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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 (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 Phylum Diversity in Hawaii Others 1% Protista 15% Chordata 18% Echinodermata 4% Algae 7% Bryozoa 2% Porifera 1% Cnidaria 5% Arthropoda 13% Platyhelminthes 8% Nematoda 1% Mollusca 21% Annelida 4% FISH DIVERSITY On coral reefs – about 4000 species (1/3 of all known marine fish) Indo-Pacific – about 3000 reef fish Indonesia/Philipines/PNG – about 2500 reef fish British Columbia – 325 marine 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 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) 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 Richness in shallow water, nearshore fish 0 Tropical Eastern Pacific Clipperton Redundancy in guilds No differences in reef structure Latitudinal diversity patterns DIVERSITY BIOGEOGRAPHIC ZONES Eastern Pacific East Atlantic Indo- West Pacific (IWP) Western 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 -extinctions associated with the closing of the Isthmus of Panama -fauna of Florida and California - similar Separation of bioregions – What are the effects on fauna? 3. Eastern Atlantic -extinctions associated with the closing of the Tethys seaway Speciation -can happen via: 1) Vicariance event Species C Species A Species B Species A + B + C Speciation -can happen via: 2) Founder event (Bottleneck) Small genetic diversity bottleneck Large genetic diversity Speciation -can happen via: 2) Founder event (Bottleneck) Role of the Indo-West Pacific Bioregion Centre of diversification? Role of the Indo-West Pacific Bioregion Hydrodynamic sink?
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