Arrhenotokous parthenogenesis & mate-finding Allee effect in parasitoids
Anaïs Bompard  1@  , Xavier Fauvergue  2@  , Isabelle Amat  3@  , Thierry Spataro  1, 4@  
1 : Institut d'écologie et des sciences de l'environnement de Paris  (IEES)
Institut de recherche pour le développement [IRD], Université Paris-Est Créteil Val-de-Marne (UPEC), Université Pierre et Marie Curie (UPMC) - Paris VI, CNRS : UMR7618
Campus de Jussieu, 7 quai Saint Bernard, 75005 Paris -  France
2 : Institut Sophia Agrobiotech  (ISA)  -  Website
Institut National de la Recherche Agronomique - INRA, Centre National de la Recherche Scientifique - CNRS, Université Nice Sophia Antipolis
400 route des Chappes 06904 Sophia Antipolis -  France
3 : Laboratoire de Biométrie et Biologie Evolutive  (LBBE)  -  Website
CNRS : UMR5558, Université Claude Bernard - Lyon I (UCBL), INRIA
43 Bld du 11 Novembre 1918 69622 VILLEURBANNE CEDEX -  France
4 : Ecologie, Adaptation, Interactions
AgroParisTech
16 rue Claude Bernard, 75005 Paris -  France

Mating failures at low density – a common type of Allee effect – can reduce the per capita reproductive rate and, if severe enough, doom small populations to extinction. Parasitoids frequently undergo low densities triggered by their typically cyclic dynamic and/or the bottlenecks they experience when introduced for the biological control of agricultural pests. However, most parasitoid species belong to the order Hymenoptera and reproduce via arrhenotokous parthenogenesis: unfertilized eggs develop into males. A common belief is therefore that parasitoids are immune to the mate-finding Allee effect because mating failures yields more males, which should in turn restore mating success. Yet, meta-analyses of biological control introductions suggest that hymenopteran parasitoids are as extinction-prone as non-parthenogenetic species. Here we developed a population dynamic model to investigate the advantage of arrhenotokous parthenogenesis for parasitoid species that experience a mate-finding Allee effect. We show that: i) the conditions for which mating failures drive parasitoids to extinction are marginally more restricted for parthenogenetic species than for non-parthenogenetic ones; ii) parthenogenesis increases the resistance of parasitoids to accidental decrease in density and to invasions by a competing species whether or not parthenogenetic; and iii) parthenogenesis favors population establishment in new environments, whether or not already occupied. Hence even if arrhenotokous parthenogenesis is not as effective as expected to limit parasitoid extinctions caused by mating failures, it provides a significant advantage for population establishment and persistence.


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