Monday, April 28, 2008

Benefits of invading exotic organisms in a marine environment

Student post submitted by Darin Alexander.


ResearchBlogging.orgWhen we think of invading exotic species you already have a negitive view in your mind. There is a high rate of negative publicity on exotic species. They are thought to be destructive, and can cause large amounts of stress and possible extinction of native species. This is a true statement when it comes to terrestrial or aquatic species, but what about marine? In this article John Briggs discusses the benefits, yes benefits, invasive species can have on marine environments. (Continues below...)


Briggs discusses the ongoing situation taking place in the Mediterranean. Since the opening of the Suez Canal in 1869 there has been a steady stream of invading species to the Mediterranean from the red sea. 300 of these organisms are now established in the area. The organisms documented are 59 fish species, 129 mollusk species and 49 crustacean species. You would think with all these new entering species they must be pushing out native ones. This is a surprisingly wrong assumption. From the data collected there have been no extinctions due to the newly invading species. They have actually increases the community’s biodiversity and has been beneficial. Introduced primary consumers have increased consumption of producers and allowed more access to energy. This helps increase the community’s productivity. People commonly lump the problem of aquatic and terrestrial invaded species with marine but this is a mistake.


It has been shown that there is no obvious detrimental effect invading species have on marine environment. In most instances marine invaders are needed to help keep up the populations biodiversity. This article also talks about the migration of mollusks 5.4 billion years ago across the Bering Strait. The mollusks came from the pacific region of the U.S and settled on the coast of Europe and Eastern America. A statistic given is now 47% of the original pacific species established on the east coast has diverged into a separate species. This is Evolution and species divergence at hand. Also with fossil records they were able to prove that the invading species caused no extinction of the original native species and in some cases the populations assimilated together.


This was a very interesting article and it shows different aspects of things we have leaned in class this year. We go from migration, to competition, to nitch differentiation, to species divergence, then to assimilation and eventually evolution. It also sheds some light on the benefits of exotic organism invasion and shows us that it is not always bad.


Reference:


Briggs, J.C. (2007). Marine biogeography and ecology: invasions and introductions. Journal of Biogeography, 34(2), 193-198. DOI: 10.1111/j.1365-2699.2006.01632.x


Abstract:


Although biogeography and ecology had previously been considered distinct disciplines, this outlook began to change in the early 1990s. Several people expressed interest in creating a link that would help ecologists become more aware of external influences on communities and help biogeography’s realize that distribution patterns had their genesis at the community level. They proposed an interdisciplinary approach called macroecology. This concept has been aided by the advent of phylogeography, for a better knowledge of genetic relationships has had great interdisciplinary value. Two areas of research that should obviously benefit from a macroecological approach are: (1) the question of local vs. regional diversity and (2) the question of whether invader species pose a threat to biodiversity. The two questions are related, because both deal with the vulnerability of ecosystems to penetration by invading species. Biogeographers, who have studied the broad oceanic patterns of dispersal and colonization, tend to regard isolated communities as being open to invasion from areas with greater biodiversity. It became evident that many wide-ranging species were produced in centres of origin, and that the location of communities with respect to such centres had a direct effect on the level of species diversity. Ecologists, in earlier years, thought that a community could become saturated with species and would thereafter be self-sustaining. But recent research has shown that saturation is probably never achieved and that the assembly of communities and their maintenance is more or less dependent on the invasion of species from elsewhere. The study of invasions that take place in coastal areas, usually the result of ship traffic and/or aquaculture imports, has special importance due to numerous opinions expressed by scientists and policy-makers that such invasions are a major threat to biodiversity. However, none of the studies so far conducted has identified the extinction of a single, native marine species due to the influence of an exotic invader. Furthermore, fossil evidence of historical invasions does not indicate that invasive species have caused native extinctions or reductions in biodiversity.



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