Will the real Bemisia tabaci please stand up?

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.

Figure 1. Schematic diagram detailing sequencing of the Gennadius 1889 Bemisia tabaci mtCOI amplicons using primers listed in Table 1.

The final 496 bp contig was assembled from five amplicons (primer pairs 1+2; 3+4; 5+9; 3+6; 7+8).

Figure 2. Illustrations of a puparium (I, J), variations in the cement gland of three adult females (C–E) and lateral view of aedeagus of an adult male (H) from Bemisia tabaci specimens collected by Gennadius from tobacco in Agrinio, Greece in 1889.

In addition, illustrations of the antenna (A) and cement gland (B) of a female and the antenna (F) and posterior apex of an adult male (G) of specimens collected in China and determined to be Mediterranean based on DNA analysis.