Department of Biology, University of Rochester, Rochester, NY 14627, USA.
Mol Ecol. 2010 Jan;19(2):414-25. doi: 10.1111/j.1365-294X.2009.04448.x. Epub 2009 Nov 30.
Interspecific mutualism can evolve when specific lineages of different species tend to be associated with each other from one generation to the next. Different maternally transmitted endosymbionts occurring within the same cytoplasmic lineage fulfil this requirement. Drosophila neotestacea is infected with maternally transmitted Wolbachia and Spiroplasma, which are cotransmitted at high frequency in natural populations. Molecular phylogenetic evidence indicates that both endosymbionts have been present in D. neotestacea for considerable evolutionary periods. Thus, conditions are suitable for the evolution of mutualism between them. In support of this possibility, there is a significant positive association between Wolbachia and Spiroplasma infection in many samples of D. neotestacea from natural populations. Theoretically, such a positive association can result from either mutualism between these endosymbionts or recent spread. Collections from present-day populations suggest that recent spread and mutualism have both operated to generate the positive association between Wolbachia and Spiroplasma. If selection acts on the combination of these two endosymbionts, they may be in the early stages of evolution of a more complex, cooperative association.
当不同物种的特定谱系倾向于在下一个世代彼此相关时，种间互惠共生就会进化。在同一细胞质谱系中发生的不同母系传递内共生体满足了这一要求。果蝇新亚种感染了母系传递的沃尔巴克氏体和螺原体，在自然种群中它们以高频率共同传递。分子系统发育证据表明，这两种内共生体在果蝇新亚种中存在了相当长的进化时期。因此，它们之间互惠共生的进化条件是合适的。支持这种可能性的是，在许多来自自然种群的果蝇新亚种样本中，沃尔巴克氏体和螺原体的感染之间存在显著的正相关。从理论上讲，这种正相关可能是由于这些内共生体之间的互惠共生或最近的传播所致。来自现代种群的采集表明，最近的传播和互惠共生都促成了沃尔巴克氏体和螺原体之间的正相关。如果选择作用于这两种内共生体的组合，它们可能处于更复杂的合作共生进化的早期阶段。
