BIOL 3070 UNIT 3 EXAM

Species Richness (S)

total # of different species in a community

• how many species are present?

Species Evenness (E)

how equally individuals or biomass are distributed among species

• how equally abundant those species are

What are the two diversity indices?

Richness and Evenness

Relative Abundance (p_i)

proportion of individuals or biomass belonging to species i

p_i = n_i / N

Probability of Interspecific Encounter (PIE)

probability that two randomly selected individuals belong to different species

PIE = N/N-1 * (1-D)

Inverse Simpson’s Diversity

diversity index incorporating both richness and relative abundance

• considers both richness & evenness

• how diverse is the community overall?

1 / D = 1/∑p_i²

Inverse Simpson’s Evenness

measure of how equally species are represented, adjusted for species richness

• how equally abundant are the species, regardless of how many species there are?

• E = 1: perfect evenness

• E closer to 0: lower evenness

α-Diversity

diversity within a single sample or local community

• average # of species per community

β-Diversity

turnover in diversity between samples collected at different places or times

• β = γ / α

γ-Diversity

diversity within ALL samples or a larger region

• total # of unique species across communities

What does a lower β-diversity indicate?

communities share most or all species

What does a higher β-diversity indicate?

communities share different species

What does the species accumulation curve show?

the number of observed species increase as sampling efforts increase

Rarefaction

standardizes species richness comparisons to a common # of sampled individuals

Asymptomatic Estimators

extrapolates from samples to estimate the number of species not yet detected

Latitudinal Gradients of Diversity

geographic pattern in which species diversity is generally higher near the equator and declines toward the poles

Taxonomic Diversity

assumes all pairs of species are equally similar or dissimilar

• diversity is based on species identities

Phylogenetic Diversity

diversity based on evolutionary history and genetic similarity or differences

• Ex: years since divergence or # DNA base changes

Functional Trait Diversity

diversity based on measurable differences in traits between species

• Ex: comparing plant root depth, body size, or leaf mass per area

Biodiversity

the variety of life, including differences in species richness, evenness, species composition, evolutionary history, and functional traits

How much biodiversity exists on earth?

• 4 billion species evolved over earth’s history

• 8 million living plant & animal species

  • 0.5 million plants & 0.1 million vertebrates

• 2 million species described

• 6 million insect species

Why are there so many undescribed species?

scientists cannot directly count every organism on earth, especially small ones

Methods for estimating global species richness:

1. body size — assumes that many species are small & fewer are large

2. extrapolation of direct counts — estimates global richness using species counts from sampled areas

3. slowing rates of species identification — uses the declining discovery rate to estimate how many species remain

Ordovician Extinction

• 86% species lost

• caused by glacial & interglacial episodes, uplift & weathering of Appalachians altering atmospheric & ocean chemistry

Devonian Extinction

• 75% species lost

• caused by global cooling, deep-water anoxia

Permian Extinction

• 96% species lost

• caused by Siberian volcanism, global warming, ocean acidification, deep marine anoxic waters

Triassic Extinction

• 80% species lost

• caused by elevating atmospheric CO2, global warming, calcification in oceans

Cretaceous Extinction

• 76% species lost

• caused by Bolide impact in Yucatan

What drives biodiversity loss?

Direct Drivers:

• land-use and sea-use change

• climate change

• overexploitation

• pollution

• invasive alien species

Indirect Drivers

• production & consumption

• human population dynamics

• governance

• trade

• technology

What is the expert opinion about biodiversity loss?

• top budget priorities should include acquiring unprotected areas and manage protected & unprotected areas

• biodiversity loss is widespread

IUCN estimates of biodiversity loss

25% of 157,000 assessed species are threatened with extinction

IBPES estimates of biodiversity loss

at least 1 million species are threatened with extinction

Ecosystem Ecology

studies the interactions between organisms (biotic) and their physical environment (abiotic) within a specified space and as an integrated space

Ecosystem Functions

include the physiochemical and biological processes that occur within the ecosystem to maintain terrestrial life

Ecosystem Services

the set of ecosystem functions that are directly linked to benefit human well-being

Biodiversity-Ecosystem Functioning (BEF) Relationship

the relationship between biodiversity and the processes performed by ecosystems, such as productivity and nutrient uptake

Overyielding

when a species mixture produces more biomass than expected based on the monoculture yields and proportions of its constituent species

The 3 Sisters

1. Corn: provide structure for beans to climb

2. Beans: works with nitrogen-fixing bacteria, adding nitrogen to soil

3. Squash: shades the soil, keeping it cool, moist, and weed-free

Selection Effect

an increase in ecosystem function because a diverse community is more likely to contain a highly productive or competitively dominant species

• species differ in one limiting resource (R*) can produce overyielding

Complementarity Effect

an increase in ecosystem functioning because different species use resources differently or facilitate one another

• competition for 2 resources can produce overyielding

• can promote coexistence

Temporal Selection Effects

different species contribute most strongly to ecosystem functioning at different times

Spatial Selection Effects

different species contribute most strongly to ecosystem functioning at different locations

Functional Redundancy

multiple species can perform similar ecosystem functions

Redundancy Hypothesis

predicts that adding species initially increases ecosystem functioning, but the benefit of additional species becomes smaller as more species perform similar rates

Ecosystem Services

nature’s contributions to people; all the benefits people obtain from ecosystems

1. supporting

2. regulating

3. provisioning

4. cultural

Supporting Ecosystem Services

services that provide habitats, maintain biodiversity, and form the foundation for other ecosystem services

Regulating Ecosystem Services

benefits from natural processes that regulate environmental conditions, such as climate, water flow, and pollination

Provisioning Ecosystem Services

material goods people obtain from ecosystems, such as food, water, wood, and medicinal resources

Cultural Ecosystem Services

non-material benefits people obtain from ecosystems, including recreation, inspiration, and spiritual experiences

What are current predictions for biodiversity and ecosystem provisioning?

provisioning services are expected to increase while regulating services decrease

What is the Intergovernmental Panel on Climate Change (IPCC)

the United Nations body for assessing the science related to climate change

• Objective: to provide governments at all levels with scientific information that they can use to develop climate change

What is the Intergovernmental Science-Policy Platform on Biodiversity & Ecosystem Services (IPBES)

an independent intergovernmental body

• Objective: to strengthen the science-policy interface for biodiversity and ecosystem services for the conservation and sustainable use of biodiversity, long-term human well-being and sustainable development

Biodiversity-Stability Hypotheses (Elton, May, and McNaughton)

1. Elton: more diverse communities will resist invasion by exotic species and diseases more than depauperate communities

2. May: more diverse communities will be less stable than depauperate communities

3. McNaughton: more diverse plant communities exhibit greater stability of community biomass

Resistance

how much does productivity change during the disturbance

Resilience

How quickly does productivity recover after a disturbance?

Ecosystem Stability

the ability of an ecosystem to maintain consistent functioning over time

• measured as the inverse of variability (1/CV = mean/SD)

Population Stability

how consistently an individual species’ population remains stable over time

Connectance

proportion of possible interspecific interactions that occur

Interaction Strength

mean magnitude of effect of one species’ density on the growth rate of another species

Stable

system returns to equilibrium after small perturbation

Variability

coefficient of variance

• CV = SD/mean of abundance of biomass over time

What is the relationship of resistance and resilience when biodiversity increases?

Higher biodiversity ecosystems show greater resistance while there is no significant relationship with resilience

What is the relationship between species richness/biodiversity and ecosystem & population stability?

More species/biodiversity increases the stability of ecosystems but decreases the stability of populations

3 Biodiversity Mechanisms that Increase Ecosystem Stability:

1. Temporal Insurance Effect

2. Spatial Insurance Effect

3. Interspecific Competition

Synchrony Fluctuations

species fluctuate together

• total biomass fluctuates strongly

• greater community variability

Complementary Fluctuations

species fluctuates offset each other

• when one species increases the other decreases, so total biomass remains relatively stable

• greater community stability

What determines community variability?

1. Synchrony in fluctuations

2. Inequality in fluctuations (amplitude)

3. Structure

CV = temporal sd. / temporal mean

lower CV = higher ecosystem stability