Host Specificity in the Honeybee Parasitic Mite, <i>Varroa spp</i>. in <i>Apis mellifera</i> and <i>Apis cerana</i>

<div><p>The ectoparasitic mite <i>Varroa destructor</i> is a major global threat to the Western honeybee <i>Apis mellifera</i>. This mite was originally a parasite of <i>A</i>. <i>cerana</i> in Asia but managed to spill over into colonies of <i>A</i>. <i>mellifera</i> which had been introduced to this continent for honey production. To date, only two almost clonal types of <i>V</i>. <i>destructor</i> from Korea and Japan have been detected in <i>A</i>. <i>mellifera</i> colonies. However, since both <i>A</i>. <i>mellifera</i> and <i>A</i>. <i>cerana</i> colonies are kept in close proximity throughout Asia, not only new spill overs but also spill backs of highly virulent types may be possible, with unpredictable consequences for both honeybee species. We studied the dispersal and hybridisation potential of <i>Varroa</i> from sympatric colonies of the two hosts in Northern Vietnam and the Philippines using mitochondrial and microsatellite DNA markers. We found a very distinct mtDNA haplotype equally invading both <i>A</i>. <i>mellifera</i> and <i>A</i>. <i>cerana</i> in the Philippines. In contrast, we observed a complete reproductive isolation of various Vietnamese <i>Varroa</i> populations in <i>A</i>. <i>mellifera</i> and <i>A</i>. <i>cerana</i> colonies even if kept in the same apiaries. In light of this variance in host specificity, the adaptation of the mite to its hosts seems to have generated much more genetic diversity than previously recognised and the <i>Varroa</i> species complex may include substantial cryptic speciation.</p>