Gender-role alternation in the simultaneously hermaphroditic freshwater snail <Emphasis Type="Italic">Physa acuta</Emphasis>: not with the same partner |
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Authors: | Benoît Facon Virginie Ravigné Jérôme Goudet |
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Institution: | (1) Department of Ecology and Evolution, University of Lausanne, Biophore, 1015 Dorigny, Switzerland;(2) UMR BGPI, Centre de coopération Internationale en Recherche Agronomique pour le Développement, Campus International de Baillarguet, TA A 54/K, 34398 Montpellier Cedex 05, France;(3) Present address: Institut des Sciences de l’Evolution, cc65, Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France |
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Abstract: | In simultaneous hermaphrodites, gender conflicts that arise from two potential mates sharing the same gender preference may
be solved through conditional reciprocity (or gamete trading). Conditional reciprocity had initially been considered widespread,
but recent studies suggest that its real occurrence may have been overestimated, possibly because most mating observations
have been performed on isolated pairs of individuals. Some resulting patterns (e.g., non-random alternation of sexual roles)
were indeed compatible with conditional reciprocity but could also have stemmed from the two partners independently executing
their own mating strategy and being experimentally enforced to do so with the same partner. Non-random alternation of gender
roles was recently documented in the simultaneously hermaphroditic freshwater snail Physa acuta. To distinguish between conditional and unconditional gender alternations, we observed copulations of individually marked
snails reared at three contrasted densities. We showed that density affected the overall frequency of copulations during the
first 2 days of the experiment with high-density boxes showing more copulations than low density boxes, but it did not affect
gender alternation patterns. A change in gender role was observed more often than expected by chance over two successive copulations
by the same individual, confirming previous studies. However, gender switches did not preferentially occur with the same partner.
We conclude that gender alternation is not due to conditional reciprocity in P. acuta. It may rather stem from each individual having a preference for gender alternation. We finally discuss the mechanisms and
the potential extent of this unconditional reciprocity. |
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Keywords: | Mating behaviour Conditional reciprocity Hermaphroditic freshwater snail Sex role alternation |
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