Evolution of reef habitats: co-evolution of fish and corals Flashcards
(21 cards)
What is a function? Who defined this?
The movement or storage of energy or material (as defined by fish ecologists)
How do reef fish perform functions?
Typically involved in the movement of energy and material via:
- Consumption
- Movement
- Waste release
How do corals perform functions?
Typically associated with energy storage.
Summarise quickly reefs up to the end of the Permian.
Cambrian -> Archaeocyathids reefs
Ordovician/Silurian -> rugose and tabulate corals
End of the Permian -> mass extinction wiped out rugose and tabulate corals, allowing scleractinians to dominate reefs.
How many major phases of reef fish evolution are there? Which papers are these in?
Six -> Bellwood et al. (2015) and Bellwood et al. (2017)
Summarise phase 1 of reef fish evolution.
Fish diversity aligns with coral diversity but there is little interaction between the fishes and the reefs/corals.
This is largely due to long thin jaws, which allowed them to bite other fishes but not bite the seabed.
Main interactions were one-way, from fish to reef via defecation and decomposition, for example.
Which geological periods did phase 1 of reef fish evolution cover and what is associated with these?
Up to the Permian.
Within this, the Devonian was referred to as the “Age of fishes” due to the high number of broad groups. This reflects the high diversity but limited reef-fish interaction.
What did the Permian mass extinction cause?
The extinction of the trilobites and rugose/tabulate corals.
Which phase of reef fish evolution followed the Permian mass extinction?
Phase 2
Summarise phase 2 of reef fish evolution.
Took a little while for evolutionary roots to regrow, but was associated with new trait emergence.
New traits included short, deep jaws (opposite to thin jaws) with slow closing ability -> capable of consuming the seabed and interacting with reef systems.
What were the major fish group called in Phase 2 of reef fish evolution?
The Pycnodontiforms (flourishing during the Jurassic).
These had deep bodies for manoeuvering around benthic structures, as well as strong jaws for seabed consumption.
What is durophagy? What morphological adaptations are associated with this in reef fishes.
A functional adaptation to eating hard or tough food. This involved:
- Flattened molars for crushing shells
- Incisive teeth for cutting algae
- Deep body forms for agile movement around reef structures
When does Phase 3 begin?
After a switch from Pycnodontiform dominance to Acanthomorph dominance
What replaced the Pycnodontiforms? Which phase is this new group associated with in terms of reef fish evolution?
The Acanthomorphs - teleost, spiny rayed fish (similar to the fish seen today).
These are found in Phase 3.
Why did the Acanthomorphs outcompete the Pycnodontiforms?
- Prioritised movement/maneuverability over armour, with a switch from heavy, interlocking ganoid scales, to light, flexible leptoid scales
- Developed pharyngeal jaws
What did the development of pharyngeal jaws allow for?
Functional decoupling.
The oral mouth is no longer required for chewing, as this can now be carried out by the second set of jaws in their throat (aka the phayngognathy). This allowed rapid evolution of the oral jaws and teeth, allowing modern features to start becoming visible.
Summarise Phase 4 of reef fish evolution.
This provided the foundations for modern coral reefs, with good interaction between the fish and corals -> important families emerged but diversity was still slightly limiting.
Where used to be the equivalent of the IAA now in terms of biodiversity? Which modern fishes and corals is there evidence of?
Monte Bolca -> found in central Europe 50 mya around the Tethys Sea.
Rabbitfishes, surgeonfishes and cardinal fishes (herbivores, nocturnal carnivores etc.) were all identified. Acropora and forms including branching, digitate, corymbose and tabulate corals were all present.
Summarise Phase 5 of reef fish evolution.
Modern reefs emerge -> global patterns match now, with biodiversity shifting to the IAA, with high turnover and fast-growth ecosystems allowing fine-scale functions to emerge.
Fine grazing and scraping developed, allowing the reef-flat to be developed via the clearing of large regions of algae (supporting coral development).
Summarise Phase 6 of reef fish evolution.
Most species emerged 5 mya, with most species emerging here.
Limited new functions emerged from phase 5 to 6, but diversity continued -> essentially rapid diversification with limited new functions.
How was the diversity of coral and reef fish taxa found to be linked? How did this change over time?
When comparing fish genera and coral genera over time, it was clear that they are closely coupled, depending on each other.
Before phase 5 = corals diversified slightly faster than fishes
Phase 5 = fishes diversified faster (e.g., fine-scale grazing techniques)
After this = corals diversified faster again (likely due to the creation of reef flats, for example, produced by the reef fishes)
