Buckling Angus, Rainey Paul B
Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
Nature. 2002 Dec 5;420(6915):496-9. doi: 10.1038/nature01164.
Exploiters (parasites and predators) are thought to play a significant role in diversification, and ultimately speciation, of their hosts or prey. Exploiters may drive sympatric (within-population) diversification if there are a variety of exploiter-resistance strategies or fitness costs associated with exploiter resistance. Exploiters may also drive allopatric (between-population) diversification by creating different selection pressures and increasing the rate of random divergence. We examined the effect of a virulent viral parasite (phage) on the diversification of the bacterium Pseudomonas fluorescens in spatially structured microcosms. Here we show that in the absence of phages, bacteria rapidly diversified into spatial niche specialists with similar patterns of diversity across replicate populations. In the presence of phages, sympatric diversity was greatly reduced, as a result of phage-imposed reductions in host density decreasing competition for resources. In contrast, allopatric diversity was greatly increased as a result of phage-imposed selection for resistance, which caused populations to follow divergent evolutionary trajectories. These results show that exploiters can drive diversification between populations, but may inhibit diversification within populations by opposing diversifying selection that arises from resource competition.
剥削者（寄生虫和捕食者）被认为在其宿主或猎物的多样化以及最终的物种形成过程中发挥着重要作用。如果存在多种抗剥削者策略或与抗剥削者相关的适应性成本，剥削者可能会推动同域（种群内部）多样化。剥削者还可能通过创造不同的选择压力并提高随机分歧率来推动异域（种群之间）多样化。我们研究了一种烈性病毒寄生虫（噬菌体）对荧光假单胞菌在空间结构微观世界中多样化的影响。在此我们表明，在没有噬菌体的情况下，细菌迅速多样化为空间生态位专家，在重复种群中具有相似的多样性模式。在有噬菌体的情况下，同域多样性大大降低，这是因为噬菌体导致宿主密度降低，减少了对资源的竞争。相反，由于噬菌体对抗性的选择作用，异域多样性大大增加，这导致种群沿着不同的进化轨迹发展。这些结果表明，剥削者可以推动种群之间的多样化，但可能会通过对抗由资源竞争产生的多样化选择来抑制种群内部的多样化。
