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Sexual selection maintains whole-body chiral dimorphism in snails
journal contributionposted on 2023-06-07, 21:20 authored by M Schilthuizen, P G Craze, A S Cabanban, A Davison, J Stone, E Gittenberger, B J Scott
Although the vast majority of higher animals are fixed for one chiral morph or another, the cause for this directionality is known in only a few cases. In snails, for example, rare individuals of the opposite coil are unable to mate with individuals of normal coil, so directionality is maintained by frequency-dependent selection. The snail subgenus Amphidromus presents an unexplained exception, because dextral (D) and sinistral (S) individuals occur sympatrically in roughly equal proportions (so-called antisymmetry) in most species. Here we show that in Amphidromus there is sexual selection for dimorphism, rather than selection for monomorphism. We found that matings between D and S individuals occur more frequently than expected by chance. Anatomical investigations showed that the chirality of the spermatophore and the female reproductive tract probably allow a greater fecundity in such interchiral matings. Computer simulation confirms that under these circumstances, sustained dimorphism is the expected outcome.
JournalJournal of Evolutionary Biology
Page range1941 - 1949
Department affiliated with
- Biology and Environmental Science Publications
NotesJointly conceived study. Designed programs simulating chiral organisms where mating preference was manipulated. Developed statistical test for observed mating preferences. Wrote Methods and some Results. The study examines the fundamental metazoan body plan and polymorphism maintenance. The finding that sexual selection can maintain such basic dimorphism was novel and unexpected.
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