Thursday, March 11, 2010

Predator-prey interactions and evolution

To what extent have predator-prey interactions facilitated evolution? Be able to give an example of an interaction in real life.
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5 comments:

  1. Andrew JiMarch 12, 2010 at 4:09 PM

    I believe that predator-prey interactions affects evolution through the development of defense mechanisms for prey and efficient capture mechanisms for predators. For example, on page 121 the Asian giant hornet with its jaws, stinger, and wings are extremely efficient killing machine for its own survival and for food for their offspring. The prey is usually honeybees for the food that the honeybees have stored; however, because these honeybees have dealt with hornets before, the honeybees are able to call together a large group of worker bees and literally surround and roast the hornet entering the honeybee's home. Honeybees require the vibrating abdomens to be able to increase the temperature inside the ball honeybees to fry the predator. However, predator-prey interactions are not static, with predators and prey adapting to new environments and trying to survive. I think there are many other factors relating to survival and reproduction that will also facilitate evolution.

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  2. JsandfordMarch 13, 2010 at 1:42 PM

    Andrew's right, defensive and offensive mechanisms definitely play a part in natural selection. Like the honeybee/wasp example, while the Asian hornet is able to easily prey on honeybees with all of the developed traits the wasp has, some honeybees have a defense mechanism that wards away predators. In addition to defense and offense, there's also camouflage, like the oldfield mice (p. 116). These mice possibly migrated to the beaches from the mainland, where the typical brown coats of the mainland mice helped them to better evade predators such as owls, hawks, and herons. However, on the beaches, where the sand is a lighter colour, the experiments done by Donald Kaufman at Kansas State showed that the predators were more likely to eat the mice that had a darker coat, and so stood out more on the lighter beaches. Over time, the darker mice were eaten, (and so could not reproduce) so the lighter coloured mice flourished. Eventually, the population of oldfield mice became lighter coloured than their mainland cousins. Therefore, continuing with Andrew's thoughts that "predator-prey interactions are not static," a factor that can affect predator-prey interactions is the environment. There are of course many other factors, as well.

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  3. Samantha PMarch 14, 2010 at 11:04 AM

    Andrew and Jolyn’s posts gave are great examples of how the evolution of prey is facilitated by selective advantages that help protect against predators. I’d like to point out that this can also work in the opposite way; the predators can evolve such that the predator is more able to capture prey (and thus have more energy to survive and reproduce!). On pg. 102-103, Coyne discusses different species of Hawaiian finches. The birds are very similar except for their different beak shapes (Figure 22). One species has a slender bill so that it can drink nectar from tubular flowers; one species has a sharp large bill so that it can cut through bark and twigs to find beetle larvae; another species has a short strong bill to open seed pods to access seeds. Clearly all these species of finches evolved from a common ancestor to occupy different niches, and better find prey. By having a large sharp bill, the unique finch had the selective advantage of being able to obtain energy from prey found in bark and twigs. The evolution of finch beaks in this case is dependent on the assortment of prey available. The different types of prey present on the island is what allowed the finches to evolve into distinct species.
    In addition, this idea exemplifies the link between structure and function. The unique structures of the various beaks are idea for their respective functions. A long slender beak is ideal for the function of extracting nectar from tubular flowers. Without this specific structure of the beak, the bird would be unable to obtain the nectar without damaging the flower.

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  4. RadheApril 2, 2010 at 11:32 AM

    To Sam’s point, I think she’s right in saying we should take a step back and look at the other side of predator-prey interactions also. In fact, one could argue that predator evolution has been facilitated more than prey evolution by predator-prey interactions. According to Coyne, “it is reproduction, not survival, that determines which genes make it to the next generation and cause evolution,” (120) and as Andrew and Jolyn pointed out, predator-prey interactions have mainly caused the evolution of defense mechanisms in prey, adaptations that focus more on survival when encountering a predator. Given, these adaptations indirectly help reproductive success because if the prey can survive, it is more likely to reproduce; however, for predators, it takes less energy to hunt then to defend, so the extra energy that predators have increases the chance for reproductive success. (http://www.sciencedaily.com/releases/2009/07/090722142830.htm)

    An example of predator-prey interactions facilitating predator evolution can be seen in the soap-berry bug Coyne discusses in chapter five. This organism has a long, needlelike beak to penetrate the fruits of plants like the soapberry bush and consume the seeds inside. (Coyne 134) New plants were introduced into its range, two that had larger fruits than the soapberry bush. The soap-berry bug evolved as natural selection favored bugs with larger beaks that were able to penetrate the larger fruit and reach the seeds (135).

    Like Sam’s example, this also relates to the relationship between structure and function, because larger beaks were able to perform the function of getting to the seeds in the larger fruits of these new, introduced species. Additionally, this relates to energy transfer because since the bugs were able to adapt, these organisms could use the new plants as a food source, which is continuous with the idea that energy flows from producers to consumers in an ecosystem (Campbell 6).

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  5. AnonymousApril 14, 2010 at 11:07 PM

    Predator-prey interactions are perhaps the strongest driving force behind evolution. In predator prey relationships, prey develop adaptations that allow them to escape from the predator. However, as Sam and Radhe stated earlier, predators can develop adaptations to allow them to hunt their prey more effeciently. The specificity of these adaptations is amazing. As Andrew mentioned previously, and Jolyn explained, the native Japanese honeybees developed a defense mechanism against the powerful Asian hornet: the honeybees would surround the wasp and vibrate their abdomens, essentially roasting the hornet alive while the honeybees escaped unscathed. In this case, the Japanese honeybee developed an incredibly specific defense mechanism for a specific predator.
    The bat is a very innovative predator. Having very poor sight, the bat would have no advantage hunting prey at night. Therefore, bats are nocturnal, sleeping during the day and then hunting during the night. And as for finding prey in the dark, bats use a technique called echolocation, in which they bounce sound waves off of objects to create an image of their surroundings. This allows bats to 'see' perfectly in the dark, while their prey can't really see. However, some prey have developed their own way to avoid being eaten by the bats. "Some moths are able to detect incoming sonar and take evasive action" (Source 1). Moths have evolved to be able to detect sonar coming from bats. Even though the moths can't necessarily see in the dark, they can tell when bats are sending out sonar. The moths take this as a sign that the bats are out hunting, and take evasive maneuvers to avoid being the bat's next meal.
    Campbell defines a fixed action pattern as "A type of behavior directly linked to a simple stimulus" (Campbell 1121). In the case of moths and bats, the sonar that the moths detect can be thought of as a stimulus. The moth interprets this stimulus, the sonar, and then a fixed action pattern is triggered, where the moth performs evasive maneuvers to escape the bat.
    The course outline book defines evolution in organismal biology as "when a population's local environment changes unfavorably, the population adapts, migrates, or dies" (COB). This is essentially the main theme behind predator-prey evolution. Certain environmental changes, such as predators, place stress on prey. Prey must develop adaptations or they will die to their predators. Predators must then develop adaptations or they will starve and die themselves.
    Sources: http://www.globalchange.umich.edu/globalchange1/current/lectures/predation/predation.html
    Campbell

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