Smith M Alex, Wood D Monty, Janzen Daniel H, Hallwachs Winnie, Hebert Paul D N
Biodiversity Institute of Ontario, University of Guelph, Guelph, ON, Canada N1G 2W1.
Proc Natl Acad Sci U S A. 2007 Mar 20;104(12):4967-72. doi: 10.1073/pnas.0700050104. Epub 2007 Mar 14.
Many species of tachinid flies are viewed as generalist parasitoids because what is apparently a single species of fly has been reared from many species of caterpillars. However, an ongoing inventory of the tachinid flies parasitizing thousands of species of caterpillars in Area de Conservación Guanacaste, northwestern Costa Rica, has encountered >400 species of specialist tachinids with only a few generalists. We DNA-barcoded 2,134 flies belonging to what appeared to be the 16 most generalist of the reared tachinid morphospecies and encountered 73 mitochondrial lineages separated by an average of 4% sequence divergence. These lineages are supported by collateral ecological information and, where tested, by independent nuclear markers (28S and ITS1), and we therefore view these lineages as provisional species. Each of the 16 apparently generalist species dissolved into one of four patterns: (i) a single generalist species, (ii) a pair of morphologically cryptic generalist species, (iii) a complex of specialist species plus a generalist, or (iv) a complex of specialists with no remaining generalist. In sum, there remained 9 generalist species among the 73 mitochondrial lineages we analyzed, demonstrating that a generalist lifestyle is possible for a tropical caterpillar parasitoid fly. These results reinforce the emerging suspicion that estimates of global species richness are likely underestimates for parasitoids (which may constitute as much as 20% of all animal life) and that the strategy of being a tropical generalist parasitic fly may be yet more unusual than has been envisioned for tachinids.
许多寄蝇科的苍蝇被视为广食性寄生蜂，因为从许多种类的毛虫中培育出的显然是单一物种的苍蝇。然而，在哥斯达黎加西北部瓜纳卡斯特自然保护区对数千种毛虫的寄蝇科苍蝇进行的一项正在进行的清查中，发现了400多种专食性寄蝇，只有少数是广食性的。我们对2134只属于所培育的16种最具广食性的寄蝇形态种的苍蝇进行了DNA条形码分析，发现了73个线粒体谱系，平均序列差异为4%。这些谱系得到了相关生态信息的支持，并且在经过测试的情况下，还得到了独立核标记（28S和ITS1）的支持，因此我们将这些谱系视为暂定物种。这16种显然具有广食性的物种中的每一种都分解为四种模式之一：（i）单一的广食性物种，（ii）一对形态上难以区分的广食性物种，（iii）一个专食性物种复合体加上一个广食性物种，或（iv）一个专食性物种复合体，没有剩余的广食性物种。总之，在我们分析的73个线粒体谱系中，仍有9种广食性物种，这表明热带毛虫寄生蝇有可能具有广食性生活方式。这些结果强化了一种新出现的怀疑，即全球物种丰富度的估计可能低估了寄生蜂（可能占所有动物生命的20%），而且作为热带广食性寄生蝇的策略可能比人们对寄蝇科的设想更为罕见。
