Cytogenetics of ticks (Acari: Ixodoidea)

Haemaphysalis longicornis consists of diploid bisexual races (20+ XX♀; 20+X♂), triploid obligatory parthenogenetic races (30–35 chromosomes) and an aneuploid race capable of bisexual and parthenogenetic reproduction (22–28 chromosomes). Karyotypes were analyzed for each race. Hybridization failed between diploid and triploid races, but succeeded between bisexual diploid males and parthenogenetic aneuploid females. F1 and F2 progeny were produced and their chromosomes studied. Crossing of F1 progeny to a bisexual race was successful. Parthenogenetic ability was almost completely lost in F1 and F2 females. Several possible modes of evolution from diploid bisexual individuals to triploid parthenogenetic ones are discussed as is species characterization in taxa with races reproducing bisexually, parthenogenetically and by a combination of both methods.