Lecture 20 Flashcards
Dark diversity
“set of species that are absent from a study site but present in the surrounding region and potentially able to inhabit particular ecological conditions”
Species pool
all species available that could potentially colonize and inhabit a local area
Extinction debt
“future extinction of species due to events in the past”
Biodiversity hotspot
“Biogeographic region that is characterized by a high level of species richness and endemism”
Species-area relationship (SAR)
Typically number of species increases with increased geographic area
- ALWAYS VIEWED IN LOG-TRANSFORMED SPECIES (continuous linear)
Equilibrium Theory of Island Biogeography
predicts that the number of species on an island is dependent on two factors: the extinction rate and the immigration rate
(incorporates habitat area and isolation)
Steps of equilibrium theory of island biogeography
- New species colonize islands from nearby sources
- As more species colonize fewer species are left to disperse to the island
- Colonization rates slow
Results as species go extinct (4)
- Fewer competitors for resources
- Less niche overlap
- Larger populations for remaining species
- Extinction rate slows
Characteristics of small islands (equilibrium theory of island biogeography)
- fewer resources
- smaller populations that are more vulnerable to go locally extinct
- fewer niches (may have more niche overlap)
When is a species at equilibrium?
When colonization value matches number of species
Alpha diversity
species richness in defined habitat/area
(number of observed species diversity within a defined plot)
Beta diversity
some measure of species differences/turnover of species between habitats
Equation for pairwise beta JI (Jacaards Index)
Intersection of A&B / union of A&B
