Tuesday, March 9, 2010
Island Biography
In Chapter 4 "Geography of Life," Coyne explains how the species present on islands are direct evidence that evolution has occurred. Coyne describes how evolution has caused the unique species make up of islands to form. Now, connect Coyne's observations to the theory of island biodiversity studied in the ecology unit. Why do certain types of islands seem to consistently host more species than others? It maybe helpful to discuss the size of the island, distance of island from mainland, extinction rates and migration rates in your explanation. Furthermore, discuss a current problem that threatens island biodiversity today, the importance of island biodiversity to our society and/or a possible solution to help save island biodiversity.
Subscribe to:
Post Comments (Atom)
In the island equilibrium model, islands that are larger and closer to the mainland are more likely to have a greater number of different species; it is more probable that an organism will land on an island with a greater area, or one that is nearer to the mainland, resulting in a higher immigration rate (Campbell 1217). In addition, larger islands typically have a lower extinction rate, since they can support more diverse habitats.
ReplyDeleteAnother factor that could be included by Campbell is the origin of the island. In chapter 4, Coyne explains that continental islands, which were once a part of the mainland, have a greater biodiversity than oceanic, or volcanic-formed islands (Coyne 100). This is because oceanic islands begin as virtually lifeless areas, and therefore are populated through primary succession (Campbell 1212). As a result, the only species that can populate an oceanic island are ones that can travel over water, such as birds, bats, insects, and plants. In addition, many of these species evolve to fill ecological niches, such as the Galápagos finches that vary in beak shape to access different food (Coyne 102).
In the last couple of centuries, some species have invaded islands through human intervention, either accidentally (rats, snakes, etc.) or on purpose (such as the poisonous cane toad introduced in Hawaii to control beetles (Coyne 101)). The result of these invasions can be devastating, since the native species on the islands are not adapted to dealing with the introduced predators. For example, the brown tree snake, accidentally introduced in Guam in the 1950’s, has caused the extinction of 12 species of birds and 6 species of lizards (Campbell 1249).
One way to save island biodiversity is through customs checks, which would prevent nonnative species from being introduced to an island. Also, more regulation could prevent humans from purposefully introducing nonnative species to control native “pests.” It is important to preserve island biodiversity, since most of the organisms are dependent on one another for survival.
This comment has been removed by the author.
ReplyDeleteI agree with Jaime on how the size of the island and the distance the island is from land both contribute to the species diversity of that island. If an island is very diverse, then it is most likely close to land and very large. The species diversity of the island is dependent on the number of species that migrate to the island.
ReplyDeleteElaborating what Jaime said, the closer the island, the more immigrants will land there. The bigger the island, the more immigrants will land there. However, I would also like to add that if an island is big, there is a lower rate of extinction than an island that is small. Likewise, if an island is near, then there is lower rate of extinction than a farther island because there is a higher rate of immigration (Campbell 1616-7).
Summary of Islands:
Distance
• Close: More immigrants + less rate of extinction = More species diversity
• Far: Less immigrants + higher rate of extinction = Less species diversity
Size:
• Small: Less immigrants + higher rate of extinction = Less species diversity
• Large: More immigrants + lower rate of immigration = More species diversity
I believe the root of many island diversity problems lies within human exploitation itself. To fully understand how to help the present, we have to be able to understand the past first – that’s the reason why history exists.
In the past, the dodo bird, an undisturbed flightless bird, thrived on the island of Mauritius. However, when the Portuguese came in the 16th century, they found that these 50 pound, flightless birds were perfect targets for food.
Less than two centuries later, the bird was extinct (Bagheera).
We have not learned from the stories of the past. Just like Jaime said, species diversity has been harmed by introduced species. Just like Coyne said, “[introduced species] often take over, wiping out native species… throughout the world the story is the same: humans introduce species to oceanic islands where they did not exist, and these species displace or destroy native forms” (101-2).In this case, however, the introduced species was the homo sapian itself.
There is still illegal poaching done in this world, yet governments have not taken enough action to limit these crimes. The fierce komodo dragon, found on an Indonesian island, is currently hunted today for skins and tourism. If governments in third world countries had enough money to provide for programs that prevented poaching, then humans could help sustain this planet’s species diversity.
If we lose island species diversity in the world, we lose species that could even potentially help us. Remember, relating back to the biology course, if a keystone species in an ecosystem is removed, then the ecosystem is disrupted and could potentially lose even more species. The species are interdependent on each other, and this chain of dependence could be shattered if just one is removed. Plants that could prove to be useful herbs may be lost. Snakes with venom for the medical industry may disappear. Aside from biophilia, humans have a lot to lose in the medical field if they continue eliminating different species.
Humans have a lot to lose by destroy species diversity. Yet, they have a lot to gain by preserving species diversity. It’s ironic that we are potentially killing ourselves by killing others.