ecology final

landscape ecology

the field of study that considers the spatial arrangement of habitats at different scales and examines how they influence individuals, populations, communities, and ecosystems

corridors

linear patches

current habitat heterogeneity is a reflection of

recent and historical events caused by natural and human forces

example of legacy effect

In Eastern deciduous forest, previous land uses (pasture, plowed, or cut only) affect soil conditions and today's forest species composition.

In Everglades, heterogeneous habitats reflect geological, biological, and social-economic drivers.

what causes habitat heterogeneity

Natural forces (e.g., tornadoes, hurricanes, floods, mudslides, fires)continue to cause habitat heterogeneity.

Human activity has influenced the intensity, frequency, and ecological influence of natural forces

example of factors that cause habitat heterogeneity

Throughout the twentieth century ,natural fires were suppressed in Yellowstone National Park.

In 1988, hundreds of fires were ignited by human activity and natural forces (e.g., lightning).

Patterns of burning depended on landscape characteristics (e.g., amount of plant litter, wind patterns).

example of how human activity causes habitat heterogeneity

Humans act as ecosystem engineers by constructing buildings, dams, irrigation channels, etc.

Example:Villages and farms built by the Romans were abandoned by the fourth century CE.

Ancient building materials broke down and contributed minerals to the soil; introduced crop species remained in the landscape.

Recently, researchers found that sites closer to settlements had high soil pH, more phosphorus, and greater species richness.

habitat diversity increases along what type of gradient

local to landscape scale

example of local vs. gamma diversity

In a survey of birds along 27 streams in Vermont, researchers found that each stream supported ~17 species (i.e., alpha diversity), whereas the combination of streams supported 101 species (i.e., gamma diversity).

This occurred because habitat features (e.g., resource types) were heterogeneous among streams and different birds preferred different habitat characteristics.

example of species sorting

A researcher sowed seeds of 20 wetland plant species in artificial wetlands that varied in features such as soil fertility and flooding rate; only certain species from the regional pool survived under each wetland combination

the number of species \_______ with increased habitat area

increased

the species area relationship can be observed in a \_______ range of ecosystems with \____________ different types of organisms

wide; many

example of species-area relationship

Robert MacArthur and E. O. Wilson found that amphibian and reptile species richness on the Caribbean islands increased with island area.

The relationship between species richness and area relationship is curvilinear when area and species are plotted on a regular scale, and linear when plotted on log scales.

Across many different groups of organisms, the slope (z) ranges from 0.20 to 0.35 across scales of 1 m2 to the area of an entire country.

example of habitat fragmentation

In 1940, forests in Costa Rica covered much of the country.

As human populations increased, forests were cleared.

Today, forests that remain exist in many small fragments (habitat islands).

effects of fragment size

Fragmentation decreases habitat area and increases patch number, edge size, and isolation. Small habitats have small populations which are more likely to go extinct

-increases the amount of edge habitat compared to the original unfragmented habitate

example of fragment size impacts

Damming of a large river in Venezuela created islands of varying sizes.

Predators on small islands quickly went extinct because there were not enough herbivore prey to sustain populations.

Increased herbivore abundance on small islands led to an increase in tree mortality and a decrease in tree recruitment.

example of fragment effect on edge habitat

An unfragmented piece of land with an area of 1 ha has a total edge length of 400 m.

The same area divided into 16 smaller square habitats has a total edge length of 1,600 m.

An increase in edge habitat changes the abiotic conditions (e.g., ground temperatures in a forest) and the species composition of a habitat.

example of species that prefer edge habitat increasing in abundance after fragmentation occurs

The bronzed cowbird is a nest parasite that reproduces by placing its eggs into nests of other birds, which allows it to reproduce without the cost of parental care.

Cowbirds spend most of their time in fields, but enter the forest to find nests to parasitize.

In the southern United States, an increase in edge habitat has led to an increase in cowbird abundance.

Increased cowbird parasitism has decreased abundance of species whose nests are parasitized.

stepping stones

small intervening habitat patches that dispersing organisms can use to move between large favorable habitats

useful for flying organisms that do not need continuous corridors to disperse

the quality of \_________ helps to determine whether organisms can move between fragments

matrix habitat (habitat between fragments)

example of effect of matrix habitat on species movement

Many butterflies feed in meadows and disperse between meadows through matrix habitats.

Researchers in Colorado questioned whether butterflies preferred to disperse through matrix habitats containing willow thickets or through coniferous forests.

They mapped locations of meadows, willow thickets, and coniferous forests in a valley, and studied the movement of many butterflies from six taxonomic groups.

Four of the six groups were 3 to 12 times more likely to disperse through willow thicket habitats than through coniferous forests.

the equilibrium theory of island biogeography incorporates both

habitat area and isolation

theory of island biogeography

-MacArthur & Wilson

-species richness increases with island area

-islands closer to the mainland receive more colonizing species

-to test hypothesis: measured bird species richness on 25 islands in the South Pacific

-found that larger islands contained more species

-among islands of similar size, near islands contained more bird species than far islands

example of the effects of patch size and isolation being similar across multiple types of habitat

In the southwestern United States, 26 species of mammals prefer to live in mountaintop habitats.

Researchers questioned how mountaintop size and isolation from source habitat (i.e., Rocky Mountains and the Mogollan Rim) affect mammal species richness.

They discovered more species on larger and less isolated mountaintops.

experimental test of island biogeography theory

Daniel Simberloff and E. O. Wilson conducted a manipulative experiment to test effects of habitat size and isolation.

On a set of "islands" in the Florida Keys, they observed that "islands" closer to the mainland had more insect species than islands farther from the mainland.

They built tents over selected islands, and fumigated them to kill all insects.

They removed the tents and allowed species to naturally recolonize.

They found that more insects recolonized islands closer to the mainland, and species richness of islands was similar to values before fumigation.

species turnover

Changes in species composition on islands resulting from some species becoming extinct and others immigrating

-dynamic

Nature Preserve Design

Understanding the effects of island size and shape on populations has helped to design nature reserves.

Since large areas can support large populations with low extinction rates, setting aside a single, large area will better protect biodiversity than will several small areas.

Reserves also need to be close enough to allow dispersal, but far enough to reduce dispersal of diseases and parasites.

The benefits and disadvantages of edge habitat must be considered; round areas have less edge-to-area ratios than rectangular areas.

Nature reserves are typically a compromise among various options.

total species richness is highest near the \_________ and declines towards the \________-

tropics; poles

in the northern hemisphere, species richness of most animal and plant groups increase from

north to south

mammal species richness increased to the \_______

west

-likely due to the habitat heterogeneity of mountains

processes underlying patterns

at any given latitude, there are more species where there is greater ecological heterogeneity

Hypothesis 1

Species are continually created over time and without limit; because tropical regions have not experienced glaciation.

Habitats in these areas have had more time to accumulate species.

hypothesis 2

The number of species in an area reflects an equilibrium between the processes of speciation and extinction.

The higher number of species in the tropics is a result of higher speciation rates and lower extinction rates.

Variation in the number of species across a given latitude should also reflect an equilibrium between speciation and extinction.

example of more species where there is greater ecological heterogeneity

While desert vegetation is less productive than marsh vegetation, the greater heterogeneity of the desert landscape provides room for more species of plants.

Among habitats with similar levels of productivity

less heterogeneous habitats will support fewer species

the number of species found in a given location is positively correlated to the amount of

solar energy and precipitation

continental drift

movement of landmasses across Earth's surface

pangaea

the single landmass that existed on earth ~250 Mya and subsequently split into Laurasia and Gondwana

separation of continents allowed species to

independently evolve in different regions of the Earth

joining of continents allowed

groups of organisms unique to one landmass to move into new areas

the separation and joining of continents established

six distinct biogeographic regions that contain unique groups of organisms

example of climate change effects on distribution of plants and animal

When oceans extended from the tropics to polar areas, currents distributed heat more evenly and temperate climates could be found closer to the poles.

Based on fossil evidence, large portions of North America and Europe once had tropical climates that reached into Russia and Canada.

The Antarctic land connection between South America and Australia supported temperate vegetation and abundant animal life.

As Antarctica drifted over the South Pole and as North America and Eurasia encircled the northern polar ocean, the subsequent creation of a circumpolar ocean current around Antarctica caused cooler temperatures at higher latitudes

effects of the Ice Age

Alternating periods of cooling and warming caused the advance and retreat of ice sheets over North America and cycles of cool, dry climates and warm, wet climates in tropics.

The advance and retreat of ice sheets caused the composition of plant species to change as species (e.g., spruce trees) migrated back and forth across the landscape.

where does the water in the Everglades come from?

-rain

\----- rainy summer, dry winter/spring

-Lake Okeechobee

\------rain, spring-fed rivers

where does the soil in the Everglades come from?

bedrock\= limestone

sand\= ancient sand dune

humus\= organic plant debris

Why is the Everglades nutrient poor?

Limestone and sandy soil provides little nutrient except calcium, and high precipitation leaches nutrients from plant litter and is lost through the porous soil

glades

sawgrass\= sedge