Data from: A second New World hover fly, Toxomerus floralis (Fabricius) (Diptera: Syrphidae), recorded from the Old World, with description of larval pollen-feeding ecology

Recently (2013–2014), several hoverfly specimens from two localities in Benin and Cameroon (West and Central Africa) were caught from a species that we could not identify using existing identification keys for Afrotropical Syrphidae. Specific identification as Toxomerus floralis (Fabricius) was accomplished using morphology and various Neotropical identification keys. Corroboration of this identification was made by sequencing of the standard COI barcode region and a subsequent BLAST-IDS in BOLD that revealed a 100% sequence similarity with Toxomerus floralis from Suriname (South America). Species identification was further supported by sequencing parts of the nuclear 18S and 28S rRNA genes. The species is widespread in Togo, Benin, Nigeria and Cameroon, and eggs, larvae and adults are abundant at several localities. Yet, the full extent of its geographic distribution within tropical Africa remains to be determined. This is only the second known established introduction of a non-African hoverfly species in the Afrotropics. Interestingly, the larvae of the species have been reported as predators of Aphididae and Delphacidae but we found them to be pollenivorous, which is a rare feeding mode within the subfamily Syrphinae. Moreover, it is the only known Syrphinae species of which the larvae feed on pollen from two plant species from different families (Cyperaceae and Orobranchaceae). This example illustrates how DNA barcoding may allow a fast and accurate identification of introduced species.

2013—2014年期间，研究人员从贝宁（Benin）与喀麦隆（Cameroon）这两个分别位于西非、中非的采样点采集到数份食蚜蝇（hoverfly）标本。依托现有的非洲热带区食蚜蝇科（Afrotropical Syrphidae）分类检索表，无法对该物种进行准确鉴定。后续结合形态学特征与新热带区的多套分类检索表，最终将其鉴定为花斑小蚜蝇（Toxomerus floralis，Fabricius）。为佐证该鉴定结果，研究人员对标准COI条形码区域进行了测序，并在生命条形码数据系统（BOLD）中开展BLAST物种鉴定（BLAST-IDS），结果显示该序列与来自南美苏里南（Suriname）的花斑小蚜蝇序列相似度高达100%。此外，对核基因18S与28S核糖体RNA（rRNA）的部分区段进行测序，也为物种鉴定提供了额外支持。该物种目前已知广泛分布于多哥（Togo）、贝宁、尼日利亚（Nigeria）与喀麦隆，在多个采样点均发现了大量的卵、幼虫与成虫个体。不过，其在热带非洲境内的完整地理分布范围仍有待进一步探明。这是已知的第二种在非洲热带区（Afrotropics）成功定殖的非本土食蚜蝇物种。值得关注的是，此前有文献记载该物种幼虫为蚜科（Aphididae）与飞虱科（Delphacidae）的捕食性天敌，但本次研究发现其幼虫实际为食粉性，这种取食模式在食蚜蝇亚科（Syrphinae）中较为罕见。更为特殊的是，该物种亦是目前已知唯一一种幼虫取食来自两个不同科植物——莎草科（Cyperaceae）与列当科（Orobranchaceae）——花粉的食蚜蝇亚科物种。本案例充分证明，DNA条形码（DNA barcoding）技术可实现外来引入物种的快速且精准鉴定。