Science2014-06-11 2:25 PM

尽管食物选择少,但物种数丰富 Lethal Interactions Between Parasites and Prey Increase Niche Diversity in a Tropical Community

论文摘要 

研究人员对热带蝇类以及在其体内产卵的寄生蜂进行了仔细观察后揭示出了一个难以置信的相互作用的复杂网络,如果没有先进的分子技术,其中的一些相互作用仍然不会被发现。该复杂网络提出了有关物种是如何相互作用的问题。要揭示物种间相互作用的结果是富有挑战性的。

例如,物种往往会占据一种被称作生态位的生态空间,在该生态位中含有它们生存及繁殖所需的资源,而它又进一步地受到物种与掠食者和竞争者相互作用的界定限制。此外,物种往往会在特定的生态位中特化,并因而减少物种间对资源的竞争。这种区分被认为与物种多样性的产生有关,因为物种会在其适应于不同生态位时进行分化。

这些系统,特别是那些位于热带的系统,似乎包含有比一个人能够简单地根据对生态位的估计数所计算的物种要更多。了解帮助定义某生态位的物种(包括掠食者和竞争者)间的相互作用会因为那些难以被观察到的物种而变得尤其具有挑战性。

应用新的分子技术,科学家们已经在了解吃植物的昆虫群体及在它们体内产卵的寄生蜂群体是如何相互作用以在某单一种类寄主植物内建立独特的生态位并因而产生高度多样化等方面取得了进展。(寄生蜂会影响所有吃植物昆虫中的大多数,并在它们的寄主体内产卵。)

在秘鲁的一个地方,Marty Condon等人对数千种吃植物的昆虫进行了研究,这些昆虫的幼虫所吃的是攀援番瓜花的多汁部分。应用分子方法来揭露有多少蝇类及寄生蜂物种存在于这个特别的地方以及它们是如何相互作用的(包括在寄生蜂产卵之前及之后),Condon及其同事发现了极端的多样性:14个蝇类物种及18个寄生蜂物种,它们都只占据了2种攀援性番瓜。

通过观察蝇类幼虫在寄生蜂产卵前的样本,科学家们发现,某些寄生蜂没有活下来,从而提示如果是在错误的蝇类物种中产卵,这些寄生蜂的后代就会死亡。因此,死亡的相互作用——在某些物种中是由寄生蜂所驱动的(杀灭蝇类),而在另外一些物种中则是由其同类,即母体寄生蜂所导致的——产生了极大数量的独特、高度界定的生态位,后者在一个简单的植物系统(其当从外部看时似乎只是某单一的资源)中让大数目蝇类和寄生蜂出现了极端的特化并让它们共存。一则《观点栏目》提供了更多的见解。


Abstract 
Ecological specialization should minimize niche overlap, yet herbivorous neotropical flies (Blepharoneura) and their lethal parasitic wasps (parasitoids) exhibit both extreme specialization and apparent niche overlap in host plants. From just two plant species at one site in Peru, we collected 3636 flowers yielding 1478 fly pupae representing 14 Blepharoneura fly species, 18 parasitoid species (14 Bellopius species), and parasitoid-host associations, all discovered through analysis of molecular data. Multiple sympatric species specialize on the same sex flowers of the same fly host-plant species—which suggests extreme niche overlap; however, niche partitioning was exposed by interactions between wasps and flies. Most Bellopius species emerged as adults from only one fly species, yet evidence from pupae (preadult emergence samples) show that most Bellopiusalso attacked additional fly species but never emerged as adults from those flies.

Editor's Summary

Hidden Diversity

Why are there so many species in the tropics? Niche partitioning by highly specialized plant species seems to be the main generator of high diversity. Condon et al. (p. 1240; see the Perspective by Godfray) show that niche partitioning can also be generated by interactions between plant resources and parasites, resulting in hyperdiverse communities. The cryptic diversity of 14 neotropical fly pollinators and 18 of their highly specific wasp parasites induced mortality partitions between multiple narrow niches. The extreme specificity of the wasp-fly relationships was initially only revealed by molecular analysis.

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