Extensive chromosomal variation associated with taxon divergence and host specificity in the gall-inducing scale insect Apiomorpha munita (Schrader) (Hemiptera: Sternorrhyncha: Coccoidea: Eriococcidae)

Apiomorpha Rübsaamen (Hemiptera: Coccoidea: Eriococcidae) is one of the most chromosomally diverse of all animal genera. There is extensive karyotypic variation within many of the morphologically defined species, including A. munita (Schrader) which is here reported to have diploid chromosome counts ranging from 6 to more than 100. Each of the three morphologically defined subspecies of A. munita also displays considerable chromosomal variation: A. m. tereticornuta Gullan (2n = 6, 8, 20, 22 or 24), A. m. malleensis Gullan (2n = 6, 20, 22, 24 or 26), and A. m. munita (Schrader) (2n = 54 or >100). Apiomorpha munita appears to occur only on eucalypts of the informal subgenus Symphyomyrtus, with each of the subspecies of A. munita restricted to discrete symphyomyrt sections. Several different karyotypic forms within each subspecies of A. munita appear to be restricted to only one or a few eucalypt species or series. The association between apparent host specificity and chromosomal rearrangements in A. munita suggests that both may be playing an active role in taxon divergence in Apiomorpha.