Wednesday, April 14, 2010

Native groups to oceanic islands

On page 104, Coyne has a chart of native groups in oceanic islands and groups that are usually missing. Plants, birds, and insects are in the native group and land mammals, reptiles, amphibians and freshwater fish are in the missing category. Coyne explains that this is because the native species can colonize the oceanic island trhough long-distance dispersal. What are some examples of species that have been found on oceanic islands that would fit into the missing group? How did they get there? How are they able to sustain their population?


  1. One specie that fits into the missing group is the existence of reptiles on oceanic islands. One concrete example of this is the existance of turtles. Turtles have acquired the ability to swim in oceans. Thus, they find a way to colonize in the oceanic islands. They leave their offsprings in the sandy beaches of the islands, or even the main lands. Then the offspring must crawl across the beaches into the ocean after their birth. Therefore, one of the adaptation to traveling to oceanic islands are the existance of oceanic traveling. However, another way of dispersal to oceanic islands despite their ability to process long-distance dispersal is the geological breakoff of islands from the mainland. In the island of Madagascar, there are many primitive of the primates, especially the lemurs. These lemurs do not have an ability to perform oceanic long-distance dispersal. The reason they are there is because they were in that area of land when the island broke apart from the mainland. One of the reasons why they can sustain their population is because the island provides them with enough resources and territory to colonize. Also there are enough populations there to start the colony. For example, if the lemurs' population did not satisfy the minimum viable population, then the specie of lemurs should not survive and sustain life on the oceanic islands.

    Why Evolution is True by Jerry A. Coyne

    Campbell 8eth AP Biology text book

  2. At the very beginning of that chapter, Coyne talks about Selkirk, who was basically the real-world Robinson Crusoe. He was marooned on an island (intentionally), and he lived there for 4.5 years, until he was rescued. One of the creatures that he noticed on that island were goats. Goats are generally not found on oceanic islands because they cannot swim across an entire ocean. However, goats were found on Mas a Tierra Island they "introduced by earlier sailors" (Coyne, P. 87). Since it does not specifically state how many animals were originally brought by the sailors, I assume that there were enough for the goats to reproduce and proliferate when isolated from any other goat populations.
    Another reason that the goats were able to sustain their population is because they arrived to a relatively desolate place. Other than a few displaced organisms, the goats were in a virtually perfect environment, full of food and free of predators. There may have been some competition, but obviously not much because the goats did just fine. This relates to how whales transitioned back into the ocean--they discovered a totally perfect environment and colonized an ecological niche that involved little competition and predators, similar to the goats on Robinson Crusoe Island (minus the transitioning part). This all relates back to the idea that natural selection will select traits that will increase the survival and reproductive output (Coyne, P. 120) of an organism. If it is already suited for the environment (much like the goats on Robinson Crusoe Island), then those traits will be proliferated and expressed even more so, maximizing the individual organism's fitness (1).


  3. Long distance dispersal occurs when species travel across vast bodies of waters to colonize isolated regions. Only certain species with particular adaptations are capable of doing this. These species include specific birds, insects, and various plants. It cannot occur with just any of these species; the birds and insects must be able to fly very long distances and the plants must have relatively light seeds to be carried by wind. Long distance dispersal is a selective advantage because it allows species to reach uninhabited areas with a plethora of resources. On the contrary, long distance dispersal is not advantageous because living with relatively few other life forms may mean less chance for interdependence in nature. Mutualistic relationships, such as micorrhizae between fungi and plants, are very often beneficial and increase the likelihood of survival and reproduction.

    There are several species known to have migrated due to long distance dispersal. For example, barringtonia (Lecythidaceae) is a type of Indo-Pacific Florida that reached Madagascar by long distance dispersal. Another plant species, Stronglyodon, inhabits both Hawaii and Tahiti due to long distance dispersal.

    Long distance dispersal is rare due to the methods of its execution. Natural factors move flora over long distance, such as wind and oceanic current. However, these factors have to move seedlings so far and without death that the likelihood is nearly impossible. Man can also manipulate long distance dispersal whether it be intentional or not. For instance, organisms can be carried to other countries by unknowingly by tourists. In addition, man could intentionally bring species to other lands for various purposes. This occurred in the 1400s when Columbus discovered corn in the Americas and brought it back to Europe. Long distance dispersal is not very sustainable. Species are introduced to starkly different surroundings and must adapt to them quickly. Evolution is a very slow process, making survival of these organisms unlikely. However, when long distance dispersal does occur, it is significant because it adds greater diversity to an area thus furthering evolutionary processes.


  4. Well Corey, lets first define oceanic island and compare them to continental islands. On page 100, Coyne explains that oceanic islands were never connected to a continent in any way shape or form, but rather, they "grew" out of the seafloor. I know, its weird. An inanimate land mass growing? Sounds like witchcraft to me, but its true. These islands usually rise from underwater volcanoes that eventually break the surface of the water. These contrast to continental islands (that Coyne also defines on page 100), which are islands that were connected to a continent at one point in time, but later broke from the continent.

    The significance of this difference is that is determines what sort of organism are able to physically reach these places. Continental islands were once open to land bound animals and organisms, therefore they are home to organisms suchas land mammals, reptiles,amphibians, freshwater fish, as well as plants, birds, and insects. They could crawl, walk, or run to the island, then remain there after the divorcing of the continental island from its continental spouse. Oceanic islands rise from the ocean floor relatively lifeless and are only open to organisms with long range dispersal methods like plants and birds. The likelihood that these organisms reach this island is another story, but they will get there eventually.

    The land bound animals reach these oceanic islands mainly by means of human intervention. I know, this is just another example of humans messing with the laws of evolution and nature. And that is 100% true. Humans have always been changing evolution (we may be done evolving, we have intentionally evolved different species of dog/livestock, and now we are changing what organisms go where). This is called introduction and we learned about it earlier this year. Humans bring in foreign organisms that provide us with a certain benefit so that we can have it in that new place. One example of this is in Rabbits in New Zealand. It is important to note that New Zealand is a continental island, however, rabbits were foreign and introduced by humans. Sailors brought rabbits as a source of food to these islands in the 1800s. Rabbits thrived, but eventually became a trouble to farmers. This is an example of the introduction of species to a foreign island. This is a major way in which foreign, land-bound organisms can reach oceanic islands.

    Dirty Erd
    Jerry Coyne Why evolution is true