diversity on coral reefs. diversity - perspectives 1) taxonomic 2) ecological 3) genetic 4)...
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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)