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Influence of consanguinity on the sex ratio and diapause of Diprion pini L. (Hym., Diprionidae) populations. II. Effect of inbreeding on diapause

Géri C., Allais J.P., Beaudoin L., Goussard F.. 1995. Journal of Applied Entomology, 119 (1-5) : p. 35-43.

DOI: 10.1111/j.1439-0418.1995.tb01240.x

Experiments were undertaken in 1990 and 1992 to prove the effect of consanguinity on diapause and to study its links with sex determinism and possible genetic factors. These experiments were realized on the progenies of colonies collected in Fontainebleau forest. From adult emergences in April different ways of breeding were comparatively carried out during two generations: inbred brother-sister crosses, non-inbred crosses with insects from another origin, in particular with a reference rearing strain reared for many generations; and breedings of virgin females. The progenies of these crossings were reared in the same standard laboratory conditions favourable to development without diapause (16°C, 15 h L-9 h D photoperiod for the young larvae, 20°C, 16 h 30 L-7 h 30 D thereafter). Diapause rates and sex-ratio were simultaneously observed. The results show an important increase in diapause rates and male rates in the progenies of inbred insects. We also found a link between sex and diapause, its rates being higher in males. On the other hand, crossings with the rearing strain corroborate the existence of a genetic factor strengthening diapause which would be eliminated in reared populations if only the without diapause insects are bred from generation to generation. Some hypotheses about the interaction between consanguinity, sex determinisms and the existence of this genetic factor are drawn from these results. It is suggested that these phenomena may have a noticeable importance for population dynamics of D. pini.

Mots-clés : diprion pini; diapause; sex ratio; inbreeding; structure de la population; lignée consanguine; croisement; Épreuve sur la descendance; france

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