The Integration of Invasive Species into Marine Ecosystemss
This section of the book deals largely with what happens once invasive species have become established, whereas the previous two sections dealt primarily with how the arrival and establishment of these species occurs. Invader interactions can take many fo
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The Integration of Invasive Species into Marine Ecosystems Gil Rilov
13.1
Introduction
This section of the book deals largely with what happens once invasive species have become established, whereas the previous two sections dealt primarily with how the arrival and establishment of these species occurs. Invader interactions can take many forms and it is expected that most species would interact with their biotic and abiotic environment in more than one way. Indeed, a truly comprehensive list of the impacts of invaders would be identical to a list of the role of any species in an ecosystem. Although the kinds of interactions may not be unique between exotics and natives, what is likely to differ is the degree to which effects occur, due to such factors as differing evolutionary histories and disruptions to habitats or species that may be concomitant with invasions. It is these ecological interactions that lie at the heart of the concern about invasive species. In a recent cover-page article in NEWSWEEK (January 15, 2007) it was estimated that globally bioinvasion toll (terrestrial and aquatic combined, including pests and pathogens) on the economy and the environment is close to US$1.4 trillion a year, and will only increase!
13.2
Are Most Marine Invasions Ecologically Harmless?
Despite all this, out of the thousands of introduced marine species, we only hear of relatively few that have caused notable impacts on their new environment. Why is that? Is it because most of them are harmless? Is it because we have not measured or monitored their effects properly or persistently? Or is it because most of them are recent invaders, and given enough time many will become harmful? Furthermore, as Carlton suggests in Chap. 2, it is possible that many early invasions of species that are now thought to be indigenous (in specific regions) or cosmopolitan have actually caused considerable alteration to native communities but we just don’t know about it because nobody recorded that change.
G. Rilov, J.A. Crooks (eds.) Biological Invasions in Marine Ecosystems. Ecological Studies 204, © Springer-Verlag Berlin Heidelberg 2009
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G. Rilov
The question of whether most invaders are ecologically harmless touches on a very basic ecological topic: does the existence or well-being of one species always come at the expense, however minute, of some other species in the same habitat? The honest answer to this question is that we don’t really know because nature is very complex and we cannot measure everything. For example, in the case of possible competition, we cannot measure all the resources that a particular species is using and may be competed for by an invader. In reality, we might expect the full range of effects from huge to minute, and sometimes the effect of an invader can in fact be “positive”, in terms of increasing the fitness of a native species. Ecosystem engineers (Chap. 16, Crooks), for instance, can facilitate the proliferation of both native and invasive species by supplying a suitable habitat. Is facilitati
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