Feature Paper: Porter JW (1974). Community structure of coral reefs on opposite sides of the Isthmus of Panama. Science, 186(4163):543-545.
Author Abstract: Competition for space among reef corals includes interspecific destruction by extracoelenteric digestion, rapid growth, and overtopping. No Caribbean species excels in all strategies, and on western Caribbean coral reefs there is a positive correlation between coral abundance and diversity. On eastern Pacific coral reefs, however, Pocillopora damicornis excludes other corals, and on these reefs there is an inverse relation between coral abundance and diversity, except in areas where disturbances, such as Acanthaster predation, offset space monopolization.
Note to Readers: Follow links above for author email, full article text, or the publishing scientific journal. Author notes in my review are in quotes.
Review: Before continuing with a scientific journal article review this week, I'll mention just one more point: I've completed the first brief underwater surveys for an island north of Mindanao, Philippines, but I haven't worked up the data yet, so as soon as I can finish that, I'll post the results here on Science Corner.
Okay, on with the review. The paper I've chosen this week is a classic paper and it has ramifications for another classic paper by Connell where he compared the diversity of tropical rainforests and coral reefs and found that their diversities were a result of "intermediate disturbance" on a consistent basis. However, as this week's paper shows, such a result is only likely among Pacific reefs and not among Caribbean reefs. Thus, the common theme in a lot of science is that one should be careful of extrapolating findings from one area of the world to another. Unfortunately, since the highest diversity of corals and reef fishes lies in the coral triangle (central Philippines to central Indonesia and east to the Solomon Islands and northern Papua New Guinea), a lot more coral reef research effort today tends to be given to those reefs compared to the rest of the world. Granted, there are few countries today that don't have relatively well-surveyed reefs, but my main point is that one must be careful with extrapolating their research findings.
In this week's paper, the author found that in the Caribbean surrounding Panama, "there is a positive correlation between coral abundance and diversity" while the opposite, inverse relationship is found in the eastern Pacific Panamanian coast. The author found that Caribbean scleractinian (hard, reef-building) corals are not as competitive as Pacific corals. This means that as coral numbers (abundance) increases, so too does coral diversity (# species) because there are no individual corals that are particularly aggressive to the point where they can outcompete their neighbors and create monospecific stands. In the Pacific, on the other hand, there are corals that are very competitive such that as abundance (coral numbers) increase, the chances that a few very competitive corals make up a larger proportion of the faunal community increases. As a result, coral diversity does not increase with increasing abundance.
The only exceptions to the inverse relationship in the Pacific (that the author found) were during cases of disturbance, such as after hurricanes or when Acanthaster planci (crown of thorns seastars) predated large areas of corals, paving the way for recolonization by other coral recruits.
In Pacific Panama, the coral Pocillopora damicornis was the strongest competitor on their reefs, though elsewhere in the Pacific (such as in the coral triangle), Acropora spp. tend to be the dominant competitors.
The author also found that "although the relative abundances of the coral species change markedly [in Pacific Panama following crown of thorns seastar predation events], for the most part, the order of abundance does not." Hierarchies of dominance followed levels of competitiveness among various coral species.
These results contrast with those of the Caribbean, where "except for several acroporids, which calcify relatively rapidly, no consistent relation exists between a coral's calcification rate and its prevalence on a Jamaican reef."
The reasons why such a dynamic occurs were succinctly summarized by the author: "In the eastern Pacific, rapid growth and high digestive dominance are present in the same species. In the Caribbean, the opposite is true: The species that calcify and grow most rapidly are the least capable of eating other species, while the species that grow most slowly are highest on the digestive dominance scale." As a result, in the Caribbean, high-diversity areas have lots of slow-growing corals that are able to protect their immediate surrounds from competitors through specialized "sweeper tentacles" that digest closely growing neighbors. In the Pacific, fast-growing and competitive corals outcompete slower-growing taxa to the point where areas of high-diversity tend to be lacking in highly competitive species.
Hopefully by revisiting this classic paper, some good principles can be applied to now-extensive global coral assemblage data to determine how extensive the results of this limited study apply.
Author Abstract: Competition for space among reef corals includes interspecific destruction by extracoelenteric digestion, rapid growth, and overtopping. No Caribbean species excels in all strategies, and on western Caribbean coral reefs there is a positive correlation between coral abundance and diversity. On eastern Pacific coral reefs, however, Pocillopora damicornis excludes other corals, and on these reefs there is an inverse relation between coral abundance and diversity, except in areas where disturbances, such as Acanthaster predation, offset space monopolization.
Note to Readers: Follow links above for author email, full article text, or the publishing scientific journal. Author notes in my review are in quotes.
Review: Before continuing with a scientific journal article review this week, I'll mention just one more point: I've completed the first brief underwater surveys for an island north of Mindanao, Philippines, but I haven't worked up the data yet, so as soon as I can finish that, I'll post the results here on Science Corner.
Okay, on with the review. The paper I've chosen this week is a classic paper and it has ramifications for another classic paper by Connell where he compared the diversity of tropical rainforests and coral reefs and found that their diversities were a result of "intermediate disturbance" on a consistent basis. However, as this week's paper shows, such a result is only likely among Pacific reefs and not among Caribbean reefs. Thus, the common theme in a lot of science is that one should be careful of extrapolating findings from one area of the world to another. Unfortunately, since the highest diversity of corals and reef fishes lies in the coral triangle (central Philippines to central Indonesia and east to the Solomon Islands and northern Papua New Guinea), a lot more coral reef research effort today tends to be given to those reefs compared to the rest of the world. Granted, there are few countries today that don't have relatively well-surveyed reefs, but my main point is that one must be careful with extrapolating their research findings.
In this week's paper, the author found that in the Caribbean surrounding Panama, "there is a positive correlation between coral abundance and diversity" while the opposite, inverse relationship is found in the eastern Pacific Panamanian coast. The author found that Caribbean scleractinian (hard, reef-building) corals are not as competitive as Pacific corals. This means that as coral numbers (abundance) increases, so too does coral diversity (# species) because there are no individual corals that are particularly aggressive to the point where they can outcompete their neighbors and create monospecific stands. In the Pacific, on the other hand, there are corals that are very competitive such that as abundance (coral numbers) increase, the chances that a few very competitive corals make up a larger proportion of the faunal community increases. As a result, coral diversity does not increase with increasing abundance.
The only exceptions to the inverse relationship in the Pacific (that the author found) were during cases of disturbance, such as after hurricanes or when Acanthaster planci (crown of thorns seastars) predated large areas of corals, paving the way for recolonization by other coral recruits.
In Pacific Panama, the coral Pocillopora damicornis was the strongest competitor on their reefs, though elsewhere in the Pacific (such as in the coral triangle), Acropora spp. tend to be the dominant competitors.
The author also found that "although the relative abundances of the coral species change markedly [in Pacific Panama following crown of thorns seastar predation events], for the most part, the order of abundance does not." Hierarchies of dominance followed levels of competitiveness among various coral species.
These results contrast with those of the Caribbean, where "except for several acroporids, which calcify relatively rapidly, no consistent relation exists between a coral's calcification rate and its prevalence on a Jamaican reef."
The reasons why such a dynamic occurs were succinctly summarized by the author: "In the eastern Pacific, rapid growth and high digestive dominance are present in the same species. In the Caribbean, the opposite is true: The species that calcify and grow most rapidly are the least capable of eating other species, while the species that grow most slowly are highest on the digestive dominance scale." As a result, in the Caribbean, high-diversity areas have lots of slow-growing corals that are able to protect their immediate surrounds from competitors through specialized "sweeper tentacles" that digest closely growing neighbors. In the Pacific, fast-growing and competitive corals outcompete slower-growing taxa to the point where areas of high-diversity tend to be lacking in highly competitive species.
Hopefully by revisiting this classic paper, some good principles can be applied to now-extensive global coral assemblage data to determine how extensive the results of this limited study apply.
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