Biodiversity & Island Biogeography Flashcards
when was the term biodiversity coined
1986
how was biodiversity initially defined
“Biological diversity“ means the
variability among living organisms from all sources … and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.
define species diversity
number of species present
define species density
number of species per area
define species evenness
Degree of equality in the
distribution
(Pielou 1975)
maximum evenness = all species have the same number of individuals (same cover, biomass, etc.) in a given area
define alpha diversity
richness of the community in number of species
define beta diversity
extent of species replacement or biotic change along environmental gradients
define gamma diversity
richness in species of a range of habitats (a landscape, a geographic area, an island),
who came up with alpha beta and gamma diversity
whittaker 1972
list the 8 biomes
tundra, taiga, steppe & cold desert, temperate deciduous forests mediterranean shrubland, hot desert, tropical grasslands and savannah, tropical rainforest
5 ways to express alpha diversity
1) the number of species
2) Berger-Parker-Index (Dominance)
3) Simpson‘s Index
4) Fisher‘s alpha
5) The Shannon-Wienert (-Wiener /-Weaver) Index
what is the idea behind the berger-parker index
What is the proportion of the most dominant species in the sample?
so, the greatest value indicates equal distribution
what is the idea behind Simpson’s index
Probability that two individuals drawn from the
same population represent the same species
so, the greatest value indicates equal distribution
advantages and disadvantages of recording a diversity by counting number of species
Advantage: Very easy to use and understand
Disadvantages: Does not consider ABUNDANCE of species, mostly NOT applicable for mobile organisms
advantages and disadvantages of berger-parker index
Advantage: extremely easy to calculate and to interpret, often works astonishingly well
Disadvantages: heavily influenced ONLY by the most dominant species, species number has no influence
advantages and disadvantages of simpson’s index
Advantage: Widely used
Disadvantage: Strongly influenced by distribution pattern
advantages and disadvantages of fisher’s alpha
Advantage: Very widespread, independent of sample size for larger N (and/or low overall diversity)
Disadvantages: Difficult to calculate (parametrical index, empirical approach), theoretical prerequisite: log-series distribution
advantages and disadvantages of shannon-wienert index
Advantage: Widely used (comparisons!)
Disadvantage: Generally considered as rather unsuitable!
what is the latitudinal gradient of species diversity
General tendency for diversity to increase towards the tropics
how does a site’s primary productivity effect it’s species diversity
more species at more productive sites
How do species numbers develop on islands with former land-bridge connections?
On formerly connected islands, species diversity decreases over time, until an equilibrium is reached, as can be seen for the species diversity of lizards on former land-bridge islands in relation to time since isolation.
what is the key factor determining number of species on an island
island area (size)
are - diversity pattern
how can alpha and beta diversity be used to find gamma diversity
a*b=y or sometimes a+b=y
advantages and disadvantages of using alpha diversity
ADV: easy to use and understand
DISADV: doesn’t account for abundance, not applicable to moving organisms
how to calculate berger parker index
1/(number of individuals of most common species/total number of individuals)
how to calculate simpsons index
1- (SUM all species ((no of individuals of a species/no of individuals)^2))
how to calculate fishers alpha
species number = alpha term * log (1+ (total no of individuals/ alpha term))
what are the flaws in species knowledge and sampling
very partial (most species have not been described), inaccurate (taxonomy errors), biased )v western)
how many known species
1.9m
describe the global gradient of species diversity
latitudinal, with more diversity near the tropics and less near the poles
reference for latitudinal gradient of sp. Div.
cox and moore 2000
which factor could be argued to explain the latitudinal gradient of species diversity
positive relationship between potential evapotranspiration and species
how much variation is there to the number of birds on an island
v stable equilibrium
what determines the number of species that can live on an island
the area of the island - amount of space available
formula to express how many species can live on an island
“S=CA^Z
S = no of species
C = constant representing expected diversity
A = Island area
S= slope parameter when S and A are plotted logarythmically”
which 2 population forces balance to create the equilibrium of species on an island
immigration of new species and extinction of old species. The point at which they intersect is the equilibrium
which species can colonise remote islands
bats, landbirds, insects and molluscs can cross ocean gaps over 2000 miles, lizards can do 1000 miles, tortoises and rodents 500 etc
why could species good at dispersing to different remote islands be bad colonizers
they could easily be blown away from the remote area e.g. birds
why do flightless birds develop on islands
allows them to colonize the island and remain on it easier
how does island size impact the number of species that can live there
more extinction on small islands
which factors affect immigration/colonization rate
isolation of the island - bigger immigration pool if there are other islands/land nearby
main 2 drivers of the species richness equilibrium
area and isolation
how valid are observations on islands for closed off conservation areas (effectively enforced islands)
visible saturation ccurve, so to some degree terrestrial islands are have similar driving factors
reading for island biogeography theory
gorman 1979
how is diversity impacted if an island had a former land bridge connection to mainland
higher species diversity, but decreases over time in relation to time since isolation
how fast do newly isolated islands take to reach species equilibrium
varies by size, but up to 20k yrs for birds, 30k yrs for lizards
factors impacting time taken for newly isolated island to reach equilibrium
island size, taxonomic group in question, habitat requirements
what can data about species richness loss in newly created islands tell us about nature reserve design
needs as large area as possible, one large habitat is better than many smaller habitats with same total area. If needed due to predators, keep them enar each other. keep source area nearby (not too isolated), try and create corridors to source area
when may isolation be useful in nature reserves
protecting from predation e.g endangered european tree frog eats all endangered great crested newt tadpoles
