Carol's biodiversity lectures

Question 1

Reification

Answer 1

Accepting something as if it had empirical evidence when reality it has never been tested;

Abstract terms like biodiversity, ecological integrity, and ecossytem health can sometimes fall into concept of reification

Question 2

Simplest measure of species diversity

Answer 2

Richness

Question 3

The four metrics most commonly used in diversity studies

Answer 3

1) Species richness (univariate)
2) Species diversity (univariate)
3) Species composition (multivariate)
4) Abundance (univariate)

Question 4

Downward bias of species richness

Answer 4

The more we sample, the higher species richness we detect;
However, the relationship is not linear (e.g., species-area curve, species-individuals curve)

Question 5

How to deal with the downward bias of species richness

Answer 5

1) Experimentally standarize sampling area; otherwise site and spatial effects are confounded
2) Rarefing samples

Question 6

Note: trying to standarize species-area by dividing spceis/area doesn’t work

Question 7

Rarefied species richness

Answer 7

Richness of a sample when subsampling a set number of individuals

Question 8

Making a rarefaction cruve (steps)

Answer 8

1) Re-sample a sample a large number of times (~100) and draw curve each time
2) Calculate average curve (smooth curve)

Question 9

Species accumulation curve (its use)

Answer 9

To determine whether enough sampling has been done

(i.e., whether the curve has reached an asymtpote)

Question 10

Species accumulation curve should not be used for…

Answer 10

Comparing different communities. This is because an accumulation curve is only one sampling, and it’s dependent on the order of individuals sampled. Thus, species accumulation curves should be rarified

Question 11

A species accumulation curve can only be used to estimate total number of species when…

Answer 11

species accumulation curve can only be used to estimate total number of species when it reaches an asymptote

Question 12

How to estimate richness when a rarefaction curve has not reached an asymptote

Answer 12

Asymptotic estimators like Chao1 can be used

Chao1:
S_obs = sample richness
f₁ = number of singletons
f₂ = number of doubletons

Question 13

Components of species diversity

Answer 13

Species richness and evenness

Question 14

The two most widely used measures of diversity

Answer 14

Simpson’s and Shannon’s

Question 15

Simpson’s index

Answer 15

D = 1 - Σ(n_i(n_i-1)/N(N-1))

Proability of drawing two species from consecutive sampling

Somewhat biased by the most dominant species

Question 16

Shannon’s index

Answer 16

H’ = -Σp_iln(p_i)

Question 17

Hill’s numbers aka effective numbers of species

Answer 17

Number of equally abundant species necessary to produce the observed value of diversity;

Because they are in the units ‘numbers of species’ values of diversity are comparable across different Hill number metrics;

Because of this Hill’s numbers should always be used

Question 18

Hills’ H’

Answer 18

H’_Hill = exp(H’)

Question 19

Hill’s D

Answer 19

D_Hill = 1/(1-D)

Question 20

How to deal with the downward bias of species diversity

Answer 20

1) Standarize sampleing area
2) Rarefaction can be done for diversity indeces using Hill’s formulae (but is rarely done)