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Changes were made to the Wikipedia article below under the coevolution section. References were updated as well.

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

EEOB 3310 – Evolution Thursday, 9:10; David Salazar-Valenzuela FINAL DRAFT STARTS HERE

Coevolution of Yucca Plants and Yucca Moths -Taha Faridi

The coevolution of Yucca plants and their obligate pollinators the Yucca moths has been a major point of study in the evolutionary effects of mutualistic behaviors among plants and insects. The Yucca genus of plants is one of many diverse plant genera which share special mutualisms with insects to help drive fitness and genetic diversity of both organisms. Most Yucca plants are helped by such a relationship with the family of moths known as Prodoxidae or more commonly referred to as Yucca moths (Pellmyr 1996). These spanning mutualisms between Prodoxidae and Yucca plants have caused major evolutionary patterns to form around them. Current scientific studies have proposed that coevolution is major contributing factor in propelling genetic variation and reinforcing mutualistic behaviors of the Yucca plants and moths. In addition to mutualistic ones, in certain populations scientists have also seen the rise of cheater populations of moths and plants. The strength of coevolution in these scenarios can further be studied by examining phylogenies of both interacting species and analyzing genetic changes (Segraves 2008). Coevolution is particularly important in evolutionary biology as it demonstrates increased genetic variance between two organisms that have strong interactions, resulting in increased fitness generally for both species.

In an effort to further investigate the traits that have evolved as a result of coevolution O. Pellmyr and his team utilized a phylogenetic framework to observe the evolution of active pollination and specializing effects of the Yucca moths which eventually lead to the loss of nectar in the genus of Yucca plants, requiring them to have Prodoxidae moths around to reproduce. The moths in this case, specifically Tegeticula and Parategeticula, pollinate Yucca flower purposefully, and lay their eggs in the flowers. The larvae of the moths rely on Yucca seeds as nourishment and this is also cost inflicted on the plants to maintain the mutualism. After setting up a test experiment which involved pairing species of Prodoxidae with different host plants, the results have shown that moths that were able to develop a pollination-type relationship with the new plant species were more successful and would better be able to reproduce than moths that were unable to do so. (Pellmyr 1996; Groman 2000)

Another study takes a look at coevolution as a primary driver of change and diversification in the Yucca moth and the Joshua tree, more commonly known as the Yucca palm. The researchers tested this hypothesis by setting up a differential selection of two species of yucca moths and two corresponding species of Yucca palms which they pollinate. The study showed floral traits involving pollination evolved substantially more rapidly than other flower features. The study then looks at phylogeny and determines that coevolution is the major evolutionary force behind diversification in the Yucca palms when pollinated moths were present (Godsoe 2008). The researchers of the Joshua tree show that setting up phylogenetic patterns using maximum likelihood techniques, can be a powerful tool to analyze the divergence in species.

Researchers have again tried to demonstrate the absolute minimal level of evolution needed to secure a Yucca plant and moth mutualism. The researchers attempt to find an answer as to how integral coevolution was as the driving force behind various adaptions between the Yucca moth and plant species. Phylogenetic examination was also used here to reconstruct the trait evolution of the pollinating Yucca moths and their non-mutualistic variants. Certain mutualistic traits have predated the Yucca moth-plant mutualism, such as larval feeding in the floral ovary; however, it suggests that other key traits linked to pollination were indeed a result of coevolution between the two species. It is integral to reiterate here that key traits such tentacular appendages which help in pollen collection and pollinating behaviors evolved as a result of coevolution during a mutualism between moths and host plants. After collecting genetic information from dozens of differing Prodoxidae moths, including ones involved in ideal mutualisms such as Tegeticula, and mapping these extracted sequences using the Bayestraits clade forming algorithm, conclusions could be drawn about trait formation that differentiated the monophylum or clade of strict obligate pollinators in the Prodoxidae family from other moths that did not undergo mutualism (Yoder 2010).

In an effort to introduce further variance researchers created a test environment in which they shift the host of certain moths. The Y. aloifolia was introduced into the eastern United States. The results backed the idea that new host colonization of moths greatly perpetuated genetic isolation from past populations. Significant genetic differentiation as well as morphological changes was observed from the host shift (Groman 2000). This indicates that even by changing the host of mutualistic moths, mutualism reemerges and genetic change is amplified. It is also indicated that the adaptability of host changing in moths shows a gradual affinity towards mutualistic relationships for the moths.

Throughout the extensive coevolutionary history between Yucca plants and moths, cheating has become an issue in certain populations. Coevolution is also capable of driving negative relationships between organisms such as parasites and their hosts, although this still results in greater genetic variation. The cheater moth Tegeticula intermedia, is very closely related to the mutualistic moth T. cassandra. Although both possess similar ovipositor characteristics, the cheater moth lays its eggs directly into the fruit and does not return the favor by pollinating the host plant (Segraves 2004). Researchers have also attempted to test at what point the mutualism reverts to an antagonistic relationship which unfairly favors one species over the other. Segraves et al. test the evolutionary ecology of these cheater moths and how they were able to exploit the mutualism. Their testing required years of rearing populations of two mutualist moth species, T. cassandra and T. yucasella, with varying ovipositor morphology. The results showed that even though T. cassandra had ovipositor similar to cheater populations the emergences of cheater moths in the test populations were extremely small. The results also indicated that ovipositor morphology was important in producing cheater individuals as T. yucasella moths which had smaller and narrower ovipositors were less likely to cheat as they could not penetrate the fruit. At least in the Tegeticula genus of yucca moths the rate of cheating is incredibly low, and this was proven even in synthetic evolutionary conditions (Segraves 2008). This suggests that there are biological checks in play inhibiting great numbers of cheater moths from emerging, as this would result in an evolutionarily unstable paradigm.

Another research study was conducted on cheating, but this time scientists chose to study the T. intermedia more directly, and study mtDNA sequences and create a phylogenetic tree to infer where these cheater moths have originated from. The team utilized Amplified Length Polymorphism techniques to examine the DNA sequences into a proper phylogenetic relationship. The maximum-likelihood analysis resulted in a single tree which adequately showed the relationships between the cheater moth T. intermedia and T. cassandra. Phylogeographical contexts are also explored here, as results disproved that T. intermedia branched out of Florida; instead the cheater species most likely evolved in western North America, and subsequently spread eastward. The sequencing data reflects this incidence of migration as T. intermedia of western regions possess far greater genetic diversity than those of eastern regions. This effectively means that Prodoxidae populations originally diverged years ago, splitting into the east and west; where cheater populations only emerged in the west (Segraves 2004). It would appear that cheating populations have survived for a long time and even though their reemergence is low, an explanation was needed as to how they were maintained in the population. The answer is that cheating populations and their mutualistic variants for the same host plant are never sister taxa. Sympatric evolution of cheaters is inherently unstable and does not occur, however, cheater populations are free to move and attempt to take advantage of host plants of other more distantly related members of the Prodoxidae. This is supported by phylogenetic evidence which suggests that host choice among cheaters and mutualists are paraphyletic and evolved separately (Pellmyr 1997). To analyze these circumstances further scientists studied cheating in the Yucca plants. Cheating in the plants of Yucca species are even rarer than Prodoxidae cheaters, but there occurrence is never the less related. Cheater plants such as those seen in Y. baccata deny their pollinators to access to their seeds and prevent larvae from growing. Reduced occurrence of Y. baccata indicates that cheater plants occur in a frequency-dependent fitness character with cheater moths, but do not evolve by themselves as this would be evolutionarily unstable. Cheater yucca plants are substantially less successful than their cheater moth counterparts and so usually only seen very rarely and are completely absent from many Yucca plant species (Crabb 2004).

In an effort to understand the role of interaction type on the phylogenetic structure of the Yucca moths, researchers performed a test by utilizing non-mutualistic moths and a mutualistic species of Yucca moth in combination with a single Yucca plant. The mutualistic Yucca moths showed the highest rates of diversification. Interaction type also affects population size and gene flow. The location of where moths are able to feed in the testing demonstrates either an ability to easily migrate into different locations, or stopped this entirely (Althoff 2007). In conclusion there is expansive evidence that coevolution has played and large role in the development of mutualists in the Yucca genus and Prodoxidae family of moths. By capturing of Yucca moths from a vast array geographical areas, reliable phylogenetic evidence was pieced together, which helped prove the importance of coevolution in the context of mutualism between hosts and moths. There is also a seemingly harsh threat to the balance of mutualism with interference from cheater populations; however, these cheater populations have extremely low emergence rates and not high enough gene flow to offset the mutualism of moths and hosts in mutualism. Yucca moths have benefitted tremendously by allowing their larvae to grow in the Yucca plant where it is protected and has access to nutrients; this is also true of the plants who have access to specialized pollinators. Although there is evidence that suggests certain compatible traits were pre-adapted, coevolution has been a strengthening evolutionary force for organisms adapted to mutualistic behaviors. Coevolution gave rise to better ovipositor length and stability, tentacular appendages capable of transplanting pollen more effectively and specialized pollinator behavior. Coevolution resulted from and allowed for the higher fitness of moths and plants that were better able to succeed by helping each other.

References

Althoff, D. M., Svensson, G. P., & Pellmyr, O. May 01, 2007. The influence of interaction type and feeding location on the phylogeographic structure of the yucca moth community associated with Hesperoyucca whipplei. Molecular Phylogenetics and Evolution, 43, 2, 398-406.

Crabb, Beau Amadeus, and Olle Pellmyr. 2004. Defection by plants in the yucca–yucca moth association: a test of the cheater plant hypothesis for Yucca treculeana. Oikos 107, no. 2: 321-328.

Groman, Pellmyr, and Joshua D. Groman. 2000. Rapid evolution and specialization following host colonization in a yucca moth. Journal Of Evolutionary Biology 13, no. 2: 223-236.

Godsoe, W., Yoder, J. B., Smith, C. I., & Pellmyr, O. January 01, 2008. Coevolution and divergence in the Joshua tree/yucca moth mutualism. The American Naturalist, 171, 6, 816-23.

Pellmyr, Olle, and John N. Thompson. 1996. Evolution of pollination and mutualism in the yucca moth lineage. American Naturalist 148, no. 5: 827.

Pellmyr, O. M., J. C, Huth. 1997. Non-mutualist yucca moths and their evolutionary consequences. Nature, 380, 155–156.

Segraves, K.A. & Pellmyr, O. 2004. Testing the out-of-Florida hypothesis on the origin of cheating in the yucca–yucca moth mutualism. Evolution, 58, 2266–2279. Segraves, K. A., Althoff, D. M., & Pellmyr, O. 2008. The evolutionary ecology of cheating: does superficial oviposition facilitate the evolution of a cheater yucca moth?. Ecological Entomology, 33(6), 765-770.

Yoder, Jeremy B., Smith, Christopher, I., & Pellmyr, O. August 01, 2010. How to become a yucca moth: minimal trait evolution needed to establish the obligate pollination mutualism. Biological Journal of the Linnean Society, 100, 4, 847-855.

EEOB 3310 – Evolution Thursday, 9:10; David Salazar-Valenzuela Wikipedia Topic - Talk and Edit pages

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

Edited on Talk Page - I believe that article could include more about the mutualism and co-evolution between Yucca moths and the Yucca plant. The article does not include facts about possible antagonistic relationships of cheater Yucca moths. Cheater Yucca moths have appeared in certain populations and species of Yucca plants and do not assist the plants in pollination efforts, instead the moths only take advantage of the plants. The article does not address biogeography in the diversification of Yucca plant species. Biogeography has played a vital role in the survival of Yucca plants, and thus also affected the evolution of mutualistic Yucca moth species. The article can also explain the needs of Yucca plants vs. those of their mutualistic moths. Moth species that have relied on Yucca plants for laying eggs, diversified more rapidly than non-mutualistic moths.

Edited on Page - Although certain species of the Yucca moth have evolved antagonistic features against the plant and do not assist in the plants pollination efforts while continuing to lay their eggs in the plant for protection.

EEOB 3310 – Evolution Thursday, 9:10; David Salazar-Valenzuela Wikipedia Topic - Annotated Bibliography

Topic: The coevolution and spanning mutualism between Yucca plants and the Yucca moths. Has it always stayed mutual, was coevolution the sole major force of evolutionary change in these organisms?

Godsoe, W., Yoder, J. B., Smith, C. I., & Pellmyr, O. (January 01, 2008). Coevolution and divergence in the Joshua tree/yucca moth mutualism. The American Naturalist, 171, 6, 816-23.

This source explains that coevolution is what drives change and diversification in the Yucca moth and the Joshua tree more commonly known as the Yucca palm. The researchers tested this hypothesis by setting up a differential selection of two species of yucca moths and two corresponding species of Yucca palms which they pollinate. The study showed floral traits involving pollination evolved substantially more rapidly than other flower features. The study then looks at phylogeny and determines that coevolution is the major evolutionary force behind diversification in the Yucca moths and Yucca palms. The article answers the basis of my topic question, and helps set the ground work for more information regarding other Yucca moth and plant mutualisms.

Yoder, Jeremy B., Smith, Christopher, I., & Pellmyr, O. (August 01, 2010). How to become a yucca moth: minimal trait evolution needed to establish the obligate pollination mutualism. Biological Journal of the Linnean Society, 100, 4, 847-855.

The source examines the origins behind pollination mutualisms and looks into the Yucca moth and plant mutualism as primary examples. The researchers attempt to find an answer as to how integral coevolution was as the driving force behind various adaptions between the Yucca moth and plant species. The researchers used phylogenetic examination to reconstruct the trait evolution of the pollinating Yucca moths and their non-mutualistic variants. The article suggests that certain mutualistic traits have predated the Yucca moth-plant mutualism, such as larval feeding in the floral ovary, however, it suggests that other key traits linked to pollination were indeed a result of coevolution between the two species. The source plays a powerful role in for my topic by attempting to differentiate other forms of evolution and traits that formed as a result of coevolution.

Segraves, K. A., Althoff, D. M., & Pellmyr, O. (2008). The evolutionary ecology of cheating: does superficial oviposition facilitate the evolution of a cheater yucca moth?. Ecological Entomology, 33(6), 765-770. doi:10.1111/j.1365-2311.2008.01031.x

This article looks at the Yucca mutualism and attempts to understand at what point the mutualism reverts to an antagonistic relationship which unfairly favors one species over the other. The researchers explain that cheater moths have come to be and actively take advantage of Yucca plants. They test the evolutionary ecology of these “cheater moths” and how they were able to exploit the mutualism. The paper concludes that certain characteristics such as being able to lay eggs directly into fruit of the Yucca plant propel cheater species, however, cheater populations are incredibly rare and thus it does not happen frequently in this mutualism. This paper is integral in answering the portion of the topic expanding on evolution of an antagonistic relationship from a mutual one.

Segraves, K. A., & Pellmyr, O. (May 01, 2001). Phylogeography of the yucca moth Tegeticula maculata: the role of historical biogeography in reconciling high genetic structure with limited speciation. Molecular Ecology, 10, 5, 1247-1253.

This article looks at the connection between biogeography and phylogeny and attempts to understand what role did location of the moths play in the evolution of their traits. It compares the Tegeticula m. moth with sister species that have gone a substantially higher degree of diversification and evolution. The researchers looked at many kinds of phylogenetic data including mitochondrial DNA of the species. The study concluded by demonstrating that rate of evolution in this species relates to Yucca plant mutualism and includes that in certain parts the plant has not been very successful which in turn limits evolutionary potential of pollinating moths. This article is necessary for my paper due to the information which it uncovers about forces other than coevolution, such as biogeography responsible for evolution. It also highlights the importance of mutualism in later stages of evolution in the species of moths.

Althoff, D. M., Svensson, G. P., & Pellmyr, O. (May 01, 2007). The influence of interaction type and feeding location on the phylogeographic structure of the yucca moth community associated with Hesperoyucca whipplei. Molecular Phylogenetics and Evolution, 43, 2, 398-406.

This article attempts to understand the role of interaction type on the phylogenetic structure of the Yucca moths. The researchers tested this by utilizing non-mutualistic moths and a mutualistic species of Yucca moth in combination with a single Yucca plant. Through this test, they found that mutualistic Yucca moths showed the highest rates of diversification. In conclusion, the article notes that interaction type plays important roles in population size and gene flow. This paper shows the degree to which mutualism plays a role in evolutionary patterns between plant and moth. This should be useful in explaining differences and highlighting advantages of mutualistic Yucca moths when it comes to evolution.