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 phyla34 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, World 12,000 marine fish World 4000 reef fish Caribbean 1400 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 SymbiontsHosts Symbiodinium Cyanobacteria Chlorophytes Diatoms Rhodophytes Chrysophytes Algae Ciliates Foraminifera Sponges Cnidaria Flatworms Molluscs Echinoderms Ascidians

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

D IVERSITY Latitudinal diversity patterns

BIOGEOGRAPHIC ZONES Indo- West Pacific (IWP) Western Atlantic Eastern Pacific East 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 VolutidaeCaribachlamys

Species richness -the number of species present in a given area Locally - richness is affected by: Rates of addition of new species Rates of extinction/removal of 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 (> 1m 2 )  richness limited by size of single colonies medium/large (≈ 10 m 2 )  richness affected by habitat heterogeneity very large (> 100 m 2 )  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 ( m 2 )

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)