Guangdong Provincial Key Laboratory of Applied Botany, and Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China.
CEFE, UMR 5175, CNRS, Univ Montpellier, Univ Paul-Valéry Montpellier, EPHE, IRD, 1919 route de Mende, F-34293, Montpellier Cédex 5, France.
BMC Evol Biol. 2018 Sep 4;18(1):134. doi: 10.1186/s12862-018-1239-5.
While the communities constituted by phytophageous insects and their parasites may represent half of all terrestrial animal species, understanding their diversification remains a major challenge. A neglected idea is that geographic phenotypic variation in a host plant may lead to heterogeneous evolutionary responses of the different members of the associated communities. This could result in diversification on a host plant by ecological speciation in some species, leading to geographic variation in community composition. In this study we investigated geographic variation of inflorescence receptacle size in a plant, Ficus hirta, and how the hymenopteran community feeding in the inflorescences has responded. Our predictions were: 1) Inflorescence size variation affects wasp species differently depending on how they access oviposition sites. 2) In some affected lineages of wasps, we may observe vicariant, parapatric species adapted to different inflorescence sizes.
We show that fig (the enclosed inflorescence of Ficus) wall thickness varies geographically. The fig-entering pollinating wasp was not affected, while the parasites ovipositing through the fig wall were. Two parapatric species of Philotrypesis, exhibiting strikingly different ovipositor lengths, were recorded. One species of Sycoscapter was also present, and it was restricted, like the shorter-ovipositor Philotrypesis, to the geographic zone where fig walls were thinner.
Previous work on fig wasps suggested that parapatric geographic ranges among congenerics were due to adaptation to variation in abiotic factors, complemented by interspecific competition. Our results show that parapatric ranges may also result from adaptation to variation in biotic factors. Within an insect community, differences among species in their response to geographic phenotypic variation of their host plant may result in geographically heterogeneous community structure. Such heterogeneity leads to heterogeneous interaction networks among sites. Our results support the hypothesis that plant geographic phenotypic variation can be a driver of diversification in associated insect communities, and can complement other diversification processes.
虽然以植物为食的昆虫及其寄生虫构成的群落可能代表了所有陆地动物物种的一半，但对它们的多样化仍然是一个主要挑战。一个被忽视的观点是，宿主植物的地理表型变异可能导致相关群落的不同成员产生不同的进化反应。这可能导致某些物种通过生态物种形成在宿主植物上多样化，从而导致群落组成的地理变化。在这项研究中，我们调查了植物榕属植物的花序托大小的地理变异，以及在花序中取食的膜翅目昆虫群落的反应。我们的预测是：1）花序大小的变化会根据黄蜂进入产卵地点的方式而对不同的物种产生不同的影响。2）在一些受影响的黄蜂谱系中，我们可能会观察到适应不同花序大小的并系、邻域物种。
我们表明，榕属植物的（封闭的花序）壁厚度存在地理变异。进入榕属植物的传粉黄蜂不受影响，而通过榕属植物壁产卵的寄生虫则受到影响。两种地理上近缘的 Philotrypesis 表现出明显不同的产卵器长度，被记录下来。还有一种 Sycoscapter 也存在，它与产卵器较短的 Philotrypesis 一样，局限于榕属植物壁较薄的地理区域。
以前对榕属黄蜂的研究表明，同属近缘种的地理分布范围近缘是由于对环境因素变化的适应，辅以种间竞争。我们的结果表明，地理分布范围也可能是由于对生物因素变化的适应。在昆虫群落中，物种对其宿主植物地理表型变异的反应差异可能导致地理上不均匀的群落结构。这种异质性导致了各地点之间的不均匀的相互作用网络。我们的结果支持这样一种假说，即植物地理表型变异可以成为相关昆虫群落多样化的驱动力，并可以补充其他多样化过程。
