ch 22 : landscape ecology, biogeography, and global biodiversity Flashcards
the field of study that considers the spatial arrangement of habitats at different scales and examines how they influence individuals, populations, communities, and ecosystems
landscape ecology
current habitat heterogeneity is a reflection of what?
recent and historical events caused by natural human forces
long-lasting influence of historical processes on the current ecology of an area.
legacy effects
what can continue to cause habitat heterogeneity?
natural forces
how has human activity influenced natural forces?
human activity has influenced the intensity, frequency, and ecological influence of natural forces.
why does species richness often increase from the local to landscape scale?
because habitat diversity increases along this gradient
the number of species in a relatively small area of homogenous habitat, such as a stream
local (i.e. alpha) diversity
the number of species in all of the habitats that comprise a large geographic area
regional (i.e. gamma) diversity
the number of species that differ in occurrence between two habitats
beta diversity
the collection of species that occurs within a region; serves a source of species of all local sites within a region
regional species pool
the process of sorting species in the regional pool among localities according to their adaptations and interactions
species sorting
a graphical relationship in which increases in area (A) are associated with increases in the number of species (S)
species area curve
equation for species-area curve
S = cA^z where c and z are constants fitted to the data
or
log S = log c + z log A
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.
slide 12 !!
what have human activities caused throughout the world?
widespread fragmentation of large habitats
what are the effects of fragmentation?
- it decreases habitat area and increases patch number, edge size, and isolation
- small habitats have small populations which are more likely to go extinct
specifically, how does fragmentation effect fragment edges?
- fragmentation causes an increase in the amount of edge habitat compared to the original unfragmented habitat
- an increase in edge habitat changes the abiotic conditions (e.g., ground temperatures in a forest) and the species composition of a habitat.
what happens to species that prefer edge habitats when fragmentation occurs?
they increase in abundance
how can declining populations in habitat patches be sustained?
by the dispersal of organisms between patches via habitat corridors
how do habitat corridors help declining populations?
they increase gene flow and genetic diversity
what purposes can habitat corridors serve?
- pieces of preserved habitats
- constructed for the specific purpose of allowing species dispersal
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
stepping stones
what can help determine whether organisms can move between fragments?
the quality of habitat between fragments (i.e. matrix habitat)
are all habitats in the matrix the same?
no; some habitats in the matrix may contain favorable conditions for dispersal, whereas others might be inhospitable.
CONCEPT : the equilibrium theory of island biogeography incorporates both _____ and ________
area and isolation
what did MacArthur and Wilson find?
- species richness increases with island area
- islands closer to the mainland appeared to receive more colonizing species
how did MacArthur and Wilson test their hypothesis? what did they find?
- to test the hypothesis that species richness is determined by both island area and isolation, they measured bird species richness on
25 islands in the South Pacific. - they found that larger islands contained more species
- among islands of similar sizes, near islands contained more bird species than far islands
t/f the effects of patch size and isolation are very different across multiple types of habitat
false, they are similar
Daniel S and E.O Wilson’s experiment
- 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.
what did Daniel S and E.O Wilson’s experiment result in?
they found that more insects recolonized islands closer to the mainland, and species richness of islands was similar to values before fumigation.
a theory stating that the number of species on an island reflects a balance between the colonization of new species and the extinction of existing species.
equilibrium theory of island biogeography
according to the equilibrium theory of island biogeography, what would happen on an uninhabited island?
many species from a nearby source habitat (e.g. mainland) could potentially colonize the island
assuming the species pool of potential colonizers is a fixed size, what could be said about the rate of new species colonizing the island?
the rate of new species colonizing the island declines as a function of how many species have already colonized the island
what happens as more species colonize the island?
more species are subject to possible extinction due to change and negative interactions (e.g. competition, predation, parasitism)
given that the island continues to experience colonization and extinction of species, what would the opposing forces result in?
these opposing forces should result in an equilibrium point of species richness on the island Ŝ.
theory of island biogeography: this model only predicts what?
- this model only predicts the number of species at equilibrium—not the species composition at equilibrium.
- at equilibrium, there is a continuous turnover of species, resulting in a temporally variable species composition.
theory of island biogeography : smaller islands should have________ extinction rates; islands nearer to a source habitat should have ________ colonization rates.
higher; higher
what reveals predictions regarding Ŝ?
combining the effects of island area and isolation
understanding the effects of what has helped to design nature reserves?
island size and shape
since large areas can support large populations with low extinction rates, setting aside a single, _________ will better protect biodiversity than will several small areas.
large area
what are some other things that need to be considered when designing nature reserves?
- 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.
_________ _______ in diversity are pervasive and extend even to the oceans
latitudinal trends
in the Northern Hemisphere, species richness of most animal and plant groups increase from __________ to _________
north to south
in what direction does mammal species richness increase
mammal species richness also increases to the west, likely due to the habitat heterogeneity of mountains
oceans also have increased species richness at _________ ________
lower latitudes
at any given latitude, there are________ species where there is a greater ecological heterogeneity
more
among habitats with _________ __________ ______ ___________, less heterogeneous habitats will support fewer species.
similar levels of productivity
what rose in response to past environmental conditions?
current diversity
movement of landmasses across Earth’s surface
continental drift
the single landmass that existed on Earth ~250 Mya and subsequently split into Laurasia and Gondwana
pangaea
the northern landmass that separated from Pangaea ~150 Mya and subsequently split into North America, Europe, and Asia
laurasia
the southern landmass that separated from Pangaea and split into South America, Africa, Antarctica, and India
gondwana
what did the separation of continents allow species to do?
independently evolve in different regions of the Earth; the joining of continents allowed groups of organisms unique to one landmass to move into new areas
what did the separation and joining of continents establish?
six distinct biogeographic regions that contain unique groups of organisms
over the past 250 million years, what have the climates on earth experienced?
- dramatic changes as the continents drifted
- these changes have had profound effects on the distributions of plants and animals
about 2 Mya, gradual cooling of the Earth produced oscillations in climate known as the _______ _______
Ice Age
what did alternating periods of cooling and warming cause?
the advance and retreat of ice sheets over north America and cycles of cool, dry climates and warm, wet climates in the tropics
what did the advance and retreats of ice sheets cause?
the composition of plant species to change as species migrated back and forth across the landscape
