关键词: 榕小蜂, 线粒体DNA, 线粒体假基因, 净化选择, 物种分化时间, 分子化石

Abstract:  Nuclear mitochondrial pseudogenes (NUMTs) are DNA fragments transferred from mitochondria to the nucleus. They are a double-edged sword for phylogenetic analyses because of their independent evolutionary histories. Herein, we employed a targeted, PCR-based procedure to study NUMTs originated from a Nad1-12S fragment in two sibling fig wasps associated with Ficus hispida: Philotrypesis pilosa and Philotrypesis sp. These sibling fig wasps arising from sympatric speciation live in the same syconium, which makes them good models to investigate subtle behavioral and genetic divergences in similar ecological niches. Further investigation relies on a correct estimate of the separation time of both species. Through the analysis based on the acquired NUMTs, we found that the origin of the NUMTs in both species appears to be a very recent event; however they may arise in the common ancestor of both species. Since the NUMTs integration is a recent event, we assumed that these newly produced NUMTs evolve similarly to genuine mtDNA. Then we calculated the genetic divergence timing based on mitochondrial genes, an average substitution rate of about 2.3×10^-8 substitutions/site/year. These typical characters make them good ‘fossil’ markers to trace back the speciation time of both species back to 0.40-0.48 mya. The results suggest that some NUMTs are good ‘fossil’ markers for tracing back important evolutionary events including speciation.

Key words: Fig wasp, nuclear mitochondrial pseudogene (NUMT), purifying selection, mitochondrial DNA, speciation timing, ‘fossil&rsquo, marker