lec 17- patterns of species diversity Flashcards
what is the latitudinal pattern of species diversity?
latitudinal- species increase when going from pole to equator, global patterns
what are metapopulations?
-modern extension of island biogeography, group of spacially separated populations of same species
what other things influence diversity?
evolutionalry history, habitat heterogenity, species interactions etc.
what causes latitudinal diversity gradients?
Time: time since glaciation/major disturbance, which resets diversity and climate stability = more diversification
Area: global land area dominated by tropics
energy: solar input higher, more productivity could allow more species to coexist
what are the exceptions to the increased diversification?
animals that live at poles, like penguins
what are global biodiversity hotspots?
regions with large amounts of diversity in species
how many global hotspots are in the world?
34
what do the global hotspots contain?
-50% of endemic plants
-42% of worlds vertebrate endemics
-77% of all terrestrial vertebrates
-2.3% of earths land surface
what are endemic species?
species only present in one area
do bigger islands have more species?
yes, the larger the island the larger the number of species
what is the formula for species-area curves?
S = c x A^z
S = number of species in island/habitat
A = area of island/habitat
c = constant
z = slope (another constant)
z for islands = 0.32
z for continents = 0.17
what determines island richness?
colonization and extinction rates
(number of species/time)
why does species richness increase with island size?
more habitats to support more species, less extinction
why does species richness decrease with isolation?
less likely to be colonized
what type of island has a higher chance for extinction?
smaller islands
what islands have more colonization?
closer islands
how was island biogeography tested and what was found out?
Defaunation experiment:
-survey small mangrove islands for arthropods
-cover island with plastic and spray pesticides (get rid of arthropods)
-observe colonization/succession over one year
Results: species richness returned to the same levels before defaunation, closer large islands had more species, supported dynamic equilibrium
what determines the proportion of sites occupied for metapopulations?
-colonization and extinction rates at each site
-connected by individual movement
-sites can be colonized one year then extinct the next
-variable, but the sites are usually stable
what are the two dynamic equilibrium theories?
island biogeography: predicts equilibrium of species in an area
metapopulation: predicts equilibrium proportion of sites occupied by a species
what are characteristics of classic metapopulation?
-fixed rates of colonization and extinction
-subpopulations have independent dynamics and are connected by dispersal
-all patches of identical quality (not realistic)
what is lesson 1 of classic metapopulation?
unoccupied patches can be rescued by immigration from other patches (rescue effect)
what is lesson 2 of classic metapopulation?
unoccupied patches are necessary for metapopulation persistence
what is mainland metapopulation?
1 area persists indefinitely (mainland) and provides colonists to other areas that go extinct, differences in patch quality
what is source sink metapopulation?
sources have increased population growth, while sinks have low population growth so colonists from source are provided to sinks, differences in patch quality
