Day 18 - Measuring Biodiversity

What are the 4 types of biodiversity?

1. Genetic Diversity

2. Species Diversity

3. Functional Diversity

4. Landscape Biodiversity

What is landscape biodiversity?

The number/arrangement of specific habitat types or ecosystems

Why is genetic diversity important?

Higher genetic diversity usually indicates strong species persistence

More genetic diversity = more resilience

Why is species diversity important?

Higher species count can mean more stable and resilient community

What you normally think of when hearing biodiversity

What is functional diversity?

The diversity of ecological roles, not just species

Lots of different minnow but all have the same function = low functional diveristy

Why is functional diversity important?

More applied

Can be more indicative of stability/resilience

What is richness?

The raw number of species in a community

What is evenness?

The evenness of abundance between species in a community

Is one species dominant over the others?

What is the richness for each community?

Community A = 4

Community B = 4

Which community is more even?

Community A

What is alpha diversity?

The diversity of species within a single habitat

What does a higher alpha diversity indicate?

A higher diversity

What is beta diversity?

The diversity of species between habitats/species turnover

When each patch is distinct = higher beta (each patch has different species)

What does a higher beta diversity indicate?

Higher diversity

What is gamma diversity?

The diversity of species across all habitats of interest

What does a higher gamma diversity indicate?

Higher diversity

What are the 4 main ways to measure diversity?

1. Count individuals in an area

   1. How much effort should you put in?

   2. How do you handle rare species?

2. Stratify by habitat

   1. Dedicate time in riffles, runs, pools

3. Rank abundance curves

   1. Made after collecting data

4. Log abundance plots

   1. Creates a normal distribution

What does this graph show?

A Rank Abundance Curve

What does this graph show?

A Log Abundance Plot

What would the rank abundance curve/log abundance curve look like if the community was richer?

The log plot would get taller and wider

The rank plot would get wider

What would the rank abundance curve/log abundance curve look like if the community was more even?

Rank would be flatter

Log would also be flatter

What does being rare mean?

Limited geographic range

Specific habitat requirements

Locally sparse population

How can rarity affect measuring biodiversity?

Complicate single estimations and comparisons across locations

Certainly, going to miss species when sampling

What are the 2 ways to estimate missing species?

1. Rarefaction Curves

2. Chao’s Indicator

What is a rarefaction curve?

Mathematically estimate asymptote of accumulation curve

What is a drawback to a rarefaction curve?

You are likely to be wrong if you already don’t have a good sample

What does this graph show?

A rarefaction curve!

Most of the species caught in the first few sample runs

Lots of errors between the lines

What does this equation show and what do the parts mean?

Chao’s Indicator

• Sest = estimated species

• Sobs = samples species

• a = number of species with only 1 individual

• b = number of species with 2 individuals

What is a Chao’s indicator?

A conservative estimate

Best used with the rarefaction curve

What is a drawback to a Chao’s indicator?

Samples will usually be lower than reality

What are the 2 diversity indices used?

1. Shannon Diversity Index

2. Simpson Index

What equation is this?

The Shannon Diversity Index

s = number of species in your community

pi = proportion of species i that show up (i/total number of species in your community)

What equation is this?

The Simpsons Index

s = total individual in community

pi = proportion of species i out of total

What are diversity indices good for?

Taking richness and evenness and putting it all into 1 number

What are pros to diversity indices?

Can combine species richness and evenness into one value

Relatively easy to calculate

Many indices with their own respective usefulness

What are cons to diversity indices?

Each index has its own quirks and sensitivities to be aware of

Comparison among sites using indices not very meaningful (especially statistically)