Science2014-06-10 3:21 PM

竹节虫研究确定进化的某些方面既能预测也可重复 Stick Insect Genomes Reveal Natural Selection’s Role in Parallel Speciation

论文摘要 

通过将竹节虫从它们最喜欢的植物宿主移植到替代宿主并观察其基因组会发生什么情况,研究人员已经确定,进化的某些方面既能预测也可重复。

Víctor Soria-Carrasco及其同事对Timema cristinae竹节虫进行了研究,这种竹节虫在美国加利福尼亚州为适应不同环境条件已经演变出了2种生态型——或物种的不同变体
他们首先对这些生态型的基因组进行了测序——这些生态型的竹节虫已经适应于植物Adenostoma fasciculatum或是植物Ceanothus spinosus——并将它们进行比较以观察这些生态型的环境是如何影响其基因组的。

研究人员在竹节虫的生态型中发现了数千个分化的基因组区域,它们中有许多涉及蛋白编码基因,但他们注意到这些基因组变化的大多数是由地理位置而非宿主植物所驱动的。他们说,即使这样,各种竹节虫生态型在类似的基因组区域会共有比由概率所预计的更多的突变。

因此,Soria-CarrASCo及他的同事将其不同生态型的竹节虫进行移植——即将它们转移到不同的宿主植物并发现,这些不同生态型的竹节虫只在其被转移到不同宿主植物的一个世代后,其基因组就会显示出汇聚及分化区域。

总之,这些结果提示,自然选择可以在某物种的不同生态型中通过诱导它们中的平行基因改变而驱动一种平行演化。他们还提出,这种会复制的物种可在类似的环境压力下分别演化。

Abstract 

Natural selection can drive the repeated evolution of reproductive isolation, but the genomic basis of parallel speciation remains poorly understood. We analyzed whole-genome divergence between replicate pairs of stick insect populations that are adapted to different host plants and undergoing parallel speciation. We found thousands of modest-sized genomic regions of accentuated divergence between populations, most of which are unique to individual population pairs. We also detected parallel genomic divergence across population pairs involving an excess of coding genes with specific molecular functions. Regions of parallel genomic divergence in nature exhibited exceptional allele frequency changes between hosts in a field transplant experiment. The results advance understanding of biological diversification by providing convergent observational and experimental evidence for selection’s role in driving repeatable genomic divergence.

Editor's Summary

Stick to the Bush

Can the underlying genetic changes driving the divergence of populations into new species be predicted or repeated? Soria-Carrasco et al. (p. 738) investigated the genetic changes observed after one generation when stick insect (Timema cristinae) populations were transplanted from their preferred host plants to alternative hosts. Diverged genetic regions were relatively small, with most loci showing divergence in a single population pair. However, the number of loci showing parallel divergence was greater than expected by chance. Thus, selection can drive parallel phenotypic evolution via parallel genetic changes.

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