Anne Bjorkman - Biodiversity Flashcards
Biodiversity
The number of different biological variants found in a given place and time. Communities vary in species number (species richness) and species composition (which species).
Shannon index
A common way to measure diversity. A combination of the number of individuals in the species and the number of species in the community.
Genetic diversity
The amount of genetic variation within a species.
Species diversity
Number and evenness of different species.
Functional diversity
Variation among the traits or functions of species or individuals in a community.
Functional traits
Different characteristics of organisms. Can be body size, rooting depth, seed size, and so on.
Same number of species but different diversity?
Using species richness as our metric treats all species as equally different, even though some may do basically the same thing.
Using functional traits instead better reflects which species have different functions, and shows diversity in a better way. We look at their traits and how they function in their community.
Factors influencing diversity on a global scale
Five hypotheses.
More sun close to the equator, leading to more mutations.
Less extinction.
Factors influencing diversity local scale
Intermediate disturbance hypothesis: at intermediate levels of disturbance, there should be the highest diversity.
Heterogeneity: variation in many different factors. More variation leads to higher diversity.
Area: bigger area leads to higher diversity.
Isolation: islands show a pattern of fewer species with distance from the source.
Island diversity
More diversity on a bigger island closer to the mainland. Dispersal ability of the species also matters.
Why do smaller, isolated islands have less diversity?
They can sustain fewer individuals of each species due to lack of resources, and they are therefore more likely to go extinct.
Less environmental heterogenity.
Large islands can support species with large range sizes.
Less gene input, more inbreeding, leading to greater risk of extinction. New species wont reach the island, extinct species will not be replaced.
Theory of island biogeography
The number of species on an island depends on the balance of immigration and extinction. Predicts the number of species, but not that the composition remains constant. Changes in composition over time is called temporal turnover.
Most diversity
Large, near
Small, near
Large, far
Small, far
Least diversity
Important for conservation.
Turnover
Species richness remains relatively constant, but composition changes. Only islands?
Practical uses for equilibrium theory of island biogeography
Humans are fragmenting many biomes on earth. Small, isolated patches of suitable habitat surrounded by extensive areas of unsuitable habitats. Understanding how size and isolation influences diversity can help us conserve and restore diversity in human-modified areas.
Edge effect
Edges of the fragmented biomes are much less hospitable, thus reducing the effective size of the fragment. The edges are too different from the original habitat. It doesn’t always mean that the total diversity is lower, but the desired species/habitat are negatively affected.
Patch shape matters, squares are better than rectangles.
