Importantly this might indicate that past hybridization between banksi and pilosula with origination of alternative hybrid entities has successfully occurred more than once and that there could be more than one existing allodiploid banksi/pilosula hybrid clone present in south-eastern Australia.
Her daughter workers and gynes would have had the unmatched allodiploid karyology illustrated in Figure 2, compromising any normal reproductive future (for example, their gametes would be a statistical 50:50 mix of those of the two parental species).
Without our fortuitous knowledge of its allodiploid karyology, discovered by HTI in the course of a general cytological survey of Australian ants [1, 2], the eccentric nature of this remarkable species might never have been recognised.
In evolutionary terms, paternal ancestor individuals deriving from hybrids (androgens) play different roles in both the hybridogenetic and the parthenogenetic Bacillus reproductive systems: coexisting males of the fathering taxon are crucial for the maintenance of the hemiclonal system, whereas, through genome addition to the parthenogenetic eggs, they promote the production of polyploid clones from allodiploid females.
The ability of allodiploid females to act as nonhybrid individuals as they produce pure parental progeny, is an unprecedented finding.
Diploid hybridogenetic strains are associated with triploid gynogenetic taxa in the Poeciliopsis hybrid complex (Schultz and Kallman 1968; Schultz 1969); Bacillus stick insects are peculiar because hybridogenesis co-occurs with parthenogenesis in allodiploids arising from the same parental species pair (i.e., B.
carinata BBCC): Homoeologous pairing is more pronounced in the three-genome hybrids (TACC, TBAA, TCAA, TCBB) as compared to allodiploids
(TA, TB, TC).