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Annotated Bibliography
Allison Guggenheimer TA: Matthew Holding Evolution Rec Tuesdays 8:00 AM 15 September 2014 Climatic Evolution of Corals

Culver S., & Rawson P. (2000). Biotic response to global change: the last 145 million years. New York: Cambridge University Press.

Culver and Rawson include climatic evolution information from several major countries and oceans in their book. It covers particularly modern climatic events choosing to focus on more recent and future global changes. It looks particularly upon global warming. This keeps the information focused and not overwhelming.

The book discusses flora, fauna, geography, oceanic circulation and sea levels, and much more. It covers one taxonomic group at a time breaking down the changes each has experienced. Chapter twelve is particularly useful as it looks into how coral reefs have suffered and come back as well as how they are symbiotic with algal populations. It would be directly related to climatic evolution of corals and would give broad details about the subject.

Parmesan C. (August 24, 2006). Ecological and Evolutionary Responses to Recent Climate Change. Austin: Annual Reviews.

Parmesan collected information on a wide variety of climatic evolution shifts based on global warming. She looks into flora and fauna in aquatic and terrestrial environments. She gathered her information from research done in the field, on organisms’ physiology, and in the laboratory. She shows that organisms that are range-restricted suffer the most form global climate warming. Details include food source and resource use evolving in these affected species. Parmesan has written about both genetic shifts and the minimal effects these have on the species’ survival.

A particularly useful section is that on coral reefs in the tropics. This section explores algal symbiosis, temperature changes, chemical changes, shifts in allelic frequency, and more. This is exactly the kind of details necessary for the topic of climatic evolution of corals. It gives a logical break down of how physical evidence is complied to show evolution in a species.

Hoegh-Guldberg O. (1999). Climate change, coral bleaching and the future of the world’s coral reefs. Collingwood: CSIRO Publishing.

Hoegh-Guldberg chose to focus on the oceanic temperature increases and their effects on coral. In particular he looks into coral bleaching. This is when the zooxanthellae that live on coral and the coral itself die due to an inability to cope wit their environment. In this case the symbiotic relationship is destroyed by increasing ocean temperatures that are unsuitable to the pair. There has been a major loss in coral world wide due to this phenomenon. Coral bleaching is broken down into ecological, chemical, and organism structure effects. Using past data the future of the reefs is projected. The author tests if the coral will be able to keep up evolutionarily and suspects it will not, though there is some change occurring.

Though it is not very optimistic, the perspective on coral evolution due to climatic change is a very unique one. It talks specifically about coral bleaching, which helps with the details of exactly what is happening to the organism’s body due to the climate. It also shows how the evolution may not be able to keep up with the changes in order for the coral to survive. It would add a distinct viewpoint on the disadvantages of slow evolutionary processes.

Phinney J., American Geophysical Union, et al. (2006). Coral reefs and climate change: science and management. Washingon DC: American Geophysical Union.

The authors talk specifically about the many changes coral reefs are undergoing due to climate change. This focused approach addresses issues of aquatic temperatures, coral history, disease, coral bleaching, population response, reef management, etc. This is sort of manual that informs readers of the problems coral faces due to climatic changes, how it has changed over the years, and ways to assist with the problems caused. Phinney and colleagues would give a nice array of data and multiple problems climate change has caused in coral as well as how it is adapting to this change. This would be an excellent way to find out how evolution is being stimulated and tampered with.

Baker A. (12 August 2004). Coral reefs: corals’ adaptive response to climate change. London: Macmillan Journals ltd. Baker discusses that although many believe that there is no response of coral to the dramatic climatic changes in recent times, there is evidence that a particular symbiotic relationship with an odd algae species enables coral to withstand rising oceanic temperatures. There has been a larger number of these coral algae pairs found in areas with high climate change damage. Baker gives hope that this shift in frequency could help coral resist extinction due to climate at least for some time. Baker has found a prime example of evolutionary selection for a particular coral type due to climate change. This would add a great example of how more than one organism can work together to survive changing climates. It would give depth to the idea that climate change can be adapted to in several ways.

Wikipedia Talks & Edits
-Web address: https://en.wikipedia.org/wiki/Coral

-Improvements:

1. The coral article could really improve from having more content added to the evolutionary history section. This simply has few small paragraphs that briefly run through the fossil record of coral. Some things that could be added are images of fossils and causations for their adaptation and evolution.

2. The gallery of photos at the bottom of the page is very sparse. There are only eight actual photographs of coral. There are many species and beautiful varieties of coral, and they are not properly represented by this minute selection of images.

3. The section on perforate corals is brief and confusing. It is only three sentences long and does not do a good job describing the hard solid skeletons in the imperforate corals and how that causes them to differ from perforate corals.

-Edit: Climate research

Increasing sea temperatures in tropical regions (~1 degree C) the last century have caused major coral bleaching, death, and therefore shrinking coral populations since although they are able to adapt and acclimate, it is uncertain if this evolutionary process will happen quickly enough to prevent major reduction of their numbers.

-Citation:

Hoegh-Guldberg O. (1999). Climate change, coral bleaching and the future of the world’s coral reefs. Marine and Freshwater Research. 50:839-99.

Final Wiki Page Edits
-Web address: https://en.wikipedia.org/wiki/Coral#Climate_research

-Please note: all of the edits can be found under the Climate Research section and have their citations linked on that page.

Though coral have big populations and phenomenal sexual capabilities as well as zooxanthellae being diverse, evolution is sometimes slowed by abundant asexual reproduction. It seems as though the gene pool is certainly diverse, but the slow adaptation could be due to a lack of alleles mixing through sexual reproduction. Also, gene flow is variable among coral species. According to biogeography of coral species gene flow cannot be counted on as a dependable source of adaptation as they are very stationary organisms. Also, coral longevity might factor into their adaptivity. Their long life span yields fewer generations per year and therefore mutation rates are lower than shorter generation organisms. This does not allow for much selection, adaptation, and successful evolution of a species.

However, evidence of coral adaptation to climate changes has been shown in many cases. These are usually due to a shift in coral and zooxanthellae genotypes as is typical of evolution when selection factors change. These shifts in allelic frequencies have already been progressing toward more tolerant types of zooxanthellae. Scientists found that a certain scleractinain colonies of zooxanthellae are becoming more common in areas of high sea temperatures. It may cause a bottleneck in the endosybiant gene pool, however this genotype may rescue the coral populations from complete decimation in the coming years. Though there may be this adaption to more tolerant zooxanthellae, there will be costs in communal layout and output. Meaning the lowered variety in alleles and change in selection pressures may cause other physiological cost to the organisms. These more favorable symbionts seem to have slower photosynthesis rates. This trade off indicates an evolutionary shift of what traits are most selected for in the current environment in terms of survival.

Another coral evolutionary response are refugia population shifts as a reaction to temperature pressures. In the Gulf of Mexico, where sea temperatures are indeed rising, there has been a migration of cold-sensitive staghorn and elk horn coral. Not only have the symbionts and specific species been shown to shift, there seems to be a certain growth rate favorable to selection. It has been found that slower growing coral have become more common as they are more heat tolerant. However, the changes in temperature and acclimation are complex. Some reefs in current shadows represent a refugium location that will help them adjust to the disparity in the environment even if eventually the temperatures may be rising more quickly there than other locations. This vicariance due to climatic barriers causes a realized niche to shrink greatly in comparison to the old fundamental niche. Scientists have found direct evidence of selection acting upon this coral life system by exploring different angles of adaptation, but conclusions are difficult to draw.

Final Draft
Rising Ocean Temperatures and Coral Bleaching Lead to Climatic Evolution

Many organisms have survived throughout the history of earth though experiencing severe conditions. The phylogenetic tree takes quite a trimming at times, as not all species make the cut. Environments have fluctuated from tropical swamps to ice age glaciers testing their physical adaptations and biochemical ability to cope and adapt. There are many organisms that demonstrate climatic evolution, which forms a major subdivision of all evolution. One organism that exceptionally demonstrates this is coral. Out of many ecosystems coral reefs seem to be one of the most susceptible to upcoming climatic shifts (Donner et al. 2005). In the coming years coral should show disturbance on a worldwide and local level according to evolutionary patterns of their ancient past (Hughes et al. 2003). It is debated if these disturbances will cause timely sympatric speciation or lead to the extinction of coral. Either way, there are definite changes in coral populations presently and this indicates evolutionary forces at work.

A majority of coral climatic evolution studies focus on coral bleaching. Zooxanthellae live in symbiosis with coral but when water temperatures become higher than their tolerance level the coral become bleached (Hoegh-Guldberg 1999). The bleaching itself is due to the expulsion of these microalgal organisms (Hughes et al. 2003). The name coral bleaching refers to white or light appearance of coral from their loss of color that usually comes from these zooxanthellae (Hughes et al. 2003). For example, beached coral often has this pale appearance as it has lost its living symbionts. Although it might be hard to fathom the amount of damage these climate changes cause, many scientists have studied and found the extent of damage to be extensive already and suggest coral populations will continue to plummet. To illustrate, the biomass of coral fell by 80.9% when water temperatures were set to a reasonable speculative increase in a model situation (Alva-Basurto and Arias-Gonzalez 2014). These dramatic changes represent a problem for coral survival and can be explained by rising global temperatures, temperature sensitivity of coral, and a lack of quick adaptation.

In the past several years there has been an evident increase in temperatures globally. In the last century the temperature of oceans has gained about one degree Celsius in tropical areas and is predicted to continue and perhaps accelerate to two degrees per century (Hoegh-Guldberg 1999). While one degree may not seem very dramatic to the majority of people, for those who study coral it is clear that small fluctuations in temperature can have tremendous impacts. Their ability to maintain homeostasis, especially with symbionts, is a delicate balance. The connection between rising sea temperatures and coral bleaching is further demonstrated by the correlation of coral death and intense temperature rise zones. Confined regions of high sea surface temperature coincide with current coral bleaching locations (Li and Reidenbach 2014). Li and Reidenbach show that coral bleaching is dependent on locations of climatic sea temperature increase (2014). These zones are therefore possible hot spots for extinction. Also, a great upsurge in temperature spikes caused by climate episodes such as El Niño are a concern for coral (Parmesan 2006). This other source of climatic temperature flux can contribute to the stressors coral face. The cause of this bleaching is well established and documented, but the corals’ reaction to these temperature rises is what determines its evolutionary fate.

The corals’ extreme sensitivity to the temperature changes is what makes it such an observable model of climatic evolution. Coral bleaching can occur at a simple one-degree change in temperature above a typical summer peak (Donner et al. 2005). Their inability to cope with minute temperature change seems to predict a failure of adaptation to new environments. It is hard not to think in context of Homo sapiens when it comes to temperature environments, as they are capable of adapting to a variety of climates. To explain in context of H. sapiens, that is one degree per human lifespan. In context of time, these temperatures changes are more dramatic than they may initially seem. In addition, Alva-Basurto and Arias-Gonzolez modeled an inverted connection between coral biomass and rising sea temperatures (2014). This means increasing in sea temperatures shows a negative correlation with coral livelihood. This evident association and measurable rise in temperatures indicate a harsh natural selection on coral populations. It was found that when average sea temperatures are high there is an abundance of bleaching, and when the temperatures are lower there is no bleaching though there is some variance (Sammarco et al. 2006). This continuous negative relationship of sea temperature and coral bleaching death is an accepted trend and cannot be written off to chance. Corals’ adaptation or incapability to response to this pull will determine their future speciation or extinction.

The established factors of rapidly rising ocean temperatures and coral sensitivity beg the question of the organism’s actual response. Coral have low ability to acclimate and high physiological reactivity leading to their weakness to climate changes (Alva-Basurto and Aris-Gonzolez 2014). This is an unfavorable combination for survival. The coral and their microalgal symbionts may not have the capability to evolve at a rate equivalent to oceanic temperature rises (Hughes 2003). Hughes suggest a disconnect between the demand the climate is putting on coral and its evolving abilities. Baker states that in the long run coral has not been openly shown to adapt to the rise in sea temperatures (2004). Most research seems to voice a concern for the sluggish speed that coral seems to be adapting to the global temperature increases. Aspects of adaption depend on coral itself and its zooxanthellae counterpart. Possible adaptation can occur through genetic diversity and gene flow. Though coral have big populations and phenomenal sexual capabilities as well as zooxanthellae being diverse, evolution is sometimes slowed by abundant asexual reproduction (Hughes 2003). It seems as though the gene pool is certainly diverse, but the slow adaptation could be due to a lack of alleles mixing through sexual reproduction. Also, gene flow is variable among coral species (Hughes 2003). According to biogeography of coral species gene flow cannot be counted on as a dependable source of adaptation as they are very stationary organisms. Also, coral longevity might factor into their adaptivity (Hughes 2003). Their long life span yields fewer generations per year and therefore mutation rates are lower than shorter generation organisms. This does not allow for much selection, adaptation, and successful evolution of a species.

However, evidence of coral adaptation to climate changes has been shown in many cases. These are usually due to a shift in coral and zooxanthellae genotypes as is typical of evolution when selection factors change. These shifts in allelic frequencies have already been progressing toward more tolerant types of zooxanthellae (Parmesan 2014). Baker found that a certain scleractinain colonies of zooxanthellae are becoming more common in areas of high sea temperatures (2004). It may cause a bottleneck in the endosybiant gene pool, however this genotype may rescue the coral populations from complete decimation in the coming years. Though there may be this adaption to more tolerant zooxanthellae, there will be costs in communal layout and output (Donner et al. 2005). Meaning the lowered variety in alleles and change in selection pressures may cause other physiological cost to the organisms. These more favorable symbionts seem to have slower photosynthesis rates (Donner et al. 2005). This trade off indicates an evolutionary shift of what traits are most selected for in the current environment in terms of survival.

Another coral evolutionary response are refugia population shifts as a reaction to temperature pressures. In the Gulf of Mexico, where sea temperatures are indeed rising, there has been a migration of cold-sensitive staghorn and elkhorn coral (Parmesan 2014). Not only have the symbionts and specific species been shown to shift, there seems to be a certain growth rate favorable to selection. It has been found that slower growing coral have become more common as they are more heat tolerant (Baskett et al. 2009). However, the changes in temperature and acclimation are complex. Some reefs in current shadows represent a refugium location that will help them adjust to the disparity in the environment even if eventually the temperatures may be rising more quickly there than other locations (McClanahan et al. 2007). This vicariance due to climatic barriers causes a realized niche to shrink greatly in comparison to the old fundamental niche. Scientists have found direct evidence of selection acting upon this coral life system by exploring different angles of adaptation, but conclusions are difficult to draw. It may not appear that coral have a huge impact on humans, but they are much more influential than many realize. Though there are many environmental impacts of bleaching, a major ecological concern is the suffering fish populations that make these coral their homes in addition to other species (Munday et al. 2008). The fish are affected via composition, functioning, and conduct (Munday et al. 2008). These changes can devastate the diversity of the species. A large number of fish species are effect by coral. Out of coral reef fish, 10% need coral to survive (Munday et al. 2008). Other than environmental concerns, humans depend upon coral for economic reasons especially in tropical areas (Hughes 2003). Coral reef ecosystems are home to a beneficial and diverse group of organisms and their devastation cannot help but create a ripple effect on humans. Consider that the United States reaps at least five billion dollars a year just from coral reef fishing (Munday et al. 2008). This is a significant amount of economic power and that is not even considering the effect it has on other more dependent countries. As for current coral data, their longevity as a species is ominous. Li and Reidenbach predict that by 2084 almost all coral will be at risk of death due to climatic bleaching except in very low stress areas (2014). This devastation is happening at an alarming rate. It is possibly due to immense coral death events that are likely to occur in the Caribbean soon (Li and Reidenbach 2014). There is little time for the coral to accumulate random mutations that could lead to a few beneficial allelic combinations. Presently coral are having their inadequate capabilities pushed to the maximum (Baskett et al. 2009). Right now 30% of corals are affected and by 2030 it is estimated that 60% will be (Hughes 2003). This doubling in just a few years demonstrates the rapid decline the corals are experiencing. Studies found that in the next 100 years populations of coral with and without diverse zooxanthellae will die in all three of their simulations (Baskett et al. 2009). Predictions are grim in the scientific community if climatic trends continue.

In an effort to preserve coral reefs, there are several steps scientists suggest to prevent further damage to these important ecosystems. Additional coral stressors such as disease, nutrient loading, overfishing, and sedimentation further the bleaching problem caused by climate change (Donner et al. 2005). A reduction of any of these could give the coral a better chance to adapt and cope with the temperature stressors. A clear example of an external stressor is an organism that takes over the niche dead coral provide. Seaweed has been shown to take over bleached areas of coral worsening the problem by preventing recovery (Diaz-Pulido 2009). While it may seem like protecting the coral regions could have no effect since the stressor is temperature, coral reefs can be protected by marine protected areas (MPAs) and no-take areas (NTAs) by reducing extra stresses discussed earlier (Hughes 2003). This allows better recovery of temperature dependent bleaching. Also, directing attention to alternate methods of preservation an efficient route. Studies concluded that focusing on resistant corals is an ideal preservation goal (Baskett et al. 2009). This will reduce the genetic diversity more quickly, but if they are going to die an alternative would be to preserve the strong species. In addition, a decent reduction of greenhouse gasses in the next century could prevent total annihilation of coral (Baskett et al. 2009). This cut back is a lofty goal, but it might be a worthwhile method to stop substantial coral death. The changes necessary to fight the climatic evolution of coral are monumental, however it may be the only way to prevent their complete extinction and the impact that it would cause on the world.

Works Cited

Alva-Basurto, J and Arias-Gonzalez, J. 2014. Modeling the effects of climate change on Caribbean coral reef food web. Ecol Model 289:1-14. Baker, A. 2004. Corals’ adaptive response to climate change. Nature 430:741. Baskett, M., Gaines, S., and Nisbet, R. 2009. Symbiont diversity may help coral reefs survive moderate climate change. Ecol Appl 19:3-17. Diaz-Pulido, G., McCook, L., Dove, S., Berkelman, R., Roff, G., Kline, D., Weeks, S., Evans, R., Williamson, D., and Hoegh-Guldberg, O. 2009. Doom and Bloom on a Resilient Reef: Climate Change, Algal Overgrowth and Coral Recovery. PLoS ONE 4:1-9. Donner, S., Skirving, W., Little, C., Oppenheimer, M., and Hoegh-Guldenberg, O. 2005. Global assessment of coral bleaching and required rates of adaptation under climate change. Glob Chang Biol 11:2251-65. Hoegh-Guldberg, O. 1999. Climate change, coral bleaching and the future of the world’s coral reefs. Mar Freshwater Res 50:839-66. Hughes, T., Baird, A., Bellwood, D., Card, M., Connolly, S., Folke, C., Grosberg, R., Hoegh-Guldberg, O., Jackson, J., Klepas, J., Lough, J., Marshall, P., Nystrom, M., Palumbi, S., Pandolfi, J., Rosen, B., and Roughgarden, J. 2003. Climate Chang, Human Impacts, and the Resilience of Coral Reefs. Science 301: 929-33. Li, A. and Reidenbach, M. 2014. Forecasting decadal changes in sea surface temperatures and coral bleaching within a Caribbean coral reef. Coral Reefs 33:847-61. McClanahan, T., Ateweberhan, M., Muhando, C., Maina, J., and Mohammed, M. 2007. Effects of Climate and Seawater Temperature Variation on Coral Bleaching and Morality. Ecol Monogr 77:503-25. Munday, P., Jones, G., Pratchtt, M., and Williams, A. 2008. Climate change and the future for coral reef fishes. Fish and Fisheries 9:261-85. Parmesan, C. 2006. Ecological and Evolutionary Responses to Recent Climate Change. Annu Rev Ecol Evol and Syst 37:637-69. Sammarco, P., Winter, A., and Stewart, J. 2006. Coefficient of variation of sea surface temperature (SST) as an indicator of coral bleaching. Mar Biol 149:1337-44.