Lecture 22: Biogeography Flashcards
Biogeography
Study of the variation in species composition and diversity among geographic locations
Species richness and composition tend to vary with _______
latititude
Where has higher diversity?
Tropics
Species richness and composition vary from ____ even where latitude is roughly similar
continent to continent
3 Categories of Hypotheses for why tropics are so diverse?
Diversification rate
Diversification time
Productivity or carrying capacity
Diversification rate Hypothesis
Species diversification rate is higher in the tropics (then temperate)
Tropics have larger land area more stable temperatures than temperate region
Diversification rate Hypothesis: tropic as cradle, museum, or destination?
High speciation rates
Tropics are a cradle of diversity (tropics are where species tend to be born)
Diversification time Hypothesis
Diversification rates are similar but evolutionary time is greater in the tropics
Tropics have spent much longer since their last glaciation allowing more time for diversification
Diversification time Hypothesis: tropic as cradle, museum, or destination?
Low extinction rates
Tropics are museum of diversity; tropics tend to have old species that in other parts of the world would go extinct
Productivity or carrying capacity Hypothesis
Higher productivity results in more abundant resources in the tropics
Without winter, growing seasons are twice as long
Plants are more productive
Trees are bigger and potentially provide more niches for other species
Productivity or carrying capacity: tropic as cradle, museum, or destination?
High immigration rates
Tropics are destination
Place where species that originated in other places end up invading and accumulating
Tropical vs extratropical taxa origin (all extant and extinct bivalves)
Increase taxa in tropics
Extant bivalves show
present distribution of taxa of tropical origin
As with most things in ecology, “diversity” is higher in tropics” is not an
absolute truth
Major biogeographic patterns
Species richness and composition tend to vary with latitude (tropics have higher diversity)
Species richness and composition vary from continent to continent, even when latitude is roughly similar
The same community type of biome can vary in species and composition depending on its location on Earth
Wallace identified 6 biogeographic regions using ___ and 6 regions roughly correspond to _____
distributions of terrestrial animals
Earth’s major tectonic plates
Vicariance
The geographical
separation of a population, typically
by a physical barrier such as a
mountain range or river, resulting in
a pair of closely related species.
Global species diversity
all species that are currently present on Earth
Regional species diversity
all species with the
possibility of inhabiting the
local scale. Area connected
enough for dispersal of species
and roughly similar climate
Local species diversity
area of interest,
where individuals are
interacting (think
ecological population
definition for many
competing species)
Local community as result of many
filters
To get from regional species pool to local community: filters in order include
Dispersal or immigration
Abiotic factors
Species interactions
γ diversity
Regional species pool
α diversity
Local diversity
β diversity
Species turnover
Species composition measures B diversity (species turnover) which is
the number of species that are lost + the number of species
gained by moving from one local community to the next.
= (αA – common species) + (αB -
common species)
Equal regional richness to local richness
all species get everywhere
Proportional change to regional richness
Regional control of species
Asymptotic change to regional richness
Some carrying capacity for species, local control
Species richness increases when we increase
scale of the sampling area
Species area curve
The number of species increases with area sampled
Does not stop because you start to encompass other types of habitats
z for species area curve between
.2 and .35
bigger z value for species area curve means
greater the β diversity.
That is, if
the turnover is greater, the differences among local sites are
greater.
