PhD exit seminar - 2011
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An overview of my PhD thesis. This presentation was given as part of my PhD completion at JCU in 2011
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PhD exit seminar - 2011
- 1. DATING THE ORIGINS OF CORAL REEF FISHES ARC Centre of Excellence Coral Reef Studies Supervisors: DR Bellwood L van Herwerden Peter F Cowman
- 2. BACKGROUND: MARINE BIODIVERSITY HOTSPOT •The Indo-Australia Archipelago (IAA) •>500 spp corals; > 5,000 spp fish •Gradient of declining richness •Patterns of biodiversity •Studies of maintenance •Less emphasis on origin and evolution of taxa
- 3. BACKGROUND: THE HOPPING HOTSPOT Renema et al. 2008
- 4. THESIS QUESTIONS 1. What are the temporal origins of trophic modes on coral reefs? 2. What roles have coral reefs played through time? 3. How has historical biogeography shaped coral reef diversity?
- 5. MATERIALS & METHODS Alignment/Supermatrix construction Model testing, partitioning AB C D MY Age estimation MCMC Bayes I BEAST Package Fossil Data (+ biogeographic) A B C D Phylogenetic reconstruction MP, ML, BI. Bootstrapping etc. Garli MrBayes Labridae (wrasses) DNA for reef fish families GenBank Max taxa, gene regions (Mt, Nuc)
- 6. AB C D MY AB C D MY AB C D MY AB C D MY MATERIALS & METHODS Labridae (wrasses) Chaetodontidae (butterflyfish) Pomacentridae (damselfish) A B C D A B C D Apogonidae (cardinalfish) A B C D A B C D Temporal Framework LTT MY
- 7. CHAPTER 1&2: TROPHIC EVOLUTION Q1: What are the temporal origins of trophic modes on coral reefs? Labridae • 600 spp, 80 genera • Diverse specialized feeding modes • Moderate fossil record • Little info on origins of novel feeding modes Chaetodontidae • 130 spp, 10 genera • 63% of all corallivores • Little info on origins of corallivory • Effect of coral feeding of speciation
- 8. Chapter 1&2: QUESTIONS & AIMS I. Patterns of trophic evolution? (wrasses) II. Origins of corallivory? Effect? (butterflyfishes) a) Trophic chronology, explore patterns (wrasses, butterflyfishes) b) Corallivory and significant cladogenesis (butterflyfishes)
- 9. CHAPTER 1&2: TROPHIC EVOLUTION Labridae Chaetodontidae hard coral feeder soft c oral feeder General Invert Gastropod Fish Plankton Herbivore Cleaner Forams Excavator Browsing Scrapers Coral Mucus Julidines Scarines Cheilines Labrines Hypsigenyines Labrichth. Cr Palae Eocene Oligo. Miocene Pl 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0
- 10. CHAPTER 1&2: TROPHIC EVOLUTION Chaetodon Corallivory Cleaner Foraminifera Plankton Coral mucus Piscivory Large gastropods Small invertebrates Palaeo. Eocene Oligo. Miocene Pli Plt/Recent 7.5 million years?
- 11. CHAPTER 1&2: TROPHIC EVOLUTION Chaetodontidae Significantly more diverse than expected Crown Chaetodon Clade C1+C2+C3+C4 Clade C2+C3+C4 Clade C3+C4 Clade C2 Clade C4 Clade C3, not significantly more diverse But contains most corallivores Move onto coral reefs underpins cladogenesis in Chaetodon
- 12. Labridae • Multiple origins • Escalation of novelty • Miocene NB • ~7.5 MY in place Chaetodontidae • Multiple independent origins (5) • Miocene NB • Significantly diverse Chaetodon • Move onto coral reefs underpinned diversification CONCLUSIONS Cleaner Foraminifera Plankton Coral mucus Piscivory Large gastropods Small invertebrates Palaeo. Eocene Oligo. Miocene Pli Plt/Recent
- 13. CHAPTER 3: CORAL REEFS AS DRIVERS OF CLADOGENESIS Q2: What roles have coral reefs played through time? Labridae (wrasses) Chaetodontidae (butterflyfish) Pomacentridae (damselfish) Apogonidae (cardinalfish) (More data) (More data) (First time) (First time) A B C D MY A B C D MY A B C D MY A B C D MY LTT Tempo Moments estimator Significantly more diverse
- 14. Chapter 3: QUESTIONS & AIMS I. Temporal concordance in reef fish origins? II. Does reef use increase diversification? a) ID congruent periods of elevated diversification b) % Reef vs Rate of Diversification (reefs as drivers) % Reef vs Extinction (reefs as refuge)
- 15. 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 Paleo. Eocene Cr. Oligo. Miocene Pl. ORIGIN AND TEMPO Expanding reefs K/T boundary
- 16. ORIGIN AND TEMPO Log # Lineages 200 100 50 20 10 5 2 1 Cr Paleo. Eocene Oligo. Miocene Pl. 70 60 50 40 30 20 10 0 Time before present (MY)
- 17. LINEAGE THROUGH TIME Fossil Phylogeny Lineages Fossil diversity Time before present (MY) (Crisp & Cook 2009) ‘hopping hotspot’ (Renema et al 2008)
- 18. CRYPTIC EXTINCTION? Log # Lineages 200 100 50 20 10 5 2 1 Cr Paleo. Eocene Oligo. Miocene Pl. 70 60 50 40 30 20 10 0 Time before present (MY) Fossil Hopping hotspot Phylogeny
- 20. SIGNIFICANT EXPANSION Pomacentridae Labridae Apogonidae Chaetodontidae Significantly more diverse lineage Alfaro et al. (2007) Bellwood et al. (2004) Williams and Duda (2008) Cr Paleo. Eocene Oligo. Miocene Pl. 70 60 50 40 30 20 10 0 Time before present (MY)
- 21. ROLE OF CORAL REEFS
- 22. ROLE OF CORAL REEFS Significant relationship between % reef occupancy (of a family) and the global rate of diversification (of a family) CORAL REEFS ACT AS A DRIVER OF CLADOGENESIS
- 23. Ability of lineages to maintain high diversification rate even with high simulated extinction ROLE OF CORAL REEFS Higher % reef High resilience against extinction CORAL REEFS ACT AS A REFUGE
- 24. CONCLUSIONS • Congruent patterns • Cryptic extinction event • Expanding coral reef habitat Supporting high diversification Refuge from high extinction Log # Lineages 200 100 50 20 10 5 2 1 Cr Paleo. Eocene Oligo. Miocene Pl. 70 60 50 40 30 20 10 0 Time before present (MY)
- 25. CHAPTER 4: HISTORIC BIOGEOGRAPHY OF FISHES ON CORAL REEFS Q3: How have historical biogeographic patterns resulted in current coral reef diversity? Labridae (wrasses) Pomacentridae (damselfish) Chaetodontidae (butterflyfish) Global Dist. Widespread Indo-Pacific Endemics EPB ? ? Barriers divide marine realms ? ? IOP 3.1 MY TTE ~12 MY
- 26. METHODS: ANCESTRAL RANGE RECONSTRUCTION LAGRANGE (REE AND SMITH 2008) 5 biogeography regions 1. East Pacific (EP) 2. Atlantic (Atl.) 3. Indian Ocean (In) 4. Indo-Australian Archipelago (IAA) 5. Central Pacific (CP)
- 27. METHODS: ANCESTRAL RANGE RECONSTRUCTION Bannerfishes (Chaetodontidae)
- 28. ORIGINATION & DISPERSAL Extant Lineages EP Atl. In IAA CP
- 29. ORIGINATION & BIODIVERSITY Regional origination/Regional Richness Tukey-Kramer Post-hoc: EP, Atl, IAA Higher In, CP Lower
- 30. ORIGINATION AND BIODIVERSITY Regional origination/Family Richness Tukey-Kramer Post-hoc: IAA Higher EP, Atl., In, CP Lower
- 31. ORIGINATION AND DISPERSAL THROUGH TIME: ANCESTRAL LINEAGES Paleo-Eocene (65-33) Global pamixia Accumulated ranges in IAA Oligocene (33-23) Regional Vicariance Restricted dispersal Survival in IAA Miocene (23-5 MY) Leap in IAA Origination Some Dispersal Pliocene-Recent (5-0 MY) Some origination Increasing dispersal Accumulation Survival Origination Expansion
- 32. BARRIERS & VICARIANCE East Pacific Barrier (EPB) •Periodically breached •West-East •Multiple causes Isthmus of Panama (IOP) •Wide distribution (~10MY) •More near final closure Terminal Tethyan Event (TTE) •No temporal congruence •Pre-TTE (Paratethys?) •Post-TTE (around Africa) Hard Barriers not that hard
- 33. BARRIERS & VICARIANCE Indian Ocean/IAA (In/IAA) •Temporal Concordance (2.5-5MY) •Bidirection dispersal •Barrier/Barriers? IAA/Central Pacific (IAA/CP) •Temporal concordance (~6MY) •Unidirection dispersal, IAA to CP •Vicariance both side of IAA •Global event? Soft Barriers have more influence? Changing Ocean Currents?
- 34. CONCLUSIONS Patterns of Origination and dispersal East Pacific & Atlantic Isolated and Independent IAA Accumulation, Survival, Origin, Expansion Indian Ocean & Central Pacific Recipient/evolutionary sink Vicariance and Barriers Hard barriers are temporally diffuse Soft barriers are temporally concordant
- 35. THESIS CONCLUSIONS Trophic Evolution: • Miocene Important for novel feeding modes Role of Coral Reef: • Drivers of claodogenesis (Miocene) • Refuge during high extinction Biogeography & coral reef diversity • IAA – Centre of Accumulation, Survival, Origin & Expansion Cleaner Foraminifera Plankton Coral mucus Piscivory Large gastropods Small invertebrates Palaeo. Eocene Oligo. Miocene Pli Plt/Recent Fossil Phylogeny
- 36. PUBLICATIONS Cowman, P.F., D. R. Bellwood, and L. van Herwerden. 2009. Dating the evolutionary origins of wrasse lineages and the rise of trophic novelty on coral reefs. Molecular Phylogenetics & Evolution. 52:621-631. Bellwood, D. R., S. Klanten, P. F. Cowman, M. S. Pratchett, N. Konow, and L. van Herwerden. 2010. Evolutionary history of the butterflyfishes (f: Chaetodontidae) and the rise of coral feeding fishes. Journal of Evolutionary Biology. 23:335-349. Cowman, P. F., D. R. Bellwood. In press. Coral reefs as drivers of cladogenesis: expanding coral reefs, cryptic extinction events and the development of biodiversity hotspots. Journal of Evolutionary Biology. Cowman, P. F., D. R. Bellwood. In prep. Historical biogeography of teleosts on coral reefs: patterns of origination and dispersal. Journal of Biogeography Cowman, P. F., D. R. Bellwood. In prep. Vicariance of teleosts lineages on coral reefs: nature of historical hard and soft barriers to dispersal. Journal of Global Ecology and Biogeography ARC Centre of Excellence Coral Reef Studies
- 37. ACKNOWLEDGMENTS • Prof. DR Bellwood, Dr. L van Herwerden • ARC Centre of Excellence, International Student Centre, G.R.S. • Colleagues: A. Hoey, S. Wismer, R. Bonaldo, C. LeFerve, S. Klanten, C. Goatley, J. Tanner. • Photos: R. Bonaldo, C. LeFevre , A. Hoey, J. Krajewski • HPC support staff, Tech support, BEAST user group members • Staff and students at Bodega Bay Applied Phylogenetics workshop • Professors, staff and students from School of Marine and Tropical Biology • Family & friends FINANCIAL SUPPORT: • Tuition fees – Endeavour International Postgraduate Research Scholarship • Stipend – JCU scholarship • Project funding – ARC Centre of Excellence (DRB), JCU Internal Research Award, Graduate Research Scheme • Conference travel – ARC Centre of Excellence, Australian Coral Reef Society, ANNiMS. • Virginal Chadwick Award for publication ARC Centre of Excellence Coral Reef Studies
- 38. QUESTIONS?
Hinweis der Redaktion
- The title of my PhD Project is : Dating the Evolutionary Origins of Coral reef fishes
- The IAA largest Marine Biodiversity Hotspot Over 500 species of corals and 5,000 species of fish associated with reef habitat in the region. Species richness declines Description of patterns of diversity surrounding the hotspot, these studies have concentrated on processes of maintenance There has been less emphasis on the origins and evolution of taxa that form the IAA hotspot
- Movement of the hotspot from an ancestral position in the Tethys, to its current location in the IAA The hopping hotspot West-East movement of fossil taxa of reefs. Details still lacking Coral reef fish poor fossil record. Molecules and age estimation technique can now fill the gaps in the fossil record A temporal framework will allow us to examine how coral reef fish evolution have been shape by past climatic and tectonic events.
- For coral reef fishes, this thesis aims to answer the following three questions: What are the temporal origins of trophic modes on coral reefs? What roles have coral reefs played in the evolution of assoicated fishes through time? How has historical biogeography shape coral reef diversity?
- Sequence data from GenBank and collaborators . Largest number of taxa and multiple gene regions. aligned into gene datasets and combined into a supermatrix Initial phylogenetic analyses were performed with Maximum Parsimony, Likelihood and Bayesian inference Age estimation Bayesian inference in the BEAST package incorporating fossil and biogeography data for tree calibration
- This was done for each of the four families to reconstruct a temporal framework. Within this framework further bioinformatics methods were used to explore the origins of trophic modes and diversification through time.
- In chapter one, the origins of trophic novelty for the labridae were explore. Family Labridae 600 species in 80 genera. Diverse and abundant Within the family there are several specialized feeding modes. Modest fossil record for the Labridae from the Eocene, there is little information on subsequence diversification and origins of novel feeding modes. The Chaetodontidae 130 species within 10 genera Corallivory 63% of all known teleost fishes that feed directly on corals However, there is little known about the origins of corallivory in the family and if access to this novel food source has allow the to rapidly diversify.
- To explore pattern of trophic evolution in the labridae and origins of corallivory in the Chaetodontidae A trophic chronology was constructed for each family, optimizing trophic character data onto a chronogram. To assess the effect corallivory had on the evolution of chaetodontid lineage a metric was used to identify lineages that were significanlty more diverse than expected give the rate of diversification for the entire family.
- The trophic chronology of the Labridae identifies ancestral origin of eleven distinct feeding modes which are colour coded here Representative species are also shown for each feeding mode. Origins at k/T. Eocene most major lineages are in place. The origins of trophic mode display multiple origins with no temporal concordance i.e. trophic modes do not arise at the same time. ##### The Chaetodontidae appear much younger than the Labridae with crown origins in the Oligocene at 33 Million years. Corallivory has arisen multiple times in three of the four major lineages of the genus Chaetodon with two type: hard coral feeders, and soft coral feeders.
- There is a pattern of escalating trophic diversity from the Paleocene, with the Miocene being important for the evolution of extremely novel feeding modes in wrasses, and the origins and escalation of corallivory in butterflyfishes ##### However for the last 7.5 Million years there has been no new trophic modes arising in the Labridae. By the late Miocene, for the labridae, the trophic system appears to have been in place. There is still diversification of new lineages in the Pliocene for both families, but these lineages to not display a new feed more.
- Patterns of significant cladogenesis in the Chaetodontidae reveal several crown lineages with signifcantly higher extant species richness then you would expect given its age and the overall rate of diversification for the family. ##### However Chaetodon clade 3, which contains the highest number of corallivores, was not found to be signifcanlty more diverse. ##### Optimisation of habitat preference places a move onto coral reefs at the stem of the Chaetodon lineages which shows significant diversity. It appears the signficant diversification within Chaetodon is underpinned by a move to coral reef habitat. While a switch to coral feeding gave some lineages access to a novel and abundant feeding source it is the actually association with the habitat that has allowed them to diversify.
- To Conclude these chapters: Within the labridae I have identified multiple origins of trophic feeding modes with no temporal concordance However ther is two distinct pulses with innovation in the Miocene important for extremely specialized feeding modes. And the trophic system for labrids on reefs has been in place for the last 7.5 Million years. #### In the Chaetodontidae, there has been 5 independent origins of corallivory, all within the genus Chaetodon. Again the Miocene is important for the origin and escalation of corallivory. While Chaetodon displays signifcant diversity, it cannot be directly linked to a switch to corallivory. A move to coral reef habitat foreshadows diversification in Chaetodon. The role of coral reefs in underpining extensive diversification warrents further investigate to identify if this is a general phenomenon for reef associated fishes.
- Re examine the Labridae and Chaetodontidae with more data. Pomacentridae and Apogonidae, for the first time. Temporal framework several diversification statistics are used to explore and quantify changing diversity through time. Specifically I examine Lineage through time plots to identify the changing tempo of speciation I use a method of moments estimator to identify significantly diverse lineages. This metric compares the net rate of speciation to the of a lineage to that of family to see if it has resulted in sigificantly higher species richness This is done at increasing increment of simulated extinction to identify which lineages can remain significantly diverse at high despite high extinction
- By exploring LTT plots i was able to identify patterns in reef fish origins & periods of elevated cladogenesis. I compared the % coral reef association of Families to their global diversification rate. Specifically do coral reefs drive cladeogenesis? I also compared the % reef association of significantly diverse lineages with their ability to remain significantly diverse at high simulated extinction rate. i.e. Do reefs act as a refuge from high extinction rates.
- Four families show remarkable congruence The Labridae shown here, along with the Apogonidae and Pomacentridae show establishment of initial major lineages following the K/T boundary impact. Extensive diversification during the Oligocene/Miocene epochs, a time period that is linked to the rapid expansion of coral reef habitat in the IAA.
- A lineage through time plot shows the accumulation of lineages from a chronogram over time On the y axis is the number of lineages on a log scale, and the x axis is time before present. The shape of a lineage through time plot can show changing rates of diverisifcation over time. For the Labridae, Pomacentridae,and Apogonidae the Paleocene and Eocene portion of the LTT plot is curved, followed by a more linear progression in the Oligocene and Miocene. An inflection in the Oligocene is synchronous with the origins of major lineages in the Chaetodontidae that later seem to experience rate increase.
- The utility of an LTT plot is that the contribution of speciation and extinction may be seen in the absence of a fossil record. There are several patterns that can describe different evolutionary processes If we examine the accumulation of fossil lineages in the fossil record before and after an extinction event, we would see a decline in fossil taxa at the extinction event, with a subsequent increase of new fossil lineage. The same event would translation to a molecular phylogeny of extant species as a curve followed by an inflection just after the extinction event. The increasing LTT curve after hte event is associated with the expansion of surviving lineages This pattern is remarkable similar to that of the Labridae and the Pomacentridae and the timing of an inferred cryptic extinction event is synchronous with the hopping hotspot
- Going back to the LTT plot, If we look at fossil diversity of marine organism, we see a drop rapid drop in diversity at the K/T boundary and again at the Eocene/Oligocene boundary. While relatively prolonged, this period of fossil decline may point to increaesd extinction of marine fauna at that time. At least for these reef fishes, the reduction of habitat in the ancestral Tethian/Arbian hotspot at this time may have resulted in extinction of some lineages, while the establishment of the IAA hotspot allowed surviving lineages to flourish. However we still do not know if all surviving lineages reacted in the same way. Do lineages associated with this rate increase show significant species richness?
- Using several diversification statistics, I identify lineages with significantly more diversity than expected give the age of the lineage and its extant diversity. Red triangle show lineages with significantly higher diversities than expected at high levels of extinction (50 up to 90% extinction), yellow is low extinction (0-50%)
- Overlaying the ages of these significant lineages onto the LTT identifies the Miocene, and to a lesser extent the Oligocene, as an epoch that has produced the most diverse lineages. No lineage is older than ~33 million years, the timing of a possible cryptic extinction event. This pattern holds true for other fish groups, and gastropods: Turbo, Echinolitterina and Conus The taxa that represent these diverse lineages all appear to have a close relation ship with coral reefs
- In fact every lineage that was found to be significantly more diverse at high simulated extinction rates (red triangle) has over 50% of its member taxa associated with coral reefs. Each star on the tree here identifies a significantly diverse lineage, that has over 50% of its member taxa associated with coral reefs.
- For the four families and data re-examined for the Tetraodontiform families, there is a significantly relationship between the rate of diversification and % of coral reef associated taxa. In this way coral reefs appear to act as drivers of cladogenesis.
- There is also a relationship between the simulated extinction level at which the diverse lineages in each family remained significantly diverse, and % coral reef association This highlights the ability of coral reef assoicated lineages to maintain high diversification rates, even at high simulated extinction. When times have been tough and extinction has been high, coral reefs have had the potential to act as a refuge for associated lineages allowing them to diversify more than there non reef counterparts.
- In summary, this chapter identifies congruent patterns in the origins of four coral reef fish families Decreasing or low rates of diversification in the Paleocene/Eocene with a subsequent upturn the Oligocene point to a loss of lineages through cryptic extinction, which may have links to the demise of an ancestral Tethys hotspot. Significant cladogenesis in the Miocene is driven by surviving lineages associated with coral reefs, which expanded in the IAA during that period Coral reef habitat supports high diversification of associated lineages, And has a potential role as a refuge in times of high extinction.
- In chapter four I examine patterns of historic biogeography of the Labridae, Pomacentridae and Chaetodontidae. These three families are globally distributed both on and off reefs in the tropics, and contain both widespread indo-pacific ranges, and endemics. Lack of physical barriers and long distance dispersal of pelagic larva can blur biogeographic patterns over time There are 2 known hard barriers which have split the marine tropics into the Indo-Pacific and the Atlantic. The Terminal Tethyan event and more recently the Isthmus of Panama. There are also several soft barriers that may have caused vicariance in lineages at different times, particularly in the the Indo-Pacific, the most notable being the East Pacific Barrier. However, we do not known the timing and extent these barrier have influenced the evolution of reef fish lineages in different biogeographic regions.
- Ancestral range reconstruction was performed in the program Lagrange with presences/absence data for extant taxa in 5 distinct biogeography regions The East Pacific, The Atlantic, Indian Ocean, the IAA and the Central Pacific. Within the analyses I included information reflecting the biogeographic barriers and reduced dispersal potential between adjacent regions. Results allowed me to quantify regional lineage richness, origination, dispersal, and vicariance among regions for the three families through time.
- This is an example of the results from a Lagrange ancestral range reconstruction This is the bannerfish lineage within the Chaetodontidae. At each node the most optimal range inheritance scenario is reported. At each node speciation can result in sympatric inheritance # vicaricance, or peripheral isolation, among the 5 marine regions #### Along branches dispersal, and local extinction are also inferred
- This figure show the regional richness, regional origination, and dispersal to adjacent regions for all three families for currently extant lineages (ie the tips of the tree) Firstly the IAA stands out as the biodiversity hotspot, of which most of the lineages present there, arose in the region. The IAA also exports a large proportion of lineages to adjacent regions in the Indian Ocean and Central Pacific, were within region origination is low. Both the East Pacific and Atlantic regions have lower regional richness, but have high regional origination. There is also little dispersal from the Indo-Pacific regions to the Atlantic and East Pacific.
- Examining the proportion of regional origination that account for regional richness identifies the EP, Atl and IAA and having high regional origination. Most of the extant lineages in those regions today, arose within those regions.
- If we look at proportion of regional origination that accounts for the global family diversity only the IAA stands out as significantly higher than the other region. For the three family, about 60% of their diversity arose within the IAA.
- As with the tips of the trees, origination and dispersal can be quantified through time. This was done for all three families, but I present data for the Labridae. For the labridae, the Paleo-Eocene reflect panmixia between regions with widespread lineages and restricted lineages accumulate in the IAA. During the Oligocene widespread ranges begin to break down with vicariance between regions and restricted dispersal. The centre of paleodiversity for molecular lineages is in the IAA. If we take into account extinction that is highlighted in other regions and its confounding effect on molecular phylogenies the IAA in the Oligocene appear to be a centre of ancestral lineage survival. The Miocene is characterized by extensive origination in the IAA, with some dipersal out out of the hotspot. The Pliocene to Recent sees some origination within regions, but a huge expansion of lineages from the IAA to adjacent regions. This highlights the changing role of the IAA in the evolution of reef fish biodiversity The IAA has sequentially, and simultaneously act as a centre for lineage Accumulation, Survival, Origin and expansion Several authors have argued over which of these roles the IAA has play. But infact it has been all of them at different times.
- This graphic displays vicariance events inferred from the analyses and there association with know historical barriers. Vicariance associated with the East Pacific barrier happened on several occasions, following isolated dispersal events. Dispersal has only occurred from West. The lack of temporal concordance shows that multiple causes could have resulted in vicariance across this barrier. The Isthmus of Panama shows a wide distribution of events from the final close of the barrier at 3.1 MY back to at least 10 MY. There are more event closest to the closure. For the TTE, there is no temporal congruence between families, nor do event seem to be temporal restricted to the timing of the TTE (18-12 MY) Older event may be related to the formation of the Para-tethys, an enclosed ocean basin. And younger event occurred following dispersal around the horn of Africa. Overall the hard barriers are not as hard as previously thought with a diffuse pattern reflecting early restriction of gene flow and alternative dispersal routes.
- Vicariance events between the Indian ocean and the IAA show a temporal congruence among families with a concentration of event between 2.5 and 5 MY year ago. Post-Speciation dispersal occurs in both directions across the barrier. On the other side, vicariance between the IAA and Central Pacific is also temporally congruent among families with most event occuring at 6 MY. Post speciation dispersal across the barrier is Unidirectional from the IAA to the central Pacific The temporal congruence in vicariance either side of the IAA is remarkable give the complex geographic and occurrence of widespread lineages. The timing of events is too old for Pleistocene Sea-level change and the post-speciation dispersal ability of lineages highlights the temporary nature of these potential barriers. Vicariance on both sides of the IAA could be linked to changing ocean currents, however more study is need to find the true cause.
- To summarise this chapter, East Pacific and Atlantic Biota have been largely isolated and Independent from other regions At different points into the IAA has been a centre for lineage accumulation, Survival, origination and expansion. The Indian Ocean and Central Pacific have largely acted as recipient, or a evolutionary sink for expanding lineages from the IAA Vicariance across hard barriers are temporally diffuse, while soft barriers show temporal congruence and concordance.
- Finally to summerised the main conclusions of this thesis For trophic evolution, the Miocene is an important time for novel feeding modes. Coral reefs have a role of driving diversification of associated lineages particularly in the Miocene. And also provide a potential refuge from extinction. For biogeography, the IAA has been a major source of global diversity, and temporal has head several roles as a centre for lineage accumulation, survival, origin and expansion.