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 (a)

2) Between habitats (b)

3) Regional (g)

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

Chordata; 18%

Echinodermata; 4%

Bryozoa; 2%

Arthropoda; 13%

Annelida; 4%Mollusca; 21%Nematoda; 1%

Platy-helminthes; 8%

Cnidaria; 5%

Porifera; 1%Algae; 7%

Protista; 15%

Others; 1%

Phylum Diversity in Hawaii

FISH DIVERSITY

On coral reefs – about 4000 species (1/3 of all known marine fish)

Indo-Pacific – about 3000 reef fish

British Columbia – 325 marine fish

Indonesia/Philipines/PNG – about 2500 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 HostsSymbiodiniumCyanobacteriaChlorophytes

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)

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

2) Redundancy in guilds

-differences in diversity have little effect

Clipperton Island (eastern Pacific)

800

600

400

200

0

Clipperton

Tropical Eastern Pacific

Richness in shallow water,nearshore fish

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

-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?