Biodiversity & Island Biogeography Flashcards
(49 cards)
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
