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Updated: Feb 16, 2026

Assessing Agrochemical Risk to Mated Honey Bee Queens
Published on: March 3, 2021
Parthenogenetic flatworms have more symbionts than their coexisting, sexual conspecifics, but does this support the
N K Michiels1, L W Beukeboom1, N Pongratz1
1Max-Planck-Institut für Behavioural Physiology, Starnberg, GermanyInstitute for Evolutionary and Ecological Sciences, University of Leiden, PO Box 9516, NL-2300 RA Leiden, The Netherlands.
Abstract:
The Red Queen hypothesis predicts that sexuality is favoured when virulent parasites adapt quickly to host genotypes. We studied a population of the flatworm Schmidtea polychroa in which obligate sexual and parthenogenetic individuals coexist. Infection rates by an amoeboid protozoan were consistently higher in parthenogens than in sexuals. Allozyme analysis showed that infection was genotype specific, with the second most common clone most infected. A laboratory measurement of fitness components failed to reveal high infection costs as required for the Red Queen. Although fertility was lower in more infected parthenogens, this effect can also be explained by the accumulation of mutations. We discuss these and other characteristics of our model system that may explain how a parasite with low virulence can show this pattern.
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