Morphological and Physiological Correlates of Hybrid Parthenogenesis

Asexuality frequently evolves in association with hybridity and polyploidy. The phenotypic consequences of this association must be understood before we can fully appreciate the reason for the short-term success, and the long-term failure, of asexual genetic systems. Parthenogenetic forms within the Australian gecko complex Heteronotia binoei are triploid hybrids and overlap geographically with both of their parental taxa as well as another sexual lineage. We compared nine morphological and nine physiological traits in wild-caught adult sexual and asexual individuals as well as their captive-bred progeny across a 1,200-km latitudinal gradient. Genome dosage effects were apparent in that the parthenogens were most phenotypically similar to the parental form for which they had a double dosage. Physiological differences between parthenogens and sexuals were often in the opposite direction of that expected under heterosis. Sympatric populations of sexual and parthenogenetic H. binoei differ in ecologically significant phenotypic traits, possibly reducing niche overlap. In keeping with the Red Queen hypothesis, parthenogenetic H. binoei had more ectoparasitic mites than did sexuals in some regions. Lizards with high mite loads also had high rates of evaporative water loss, suggesting a direct link between phenotypic traits and vulnerability to parasites.