OG13 Keystone Species那篇急求一句话的翻译，百思不得其解。。。

bobotea

这篇文章的题目还挺简单，就是里面有一句话怎么都搞不懂：
Pisaster ochraceus is often a keystone predator because it consumes and suppresses mussel populations, which in the absence of this starfish can be a dominant species.
这句话后半句实在看不懂.which应该指代mussel populations， this个人认为是指Pisaster ochracueus吧。那为什么又出来了一个主语starfish，然后连接了一个independent clause呢。搞不懂。。。好像没见过这种表达诶。向NN们请教！

bobotea

我还是把全文都贴上来吧
While the most abundant and dominant species within a particular ecosystem is often crucial in perpetuating the ecosystem, a “keystone” species, here defined as one whose effects are much larger than would be predicted from its appearance, also play a vital role.  But because complex species interactions may be involved, identifying a keystone species by removing the species and observing changes in the ecosystem is problematic.                                                               


It might seem that certain traits would clearly define a species as a keystone species; for example, Pisaster ochraceus is often a keystone predator because it consumes and suppresses mussel populations, which in the absence of this starfish can be a dominant species. But such predation on a dominant or potentially dominant species occurs in systems that do as well as in systems that do not have species that play keystone roles.  Moreover, whereas P. ochraceus occupies an unambiguous keystone role on wave-exposed rocky headlands, in more wave-sheltered habitats the impact of P. ochraceus predation is weak or nonexistent, and at certain sites sand burial is responsible for eliminating mussels.  Keystone status appears to depend on context, whether of particular geography or of such factors as community diversity (for example, a reduction in species diversity may thrust more of the remaining species into keystone roles) and length of species interaction (since newly arrived species in particular may dramatically affect ecosystem).(19)     

小熊要考G

http://forum.chasedream.com/thread-803070-1-1.html
你看下这个帖子，或许对你有帮助。

mibao93

P. ochracueus 好像就是一种海星。starfish不是主语啊，再介宾结构里不能作主语。

solitudeGG

因为po是一种海星，this starfish指的就是po