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What is the evolutionary purpose of the eusociality in mole rats?

Burda, H., & Kawalika, M. (1993). Evolution of eusociality in the Bathyergidae. The case of the giant mole rats (Cryptomys mechowi). Die Naturwissenschaften, 80, 5, 235-7. This article contains the research findings on the evolution of eusociality of mole rats in Zambia. This was done through analyzing their living patterns as well as their eating and reproductive, or breeding, characteristics.

Burland, T., Bennett, N., Jarvis, J., & Faulkes, C. (2002). Eusociality in African mole-rats: new insights from patterns of genetic relatedness in the Damaraland mole-rat (Cryptomys damarensis). Proceedings: Biological Sciences, 269, 1495, 1025-1030. The DNA and microsattelites of certain colonies of mole rats in Africa were sampled. The offspring were compared to possible mothers to compare the genetic relatedness of the colony.

Kalamatianos, T., Faulkes, C. G., Oosthuizen, M. K., Poorun, R., Bennett, N. C., & Coen, C. W. (2010). Telencephalic binding sites for oxytocin and social organization: A comparative study of eusocial naked mole-rats and solitary cape mole-rats. Journal of Comparative Neurology, 518, 10, 1792-1813. The sociality of naked mole rats and cape mole rats was compared. This was done by determining the amount of oxytocin receptor binding in both species. The amount of oxytocin binding as well as other processes provided insight to the social behavior of the naked mole rats.

Faulkes, C. G., Verheyen, E., Verheyen, W., Jarvis, J. U. M., & Bennett, N. C. (2004). Phylogeographical patterns of genetic divergence and speciation in African mole-rats (Family: Bathyergidae). Molecular Ecology, 13, 3, 613-629.

Mitochondrial DNA was used to trace the phylogeny of the different populations of mole rats in Africa. Using the information from the mDNA,two phylogenetic trees were produced.

Jarvis, J. U. M., & Bennett, N. C. (1993). Eusociality has evolved independently in two genera of bathyergid mole-rats — but occurs in no other subterranean mammal. Behavioral Ecology and Sociobiology, 33, 4, 253-260. Mole rats were captured and released in an effort to understand their reproductive patters and the evolution of their eusociality traits. During this, it was found that there was a division of reproductive behavior, overlap in two generations, and cooperative care for the young.

Oct 1st Assignment https://en.wikipedia.org/wiki/Naked_mole_rat

addition to page There are two main types of worker, the "frequent workers" who frequently perform tasks such as foraging and nest building and "infrequent workers" that show role overlap with the "frequent workers" but perform at a much slower rate

citation Eusociality in a Mammal: Cooperative Breeding in Naked Mole-Rat Colonies. J. U. M. Jarvis. Science, New Series, Vol. 212, No. 4494 (May 1, 1981), pp.571-573. Published by: American Association for the Advancement of Science. Article Stable URL: http://www.jstor.org.proxy.lib.ohio-state.edu/stable/1686202

suggestions 1. I'm not finding where the larger Naked Mole Rats actually guard the nest. Possibly cite or change to something more accurate 2. Possibly provide some information on research that has been done to determine the eusocial characteristics in mole rats 3. Also change the females are temporarily sterile to something along the lines that most females will most likely never breed and that their ovaries appear to be unactive

=Final Paper= Evolution of Eusociality in Mole Rats The purpose of this paper is to explain the evolution of eusociality in naked mole rats. This is an interesting topic because not all mole rats are eusocial. Actually, most species of the mole rats are solitary creatures (Burland et al., 2002). To begin, one may question whether or not this is a trait that has diverged into just these two species of mole rats or something that has occurred between the two as a result of the environment or other factors. If it is something that has been caused by environmental factors, one may question what environmental factors have caused these mole rats to respond in such a manner. There is some suggestion that allopatric speciation could have caused the development of this behavior. Physical characteristics of individuals within these populations of eusocial mole rats could possibly provide answers as to why these two specific species of have developed this certain social behavior. Along with physical characteristics, it may be of interest to see how those characteristics correspond with the “positions” held within the colony. After discussing the above mentioned, it can be seen what aspects of evolution have caused this interesting trait of eusociality to appear in mole rats. There are two different species of mole rats that are said to be eusocial. Eusociality can be best illustrated by the example of honeybees. There is the “queen bee” that produces all of the offspring and there are also the worker bees, which go out and find food for the rest of the colony as well as help with building and other tasks around the hive. These characteristics are very similar to those of the eusocial colonies of mole rats. These mole rats have a queen and workers that all inhabit their colonies. Of all mammals that inhabit the earth, only mole rats have been known to be eusocial (Burda and Kawalika, 1993). These eusocial traits have mainly been seen in the Naked Mole Rat and the Damaraland Mole Rat. Even though these two species, because of their eusocial behaviors, seem to be very close in relation, it is believed that both the Naked and Damaraland mole rats gained their behavior through independent evolutionary occurrences (Bennett and Young, 2010). Several studies show that eusocial characteristics have been gained or lost more than once during the evolution of mole rats in their native land of Africa (Faulkes et al., 2004). There is evidence, from molecular phylogenies, that proposes that both the Naked Mole Rat and the Damaraland Mole Rat species have diverged throughout the evolution of the family of mole rats. The breeding habits of these species also seem to have appeared independently on two or more different occasions (Burland et al., 2002). Another example of the divergence of the eusocial behavior mole rats can be seen in the research done between eusocial Naked Mole Rats and solitary Cape Mole Rats. During this research, it was found that there was a significant difference in telencephalic oxytocin receptor binding in the two species. There were expressive differences of the OTR binding sites between the Naked Mole Rats and the Cape Mole rats which may aid in the understanding of their social tendencies. Along with these findings, the scientists that performed the experiment also found that the OTR binding found in certain areas of the Naked Mole Rat may correspond with their eusocial behavior as well as their tendency to form reproductive attachments (Kalamatianos et al., 2010) It is speculated that the environment in which these mole rats reside coincides with their eusocial behavior. Their habitat consists of little to no rainfall and very low food density. Because of the low food density, there are high costs to reproducing while foraging for food as well as high energy costs of burrowing to provide shelter and protection (Burland et al., 2002). This is a prime example of allopatric speciation. These particular mole rats have been geographically isolated by harsh conditions. This could cause an evolutionary divergence from the other mole rat species. As mentioned earlier, the makeup of a mole rat colony is similar to that of bees or ants. In the case of mole rats, there is a division of reproductive labor. This division consists of one actively reproducing female and several reproducing males. The non-reproducing females have appeared to be reproductively suppressed, meaning the ovaries do not fully mature. They also do not have the same levels of certain hormones as the reproducing females. The males, on the other hand, do not show much difference in their hormone concentrations. In experiments where the reproductive female was removed or died, one of the non-reproducing females would take over and become sexually active. Along with the reproducing female and reproducing males, there are also non-reproductive individuals that make up the colony. It can be said that there are two “jobs” that these individuals perform. The groups that perform the jobs of infrequent or frequent workers are made up of both the non-reproducing male and non-reproducing female. There is also cooperative care that occurs for the pups of the reproducing female. This occurs through the workers keeping the pups from straying, foraging for food, grooming, contributing to extension of tunnels, and keeping them warm (Bennett and Jarvis, 1993). One reason for this social structure may be because of altruism. This act of selflessness can be seen by both the queen and the workers. They are both giving up their energy and resources for the better of the colony. Now that the structure of the mole rat eusocial system has been discussed, the specifics of each of the reproducing individuals can be discussed in further detail. Reproducing females become the dominant female, usually, by founding new colonies, fighting for the dominant position, or taking over once the reproducing female dies. These reproducing females tend to have longer bodies than that of their non-reproducing counter parts of the same skull width. Interestingly enough, the measurements of females before they became reproductive and after show significant increases in body size. It is believed that this trait does not occur due to pre-existing morphological differences but to the actual attainment of the dominant female position (Young and Bennett, 2010). As with the reproductive females, the reproductive males also appear to be bigger in size than their non-reproducing counterparts but not as much so as in the case of the females. These males also have visible outlines of the testes through the skin of their abdomens. Unlike the females, there are usually multiple reproducing males (Bennett and Jarvis, 1993). A problem that could be of concern with only one reproductive female and several reproductive males is inbreeding. In some colonies, the costs of avoiding inbreeding far outweigh the benefits of outbreeding. The research done by Deborah Ciszek, of the University of Michigan, takes a look at this potential problem. She provided new evidence showed that some colonies are founded by unrelated Mole Rats. In her research, it was found the higher weight and neck width would provide information as to which mole rat would become one of the reproductive ones. In cases where siblings of the same sex had the opportunity to become reproductive individuals, the heavier individuals of the two became reproductive. Ciszek also observed that no non-reproducing females took place in any kind of mounting with that of reproducing males. One of her more interesting findings was that there was a higher proportion of reproductive males to be unknown distant relatives to the reproductive female. In her experimental setting, she found that there was consistent outbreeding to mole rats that were not closely related to them. This shows that mole rats are able to tell the difference between related and unrelated mole rats of the same colony but in the wild it would be very hard for this to take place, because of the lack of outside mole rats venturing into the colony. It would require mole rats to have traits that allow for successful survival during dispersal and to avoid predation. After taking this into consideration, it can be seen that there are greater benefits for siblings to become workers and that siblings would suffer from inbreeding depression associated with the inbreeding of closely related individuals (Ciszek, 1999). There are several evolutionary forces at work here within the eusocial mole rat colonies. One great example of evolution here is allopatric speciation. Allopatric speciation occurs when populations of the same species become separated from each other, therefore preventing genetic flow between the two populations. Because of this separation, the two populations eventually evolve into separate species from one another. This might be one of the causes for the eusocial characteristics that have arose in the two different mole rat species. If they migrated away from their main population and then became isolated, there is a possibility that they eventually evolved into the species that they are today and their eusociality is a part of that allopatric speciation evolution. Another evolutionary force that can be seen within the mole rats is altruism. Altruism is when a member of the group practices selflessness for the greater good of the colony. This is seen in the case of the reproducing female as well as the worker mole rats. They reproducing female uses her energy to provide new members to the population of the colony. At the same time, the worker mole rats use their energy to burrow, find food, and help nurture the new pups until they are able to help as well. As seen above, the evolution of eusociality in mole rats could be contributed to multiple different causes. Allopatric speciation, altruism, and inbreeding depression are all evolutionary forces at work in the eusocial behavior of the mole rats. Each, in their own way, appears to play its own role in the two species of mole rats arriving at their current social structures. References Burda, H., & Kawalika, M. (1993). Evolution of eusociality in the Bathyergidae. The case of the giant mole rats (Cryptomys mechowi). Die Naturwissenschaften, 80, 5, 235-7. Burland, T., Bennett, N., Jarvis, J., & Faulkes, C. (2002). Eusociality in African mole-rats: new insights from patterns of genetic relatedness in the Damaraland mole-rat (Cryptomysdamarensis). Proceedings: Biological Sciences, 269, 1495, 1025-1030. Kalamatianos, T., Faulkes, C. G., Oosthuizen, M. K., Poorun, R., Bennett, N. C., & Coen, C. W. (2010). Telencephalic binding sites for oxytocin and social organization: A comparative study of eusocial naked mole-rats and solitary cape mole-rats. Journal of Comparative Neurology, 518, 10, 1792-1813. Faulkes, C. G., Verheyen, E., Verheyen, W., Jarvis, J. U. M., & Bennett, N. C. (2004). Phylogeographical patterns of genetic divergence and speciation in African mole-rats (Family: Bathyergidae). Molecular Ecology, 13, 3, 613-629. Jarvis, J. U. M., & Bennett, N. C. (1993). Eusociality has evolved independently in two genera of bathyergid mole-rats — but occurs in no other subterranean mammal. Behavioral Ecology and Sociobiology, 33, 4, 253-260. J. U. M. Jarvis. Eusociality in a Mammal: Cooperative Breeding in Naked Mole-Rat Colonies. Science, New Series, Vol. 212, No. 4494 (May 1, 1981), pp.571-573. Published by: American Association for the Advancement of Science. Ciszek, D. (December 31, 1999). New colony formation in the highly inbred eusocial naked mole-rat: outbreeding is preferred. Behavioral Ecology, 11, 1, 1. Young, A. J., & Bennett, N. C. (November 01, 2010). Morphological Divergence of Breeders and Helpers in Wild Damaraland Mole Rat Societies. Evolution, 64, 11, 3190-3197.

Final Edits
https://en.wikipedia.org/wiki/Naked_mole-rat

Roles
The non-reproducing females have appeared to be reproductively suppressed, meaning the ovaries do not fully mature. They also do not have the same levels of certain hormones as the reproducing females. The males, on the other hand, do not show much difference in their hormone concentrations. In experiments where the reproductive female was removed or died, one of the non-reproducing females would take over and become sexually active. Along with the reproducing female and reproducing males, there are also non-reproductive individuals that make up the colony. It can be said that there are two “jobs” that these individuals perform. The groups that perform the jobs of infrequent or frequent workers are made up of both the non-reproducing male and non-reproducing female. There is also cooperative care that occurs for the pups of the reproducing female. This occurs through the workers keeping the pups from straying, foraging for food, grooming, contributing to extension of tunnels, and keeping them warm.

Size
Reproducing females become the dominant female, usually, by founding new colonies, fighting for the dominant position, or taking over once the reproducing female dies. These reproducing females tend to have longer bodies than that of their non-reproducing counter parts of the same skull width. Interestingly enough, the measurements of females before they became reproductive and after show significant increases in body size. It is believed that this trait does not occur due to pre-existing morphological differences but to the actual attainment of the dominant female position. As with the reproductive females, the reproductive males also appear to be bigger in size than their non-reproducing counterparts but not as much so as in the case of the females. These males also have visible outlines of the testes through the skin of their abdomens. Unlike the females, there are usually multiple reproducing males