L. Keller et L. Passera, INCEST AVOIDANCE, FLUCTUATING ASYMMETRY, AND THE CONSEQUENCES OF INBREEDING IN IRIDOMYRMEX-HUMILIS, AN ANT WITH MULTIPLE QUEEN COLONIES, Behavioral ecology and sociobiology, 33(3), 1993, pp. 191-199
Inbreeding may have important consequences for the genetic structure o
f social insects and thus for sex ratios and the evolution of socialit
y and multiple queen (polygynous) colonies. The influence of kinship o
n mating preferences was investigated in a polygynous ant species, Iri
domyrmex humilis, which has within-nest mating. When females were pres
ented simultaneously with a brother that had been reared in the same c
olony until the pupal stage and an unrelated male produced in another
colony, females mated preferentially with the unrelated male. The role
of environmental colony-derived cues was tested in a second experimen
t where females were presented with two unrelated males, one of which
had been reared in the same colony until the pupal stage (i.e., as in
the previous experiment), while the other had been produced in another
colony. In this experiment there was no preferential mating with fami
liar or unfamiliar males, suggesting that colony-derived cues might no
t be important in mating preferences. Inbreeding was shown to have no
strong effect on the reproductive output of queens as measured by the
number of worker and sexual pupae produced. The level of fluctuating a
symmetry of workers produced by inbreeding queens was not significantl
y higher than that of non-inbreeding queens. Finally, colonies headed
by inbreeding queens did not produce adult diploid males. Based on the
current hypotheses of sex-determination the most plausible explanatio
ns for the absence of diploid-male-producing colonies are that (i) wor
kers recognized and eliminated these males early in their development,
and/or (ii) there are multiple sex-determining loci in this species.
It is suggested that even if inbreeding effects on colony productivity
are absent or low, incest avoidance mechanisms may have evolved and b
een maintained if inbreeding queens produce a higher proportion of una
viable off-spring.