Conservation Bio Exam 1-Module 2

5 applications of biodiversity metrics

Quantify types of diversity, compare diversity across scales, monitor effects of interventions, analyze relationships, inform action

What is another name for diversity metrics

Diversity indices

Species richness (S or R)

Number of species in an area, all species weighted equally

What is species richness greatly affected by

Sampling area or effort

Common ways to standardize samples for comparison

Sample equal area or equal number of individuals

Does diversity increase or decrease with habitat area

Increase

Species-accumulation or species-area curve

Number of species vs sampling effort

Asymptote on a species-area curve

True total richness of a site

Alpha diversity

Species diversity within a site, single community, or geographic area

How far can richness be extrapolated

2x sample size

When should asymptotic richness be estimated (3)

Curve is already leveling off, sample coverage is high so most individuals are species already sampled, species to compare are approximately equal

Gamma diversity

Total diversity across multiple communities or geographic areas

Beta diversity

Turnover (dissimilarity) between two or more communities

What is average alpha, gamma, and beta

3, 4, 1.33

Species diversity equation

Beta=gamma/alpha or alpha x beta=gamma

What does a Beta=1 mean

Two communities are the same as one community (no turnover)

What do diversity metrics based on species richness not account for

Differences in species proportions or relative abundance

Evenness

How similar the proportions are of each species based on their relative abundance

When is diversity maximized

All species are equally abundant (=R)

Rank-abundance curve

Sort species by proportional abundance, plot abundance vs rank or species ID

Which communities are the most diverse

Perfectly even communities with the greatest richness

Why use a diversity Index (3)

Synthesizes complex community data, combines richness and evenness, enables standardized comparisons between 2 or more communities

Shannon index of diversity

Weights species by their relative abundances to account for evenness, a measure of entropy

Entropy

Uncertainty in identity of randomly selected individual

When is entropy maximized

Many species with equal abundances

When is entropy minimized

All individuals belong to once species

Cons of shannon index of diversity (3)

Difficult to interpret, doesn’t obey mathematical rules, unintuitive

Hill’s numbers

Effective number of species (number of species the sample would have if all species were equally abundant

R

Count of all species present

Hills numbers: what is D when q=0

Species richness (R)

q=0 for species proportions

All species given equal weight (relative abundance not considered)

q=1 for species proportions

Rare and common species are weighted by their proportiona; abundance

0<q<1 for species proportions

Rare species are given greater weight

q>1 for species proportions

Rare species are discounted (given less weight)

What do species accumulation curves show

Number of species as sampling effort increases

Options for comparing diversity across two or more communities (2)

Standardize unequal sample sizes by number of samples or standardize samples by coverage/how representative they are of the whole community

Problem with standardizing by number of samples

Can result in loss of information from larger samples

How to standardize by number of samples

Interpolation/rarefaction of larger samples

Solution to problem of standardizing by number of samples

Extrapolate the smaller samples, but only up to 2n

Coverage

Proportion of the total number of individuals in a community that belong to the species represented in the sample