populations in ——— can maintain themselves, and be

sources of individuals for other populations.

• Ideally, ——— provide enough land to meet the large

habitat area requirements of top predators.

Biological reserves

smaller reserves with conservation of a

single species or ecological community as the main objective.

• Although small, they can be important, especially where

human population density is high and large reserves are not

feasible.

buffer zones

areas with less

stringent controls on land use but still provide habitat for many

species.

Habitat corridors

Linear patches that connect blocks of

habitat.

Ecosystem management

a way to include protection for all

native species and ecosystems and focus on the sustainability of

the whole ecosystem.

adaptive management

an iterative process where policies can be adjusted as needed

• Biogeochemical Cycling

– Pool, or reservoir: amount of an element in a component of the

biosphere.

– Flux: rate of movement of an element between pools.

– Example: terrestrial plants are a pool of carbon; photosynthesis

represents a flux.

• Global carbon cycle

– C moves between atmospheric, terrestrial, and oceanic pools over

weeks to decades.

– Changes in the global C cycle are influencing Earth’s climate.

– C in the atmosphere occurs primarily as carbon dioxide (CO2) and

methane (CH4). Both are greenhouse gases.

– Major pools of C: Atmosphere, oceans, land surface (soils and

vegetation), sediments and rock.

– 99% of global C is in sediments and rock, the most stable pool; fluxes

occur on geological time scales.

• Oceanic pool:

– Ocean surface water takes up CO2 from the atmosphere by diffusion.

– C is transferred to deeper water mostly as organic detritus and

carbonate shells.

– Upwellings bring C-rich water to the surface, releasing CO2 to the

atmosphere.

• Terrestrial pool:

– Soils contain twice as much C as plants.

– CO2 is exchanged with the atmosphere mostly by photosynthesis and

respiration.

– Prior to the Industrial Revolution, these two fluxes were roughly

equal, with no net change in atmospheric CO2.