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Research Question
How do culture, social aspects, and environment affect the evolution of dolphin species?

Annotated Bibliography
1. Cantor, M., & Whitehead, H. (2013). The interplay between social networks and culture: theoretically and among whales and dolphins. Philosophical Transactions of The Royal Society B: Biological Sciences, 368. doi: 10.1098/rstb.2012.0340

This article discusses, both in general and with specific examples of dolphins and humpback whales, the importance of culture and group behavior in establishing phenotypes. In the study of bottlenose dolphins, individuals preferred to stick to dolphins with the same socially learned foraging behavior. Therefore, this creates a social network and further leads to possible evolution of the dolphins based on social relations.

2. Krutzen, M., Kreicker, S., Macleod, C. D., Learmonth, J., Kopps, A. M., Walsham, P., & Allen, S. J. (2014). Cultural transmission of tool use by Indo-Pacific bottlenose dolphins (Tursiops sp.) provides access to a novel foraging niche. Proceedings of the Royal Society B: Biological Sciences, 281. doi: 10.1098/rspb.2014.0374

This article explores how the culture of tool use can impact evolution, and it proceeds to use a study of ‘sponger’ vs. ‘nonsponger’ dolphins. ‘Sponger’ dolphins use ocean sponges during foraging. After a fatty acid analysis on a group of dolphins, the results revealed major differences in diet between the ‘spongers’ and ‘nonspongers,’ even when they looked for food in the same deep channels. This indicates that tool use allows dolphins to use a new niche, which could further cause an evolutionary impact.

3. Louis, M., Viricel, A., Lucas, T., Peltier, H., Alfonsi, E., Berrow, Simon, … Simon-Bouhet, B. (2014). Habitat-driven population structure of bottlenose dolphins, Tursiops truncatus, in the North-East Atlantic. Molecular Ecology, 23, 857-874. doi: 10.1111/mec.12653

Highly mobile animals can genetically differentiate based on different environments and niche specializations. By doing a large-scale genetic study of bottlenose dolphins in the North-East Atlantic, two ecotypes (coastal vs. pelagic) have been found with different population structures and traits. This divergence is most likely due to varying habitats, specializations, and social organization of the dolphins.

4. Moura, A. E., Natoli, A., Rogan, E., & Hoelzel, A. R. (2012). Atypical panmixia in a European dolphin species (Delphinus delphis): implications for the evolution of diversity across oceanic boundaries. Journal of Evolutionary Biology, 26, 63-75. doi: 10.1111/jeb.12032

Even though an ocean environment does not have as many geographic boundaries, differences in population structure between regions have been found, using the European coastline dolphins as an example. Through a widespread genetic study of the European common dolphin, a divergence was seen between the eastern and western Mediterranean regions. This may be partially due to a recent population decline of the eastern Mediterranean population. Overall, unusual patterns in this area’s population structure compared to other common dolphins in the world suggests ecological specialization for dolphins in this region.

5. Stanton, M. A., & Mann, J. (2012). Early Social Networks Predict Survival in Wild Bottlenose Dolphins. PLoS One, 7. doi: 10.1371/journal.pone.0047508

This article explores how social networks, even early in life, can affect evolution and fitness of bottlenose dolphins. In a longitudinal study, a relationship was observed between the social network of male calves and their survival rate. Male calves that died early tended to be close to the juvenile males, more so than the surviving male calves. This could possibly indicate that juvenile males inflict a fitness cost on the male calves. Overall, selection can act on social bonds, whether detrimental or beneficial, early in life to create an evolution of sorts.

Suggestions to Another Article
Suggestions:

https://en.wikipedia.org/wiki/Evolution_of_cetaceans

1. Since there is a section about early baleen whales and early dolphins, it may be a good idea to add a section about early porpoises since they're also a part of the Cetaceans. In general, too, porpoises are barely discussed in the article.

2. In the "Early Echolocation" section, it may be useful for readers to have more background information about echolocation and why it has been so helpful for Cetaceans. Currently, the section discusses where echolocation probably originated, but information about why echolocation stuck around to modern Cetaceans and how it developed/evolved over time is important to include as well.

3. In the "Skeletal Evolution" section, more information and research should be included. The current information seems disconnected, short, and lacking in research evidence. Skeletal evolution is one of the biggest evolutionary topics for Cetaceans, so expanding and organizing this section would probably be useful for readers.

Addition to Article (Talk Page because editing was not allowed):

https://en.wikipedia.org/wiki/Dolphin

I was thinking about adding this sentence to the end of the 3rd paragraph in the "Social Behavior" section.

Culture and social networks have played a large role in the evolution of dolphins as well, as shown in recent research showing dolphins preferring other individuals with the same socially-learned behaviors, including the foraging behavior discussed above.

Final Paper
FINAL DRAFT STARTS HERE

Cultural, Social, and Environmental Effects on the Evolution of Dolphins

When discussing evolution, the genetic aspect seems to come to mind first, and people can easily fall under the impression that evolution is purely due to genetics. However, once investigated further, it is realized that evolution can be affected by other elements as well, such as cultural, social, and environmental factors. Moreover, organisms in tightknit social groups tend to be heavily influenced by these outside factors due to their profound prevalence. For instance, dolphin species are known to be extremely social mammals, and they have long been evolving based on numerous cultural, environmental, and social factors rather than just pure genetics.

This topic concerning the cultural, social, and environmental effects on dolphin evolution is strongly related to evolutionary biology. Both subjects deal with how organisms change over time and the mechanisms of this evolution. The differences are that the dolphin topic focuses on a specific organism and only a few mechanisms for its evolution instead of using a broad, overarching perspective. Learning more about this subject through research is obviously important in order for scientists to learn more about dolphins, their interactions, and their evolution. However, this information can possibly be applied to other organisms that live in socially tightknit groups as well, including humans. As a result, learning more about this topic can lead to new revelations about the cultural, social, and environmental effects on the evolution of humans.

The first major factor of evolution in dolphins is culture. First of all, culture is defined as group-specific behavior transferred by social learning (Cantor and Whitehead 2013). One of the best examples for dolphins where culture affects evolution involves tool use and foraging. Generally speaking, whether or not a dolphin uses a tool affects their eating behavior, which therefore causes differences in diet. Also, using a tool allows a new niche and new prey to open up for that particular dolphin. Due to these differences, fitness levels change within the dolphins of a population, which further causes evolution to occur in the long run. For example, based on recent research, the population of Indo-Pacific bottlenose dolphins (Tursiops sp.) around Shark Bay of Western Australia can be divided into spongers and nonspongers. Spongers put sponges on their noses as a protective means against abrasions from sharp objects, stingray barbs, or toxic organisms. The sponges also help the dolphins target fish without swim bladders, since echolocation cannot detect these fish easily against a complex background. Spongers also specifically forage in deep channels, but nonspongers are found foraging in both deep and shallow channels (Krutzen et al. 2014). Thus, since the deep channels have spongers and nonspongers in the same geological area, this is an example of sympatry and ecological character displacement. Moreover, this tool use seems to have a female bias, since more than 60 percent of all females in the area use sponges. However, a significant amount of males also use sponges as well, with numbers reporting up to 50 percent of males born to spongers becoming involved in this tool use too (Krutzen et al. 2014). It has also been discovered that this foraging behavior seems to be passed on from mother to daughter/son most of the time (Cantor and Whitehead 2013). Therefore, since this is a group behavior being passed down by social learning, this tool use is considered a culture.

In a recent experiment with these Shark Bay populations of dolphins, researchers wanted to find out whether tool use incurred differences in diet, which could possibly show a new niche opening up for the tool users. The researchers compared data from the East and West Gulf of Shark Bay, deep and shallow channels, and sponger vs. nonsponger dolphins. In order to test differences of diet, they took superficial blubber samples and performed a fatty acid analysis. Overall, the researchers found the fatty acid analyses to differ between West and East Gulf, which makes sense since the two areas have different food sources for the inhabitants. However, when comparing data from within the West Gulf, the spongers vs. the nonspongers in the deep channels had very different fatty acid analyses even though the habitat is the same. Meanwhile, nonspongers from deep and shallow channels had similar data. This suggests that sponging was the cause of the different data and not the deep vs. shallow channels. Sponging opened up a new niche for the dolphins and allowed them access to new prey, thereby causing long-term diet changes (Krutzen et al. 2014). By causing dolphins within a population to have different food sources, there is less intrapopulation competition for resources, again showing ecological character displacement. As a result, carrying capacity actually increases since the entire population does not depend on one food source. Meanwhile, the fitness levels within the population also change, thus allowing evolution to act on this culture.

In addition, social networks within a population can affect culture, further leading to evolution as well. In fact, the social structure of a population and the transmission of information (social learning and culture) directly correlate with each other. Social structure forms groups or modules that interact with one another, and this allows for cultural traits to emerge, flow, and evolve. This relationship is especially seen in the bottlenose dolphin populations in southwestern Australia, who have been known to beg for food from fishermen. Research shows that this begging behavior spread through the population due to two types of learning: individual (dolphins spending time around boats) and social (dolphins spending time with other dolphins who express begging behavior) (Cantor and Whitehead 2013). This further displays how the social structure (who/where the dolphin spends time) affects the individual’s behavior and overall culture. In the opposite way, culture can affect social structure by causing behavior matching and assortative mating. This basically means that individuals with a certain culture are more likely to associate/mate with individuals using the same behaviors rather than a random individual, thus influencing social groups and structure. For example, the sponger dolphins discussed earlier preferentially stick with other spongers (Cantor and Whitehead 2013). This behavior matching is a major driver for the population’s social structure. As another example, some bottlenose dolphins in Moreton Bay of Australia followed prawn trawlers to feed on their debris, while other dolphins in the same population did not follow them. The dolphins preferentially associated with individuals with same behavior even though they all lived in the same habitat. Later on, prawn trawlers were no longer present, and the dolphins integrated into one social network after a couple of years (Cantor and Whitehead 2013). Overall, the dolphins’ behavior and culture had a major effect on their social structure, especially exemplified by the integration of social networks after culture no longer differed. All of these experiments emphasize the relationship between culture and social structure, and the examples also help to show how they affect evolution together.

Without relating to culture, social networks can still affect and cause evolution on their own by impending fitness differences on individuals (Frere et al. 2010). One example of this is seen in a longitudinal study performed on bottlenose dolphins. The study analyzed the early social bonds formed by male calves and their resulting survival rate. According to the data, male calves had a lower survival rate if they had stronger bonds with juvenile males. However, when other age and sex classes were tested, their survival rate did not significantly change (Stanton and Mann 2012). This suggests that juvenile males impose a social stress on their younger counterparts, thus lowering the fitness of the male calves and reducing survival rates. It has been noted that juvenile males commonly perform acts of aggression, dominance, and intimidation against the male calves, so this is probably the social stress decreasing the calves’ fitness (Stanton and Mann 2012). Overall, selection seems to act on these social bonds early in the calves’ lives, thus causing the differences in survival rates past age 10 and furthermore evolution. In another experiment of bottlenose dolphins in the East Gulf of Shark Bay, the fitness of female dolphins was influenced by their social bonds. Their fitness was measured by the success of their own calves. The research revealed differences in fitness in the population, and two possible explanations were suggested. First of all, the differences could be due to social learning (whether or not the mother passed on her knowledge of reproductive ability to the calves). It could also be due to the strong association between mother dolphins in the population; by sticking in a group, an individual mother does not need to be as vigilant all the time for predators (Frere et al. 2010). This is a prime example of homophily as well, since the dolphins are associating with individuals that are similar to themselves. Overall, this homophily and social learning seem to increase fitness of female dolphins, thus causing an selection for these traits and evolution.

Lastly, evolution can also be affected by the environment in multiple ways. Starting with the Yangtze River dolphin (Lipotes vexillifer), which is nearly extinct at this point, recent genome sequences revealed that these dolphins lack single nucleotide polymorphisms in the baiji genome. After reconstructing the history of the baiji genome for the Yangtze River dolphin, researchers found that the major decrease in genetic diversity occurred most likely because of a bottleneck event during the last deglaciation. During this time period, sea levels were rising while global temperatures were decreasing. Other historical climate events can be correlated and matched with the genome history of the Yangtze River dolphin as well (Zhou et al. 2013). This shows how global and local climate change can drastically affect a genome, leading to changes in fitness, survival, and evolution of a species. Thus, evolutionary history and climate history can be linked to each other in certain species.

Environment has also affected populations of the European common dolphin (Delphinus delphis) in the Mediterranean and bottlenose dolphins (Tursiops spp.) in the Northeast Atlantic and elsewhere. For example, the European common dolphins in the Mediterranean have differentiated into two types: western and eastern. According to research, this seems to be due to a recent bottleneck as well, which drastically decreased the size of the eastern Mediterranean population. Also, the lack of population structure between the western and eastern regions seems contradictory of the distinct population structures between other regions of dolphins, proving again of their differentiation (Moura et al. 2012). Even though the dolphins in the Mediterranean area had no physical barrier between their regions, they still differentiated into two types. This indicates that physical barriers are not the only factor for forming distinct traits, but ecology and biology are significant factors as well. Therefore, the differences between the eastern and western dolphins most likely stems from highly specialized niche choice rather than just physical barriers. Through this, environment plays a large role in the differentiation and evolution of this dolphin species.

As for the bottlenose dolphins, their divergence and speciation within the genus has been largely due to climate and environmental changes over history. According to research, the divisions within the genus correlate with periods of rapid climate change. For example, the changing temperatures could cause the coast landscape to change, niches to empty up, and opportunities for separation to appear (Moura et al. 2013). In the Northeast Atlantic specifically, genetic evidence suggests that the bottlenose dolphins have differentiated into a coastal and pelagic type. Divergence seems most likely due to a founding event where a large group separated. Following this event, the separate groups adapted accordingly and formed their own niche specializations and social structures. These differences caused the two groups to diverge and to remain separated (Louis et al. 2014). As one can see, environment has strongly affected the diversification, separation, and evolution of multiple dolphin species.

Overall, genetics is not the only mechanism for evolution, but culture, social structure, and environment have a huge impact on evolution as well. One of the best organisms to use as an example is the dolphin due to its extremely social behavior and its group-living conditions. Numerous experiments have been performed to show evolutionary changes in dolphins due to tool use (culture), social bonds (social aspects), and climate and temperature changes (environment). Now that the social, cultural, and environmental mechanisms for evolution have been identified, the next step is to determine how this information can be applied to other social organisms and their evolution, especially with humans.

Literature Cited

Cantor, M., & Whitehead, H. (2013). The interplay between social networks and culture: theoretically and among whales and dolphins. Philosophical Transactions of The Royal Society B: Biological Sciences, 368. doi: 10.1098/rstb.2012.0340

Frere, C. H., Krutzen, M., Mann, J. Connor, R. C., Bejder, L., & Sherwin, W. B. (2010). Social and genetic interactions drive fitness variation in a free-living dolphin population. Proceedings of the National Academy of Sciences of the United States of America, 107, 19949-19954. doi: 10.1073/pnas.1007997107

Krutzen, M., Kreicker, S., Macleod, C. D., Learmonth, J., Kopps, A. M., Walsham, P., & Allen, S. J. (2014). Cultural transmission of tool use by Indo-Pacific bottlenose dolphins (Tursiops sp.) provides access to a novel foraging niche. Proceedings of the Royal Society B: Biological Sciences, 281. doi: 10.1098/rspb.2014.0374

Louis, M., Viricel, A., Lucas, T., Peltier, H., Alfonsi, E., Berrow, S., … Simon-Bouhet, B. (2014). Habitat-driven population structure of bottlenose dolphins, Tursiops truncatus, in the North-East Atlantic. Molecular Ecology, 23, 857-874. doi: 10.1111/mec.12653

Moura, A. E., Natoli, A., Rogan, E., & Hoelzel, A. R. (2012). Atypical panmixia in a European dolphin species (Delphinus delphis): implications for the evolution of diversity across oceanic boundaries. Journal of Evolutionary Biology, 26, 63-75. doi: 10.1111/jeb.12032

Moura, A. E., Nielsen, S. C. A., Vilstrup, J. T., Moreno-Mayar, J. V., Gilbert, M. T. P., Gray, H. W. I., … Hoelzel, A. R. (2013). Recent Diversification of a Marine Genus (Tursiops spp.) Tracks Habitat Preference and Environmental Change. Systematic Biology, 62 (6), 865-877. doi: 10.1093/sysbio/syt051

Stanton, M. A., & Mann, J. (2012). Early Social Networks Predict Survival in Wild Bottlenose Dolphins. PLoS One, 7. doi: 10.1371/journal.pone.0047508

Zhou, X., Sun, F., Xu, S., Fan, G., Zhu, K., Liu, X., … Yang, G. (2013). Baiji genomes reveal low genetic variability and new insights into secondary aquatic adaptations. Nature Communications, 4. doi: 10.1038/ncomms3708

FINAL DRAFT ENDS HERE

Edit to Existing Wikipedia Article
https://en.wikipedia.org/wiki/Evolution_of_cetaceans

Modern Evolution of Cetaceans (section)

(Added this last sentence to first paragraph of the section) For dolphins particularly, the largest non-genetic effects on their evolution seem to be due to culture, social structure, and environmental factors.

(Added the following text and subheadings)

Culture
First of all, culture is defined as group-specific behavior transferred by social learning. One of the best examples for dolphins where culture affects evolution involves tool use and foraging. Generally speaking, whether or not a dolphin uses a tool affects their eating behavior, which therefore causes differences in diet. Also, using a tool allows a new niche and new prey to open up for that particular dolphin. Due to these differences, fitness levels change within the dolphins of a population, which further causes evolution to occur in the long run.

Indo-Pacific Bottlenose Dolphins
Based on recent research, the population of Indo-Pacific bottlenose dolphins (Tursiops sp.) around Shark Bay of Western Australia can be divided into spongers and nonspongers. Spongers put sponges on their noses as a protective means against abrasions from sharp objects, stingray barbs, or toxic organisms. The sponges also help the dolphins target fish without swim bladders, since echolocation cannot detect these fish easily against a complex background. Spongers also specifically forage in deep channels, but nonspongers are found foraging in both deep and shallow channels. It has also been discovered that this foraging behavior seems to be passed on from mother to daughter/son most of the time. Therefore, since this is a group behavior being passed down by social learning, this tool use is considered a culture.

In a recent experiment with these Shark Bay populations, researchers compared data from the East and West Gulf of Shark Bay, deep and shallow channels, and sponger vs. nonsponger dolphins. In order to test differences of diet, they took superficial blubber samples and performed a fatty acid analysis. Overall, the researchers found the fatty acid analyses to differ between West and East Gulf, which is simply due to the two areas having different food sources. However, when comparing data from within the West Gulf, the spongers vs. the nonspongers in the deep channels had very different fatty acid analyses even though the habitat is the same. Meanwhile, nonspongers from deep and shallow channels had similar data. This suggests that sponging was the cause of the different data and not the deep vs. shallow channels. Sponging opened up a new niche for the dolphins and allowed them access to new prey, thereby causing long-term diet changes. By producing different food sources within a population, there is less intrapopulation competition for resources, showing ecological character displacement. As a result, carrying capacity actually increases since the entire population does not depend on one food source. Meanwhile, the fitness levels within the population also change, thus allowing evolution to act on this culture.

Social Structure
In addition, social networks within a population correlate with culture, further leading to evolution as well. Social structure forms groups that interact with one another, and this allows for cultural traits to emerge, flow, and evolve. This relationship is especially seen in the bottlenose dolphin populations in southwestern Australia, who have been known to beg for food from fishermen. Research shows that this begging behavior spread through the population due to two types of learning: individual (dolphins spending time around boats) and social (dolphins spending time with other dolphins who express begging behavior). This further displays how the social structure (who/where the dolphin spends time) affects the individual’s behavior and overall culture.

In the opposite way, culture can impact social structure by causing behavior matching and assortative mating. Individuals with a certain culture are more likely to associate/mate with individuals using the same behaviors rather than a random individual, thus influencing social groups and structure. For example, the sponger dolphins of Shark Bay preferentially stick with other spongers. As another example, some bottlenose dolphins in Moreton Bay of Australia followed prawn trawlers to feed on their debris, while other dolphins in the same population did not follow them. The dolphins preferentially associated with individuals with same behavior even though they all lived in the same habitat. Later on, prawn trawlers were no longer present, and the dolphins integrated into one social network after a couple of years. The integration of social networks after culture no longer differed exemplifies the major effect of culture on social structure.

Without relating to culture, social networks can still affect and cause evolution on their own by impending fitness differences on individuals. In a longitudinal study performed on bottlenose dolphins, the early social bonds formed by male calves and their resulting survival rates were analyzed. According to the data, male calves had a lower survival rate if they had stronger bonds with juvenile males. However, when other age and sex classes were tested, their survival rate did not significantly change. This suggests that juvenile males impose a social stress on their younger counterparts. In fact, it has been documented that juvenile males commonly perform acts of aggression, dominance, and intimidation against the male calves. Thus, the fitness and survival rates of these male calves decrease, demonstrating how selection acts on these social bonds early in the calves’ lives.

In another experiment of bottlenose dolphins in the East Gulf of Shark Bay, fitness of female dolphins was measured by the success of their own calves. The research revealed differences in fitness within the population, and two possible explanations due to social bonds were suggested. First of all, the differences could be due to social learning (whether or not the mother passed on her knowledge of reproductive ability to the calves). It could also be due to the strong association between mother dolphins in the population; by sticking in a group, an individual mother does not need to be as vigilant all the time for predators. Overall, this social learning and homophily seem to increase fitness of female dolphins, thus causing an selection for these traits and evolution.

Environmental Factors
Lastly, the environment has strongly affected the diversification, separation, and evolution of multiple dolphin species.

Yangtze River Dolphin
Recent genome sequences revealed that the Yangtze River dolphin (Lipotes vexillifer) lacks single nucleotide polymorphisms in the baiji genome. After reconstructing the history of the baiji genome for this dolphin species, researchers found that the major decrease in genetic diversity occurred most likely due to a bottleneck event during the last deglaciation. During this time period, sea levels were rising while global temperatures were decreasing. Other historical climate events can be correlated and matched with the genome history of the Yangtze River dolphin as well. This shows how global and local climate change can drastically affect a genome, leading to changes in fitness, survival, and evolution of a species.

European Common Dolphin
The European common dolphins (Delphinus delphis) in the Mediterranean have differentiated into two types: western and eastern. According to research, this seems to be due to a recent bottleneck as well, which drastically decreased the size of the eastern Mediterranean population. Also, the lack of population structure between the western and eastern regions seems contradictory of the distinct population structures between other regions of dolphins, proving again of their differentiation. Even though the dolphins in the Mediterranean area had no physical barrier between their regions, they still differentiated into two types due to ecology and biology. Therefore, the differences between the eastern and western dolphins most likely stems from highly specialized niche choice rather than just physical barriers. Through this, environment plays a large role in the differentiation and evolution of this dolphin species.

Bottlenose Dolphin
The divergence and speciation within this genus has been largely due to climate and environmental changes over history. According to research, the divisions within the genus correlate with periods of rapid climate change. For example, the changing temperatures could cause the coast landscape to change, niches to empty up, and opportunities for separation to appear. In the Northeast Atlantic specifically, genetic evidence suggests that the bottlenose dolphins have differentiated into a coastal and pelagic type. Divergence seems most likely due to a founding event where a large group separated. Following this event, the separate groups adapted accordingly and formed their own niche specializations and social structures. These differences caused the two groups to diverge and to remain separated.