drivers of biodiversity

species-area relationship ( SAR)

richness increases with area- SIMILAR REGARDLESS OF ECOSYSTEM OR BIOME

• greater diversity of habitat = more rare species - are more likely in area

• intercept = ALPHA

• shape of curve = beta

main theories on why does richness decrease with latitude

• productivity richness hypothesis

• ambient energy hypothesis

other reasons why richness may decrease with latittude

• climate harness= more difficult at high latitudes

• climate stablity= more resource availbity

• historical perturbation- tropics = longer time since glaciation= time for specieaion

• geogrpahical hypothesis - tropics biomes larger than north

productivty richness hypothesis

higher productivity increases diversity

• hump shaped relationship

  • SR increase with prod up to certain point then decreases

ambient energy hyptohesis

less solar energy available in higher latitudes= less ideal range for physiology which limits productivity

forces producing diversity in trees and other plants

• fine- scale variablity ( niche assembly)

• ecotones -boundry btwn 2 ecosystems

• producitvity

• disturbance

• historical events - disturbances, glaciation

forces producing diversity in animals

• at continental sclae = plant diversity

• at local scale = tree height- wide arraw of niche spaces

• competition and richness

• island biogeography

how does fine scale variablity produce diversity in trees

micro-tophography and gaps and logs , affects

• water and nutrient avialtiy in soil

• affects storage or legacies

• time ( sucession)

how does ecotone produce diversity in trees

has unique combo of species: new species, high diversity, rare species

• zone of migrations and energy flows across boundaries- has overlap of species

• zone of rapid change and complex feedback

producitivty in trees in BC

more in coast, less in middle because dryness

how does disturbance produce diveristy in treees

int. disturbance hypothesis

• no disturbaces= 1 speices domiantes

• lots of disturbance = early sucessional species dominates

• mixed = no dominateion, early, mid and late sucessional speceis

seastar example

low in BM but drives ecosystem diversity by regulating abundant species

• richness is density dependnet and seastars would eat species that were more abundant

• regulating the population of other organisms

keystone species

a species that can strongly influecne an ecosytem even if it has low abundance

when can a predator mediate prey co-existence

if predator has prey prferences that are density dependnet

island biogeography affect on animal diversity- distance from aminland

affects immigration rate/ colonization

• close = more frequent species arrivals

• far= less frequent arrivals

island biogeography affect on animal diversity- size of islands

affects rate of extinction

• small= less resources= harder to survive

• large= more habitat and diverse resources = easier to survive