Effects of inbreeding in the Glanville fritillary butterfl y (Melitaea cinxia)

Abstract

Previous studies suggest that inbreeding depression may be strong enough to elevate the rate of extinction of local populations in a metapopulation of the Glanville fritillary butterfl y. Laboratory experiments were conducted to assess the consequences of inbreeding for fi tness components through two generations of inbreeding. Clutch size, egg hatching rate, survival of the progeny until diapause and larval weight at diapause were measured in crosses between individuals from different small populations and in within-family crosses. The magnitude of inbreeding depression did not differ signifi cantly between the two generations, with the exception that there was a marked increase in the proportion of pairs that failed to produce any offspring in the second generation of full-sib mating. As expected, the effect of inbreeding on clutch size was evident only in the second generation, where the parents themselves were highly inbred. Inbreeding depression of the magnitude reported here can explain the increased extinction risk of natural small populations of the Glanville fritillary butterfl y.