Abstract
Since Panayiotis Gennadius first identified the whitefly, Aleyrodes tabaci in 1889, there have been numerous revisions of the taxonomy of what has since become one of the world's most damaging insect pests. Most of the taxonomic revisions have been based on synonymising different species under the name Bemisia tabaci. It is now considered that there is sufficient biological, behavioural and molecular genetic data to support its being a cryptic species complex composed of at least 34 morphologically indistinguishable species. The first step in revising the taxonomy of this complex involves matching the A. tabaci collected in 1889 to one of the members of the species complex using molecular genetic data. To do this we extracted and then amplified a 496 bp fragment from the 3′ end of the mitochondrial DNA cytochrome oxidase one (mtCOI) gene belonging to a single whitefly taken from Gennadius' original 1889 collection. The sequence identity of this 123 year-old specimen enabled unambiguous assignment to a single haplotype known from 13 Mediterranean locations across Greece and Tunisia. This enabled us to unambiguously assign the Gennadius A. tabaci to the member of the B. tabaci cryptic species complex known as Mediterranean or as it is commonly, but erroneously referred to, as the ‘Q-biotype’. Mediterranean is therefore the real B. tabaci. This study demonstrates the importance of matching museum syntypes with known species to assist in the delimitation of cryptic species based on the organism's biology and molecular genetic data. This study is the first step towards the reclassification of B. tabaci which is central to an improved understanding how best to manage this globally important agricultural and horticultural insect pest complex.
Highlights
In 1889, Panayiotis Gennadius, an Inspector of Agriculture, was sent to Agrinio, Greece to identify the small fly-like pest that was devastating tobacco crops there
This study shows how we succeeded in extracting DNA from an intact whitefly that was part of the 1889 collection and amplifying the mitochondrial DNA cytochrome oxidase one (mtCOI) and unambiguously matching it to a known member of the B. tabaci complex, and determining its true identity
The differences in mtCOI between the different putative species make the assignment of the B. tabaci that Gennadius collected in 1889, unambiguous
Summary
In 1889, Panayiotis Gennadius, an Inspector of Agriculture, was sent to Agrinio, Greece to identify the small fly-like pest that was devastating tobacco crops there. From the late 1880s to the early 1980s, outbreaks were sporadic and relatively small, but this changed in the mid-1980s with widespread outbreaks occurring across the south western USA [5] This was odd because this pest was well known across the region as a minor pest yet here it was destroying crops. Researchers concluded that while there were no morphological differences, there were sufficient molecular and biological differences to indicate that the outbreak pest was a different species [6]. This touched off a debate that has continued until today [7,8,9,10]
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