DIVERSITY ON CORAL REEFS

DIVERSITY - PERSPECTIVES

1) taxonomic

2) ecological

3) genetic

4) functional

DIVERSITY – WHAT IS IT?

1) Number of taxa (=richness)

2) Measure of evenness in abundance

N species equally common > N species of unequal abundance

DIVERSITY ≈ RICHNESS

DIVERSITY – Spatial Scales

1) Within habitat ()

2) Between habitats ()

3) Regional (

DIVERSITY – Phylogenetic Scales

-diversity can depend on the taxonomic level

species

phylum

>

<

DIVERSITY – Phylogenetic Scales

Number of animal phyla 34

Number that are solely marine

17

Number with both marine a and non-marine members

16

Number that are solely non-marine (terrestrial)

1

33 of 34 phyla represented in marine biome

Phylum Diversity in Hawaii

Recognition of how many species there are

FISH DIVERSITY

Indo-Pacific 3000 reef fish

British Columbia 325 marine fish

Indonesia/Philipines/PNG 2500 reef fish

12,000

6, 000

0

World12,000

marine fish

World4000 reef fish

Caribbean1400 reef fish

Why are coral reef environments so diverse?

1) Environmental favourability

2) Productivity

3) Habitat heterogeneity

4) Niche diversity

5) Niche breadth

6) Interspecific interactions

7) Evolutionary processes

- Historical stability

- Speciation rates

- Extinction rates

Diversity in reef ecosystems(How does diversity affect ecosystem function?)

1) Photosymbioses

Symbionts Hosts

SymbiodiniumCyanobacteriaChlorophytes

DiatomsRhodophytesChrysophytes

AlgaeCiliates

ForaminiferaSpongesCnidaria

FlatwormsMolluscs

EchinodermsAscidians

Diversity in reef ecosystems(How does diversity affect ecosystem function?)

2) Redundancy in guilds

-differences in diversity have little effect

Clipperton Island (eastern Pacific)

Redundancy in guilds

No differences in reef structure

DIVERSITY

Latitudinal diversity patterns

BIOGEOGRAPHIC ZONES

Indo- West Pacific (IWP)

Western AtlanticEastern

PacificEast Atlantic

BIOGEOGRAPHIC ZONES

Paleontological/Tectonic Factors

Early Cretaceous

Tethys Sea

Seafloor spreading widens Atlantic

Movement of Africa separates Indian Ocean and EA

Isthmus of Panama emerges and separates WA and EP

Separation of bioregions – What are the effects on fauna?

1. Western Atlantic

-Cenozoic extinctions

-extinctions associated with the closing of the Isthmus of Panama

Separation of bioregions – What are the effects on fauna?

2. Eastern Pacific

-fauna of Florida and California - similar

-extinctions associated with the closing of the Isthmus of Panama

Separation of bioregions – What are the effects on fauna?

3. Eastern Atlantic

-extinctions associated with the closing of the Tethys seaway

-can happen via:

Speciation

1) Vicariance event

Species A + B + C

Species C

Species B

Species A

-can happen via:

Speciation

2) Founder event (Bottleneck)

Small genetic diversity

bottleneck

Large genetic diversity

Time

-can happen via:

Speciation

2) Founder event (Bottleneck)

Role of the Indo-West Pacific Bioregion

Centre of diversification?

Role of the Indo-West Pacific Bioregion

Hydrodynamic sink?

What about the Caribbean?

extinctions

Volutidae Caribachlamys

Species richness

-the number of species present in a given area

Locally - richness is affected by:

Rates of additionof new species

Rates of extinction/removalof existing species

Richness

(Rate = total number of species / unit time

Species richness

Affected by:

• Area

• Productivity and light

• Disturbance

• History/Biogeography ✔

Area

Habitat area

Richness

Why?

1. Larger habitats are larger targets for dispersing organisms

2. Larger habitats contain more diverse microhabitats

3. Larger habitats support larger populations which have lower rates of local extinction

Area

Problems:

1. Measure of richness sampling unit

2. Corals take up substrate space so that richness may be limited by average colony size

3. If sampling unit is small (> 1m2) richness limited by size of single colonies

medium/large (≈ 10 m2) richness affected by habitat heterogeneity

very large (> 100 m2) richness between habitat heterogeneity

Area

Anthropogenic Effects

Productivity and Light

Energy available - limits richness

Energy available

Richness

Productivity and Light

On reefs - relationship is not clear

Energy available

Richness

Energy available

Richness

Large scale(regional/oceanic)

Small scale(10 - 100 m2)

Productivity and Light

Depth

Distance from shore

Decreasing light

Decreasing turbidity

Trend to heterotrophy

Increasing polyp size

Richness

Competition

Disturbance and Richness

-disturbance more variable than productivity

Disturbance

Depth

Summary

Shoreline

- frequent low level disturbance

- bright light but more turbid

Forereef

- less disturbance

- bright light and less turbid

- increased competition

Deeper forereef

- little disturbance

- lower light and little turbidity

- decreased reliance on symbionts

-more heterotrophic corals (but decline in abundance of plankton)