M. Beekman et al., Selection for non-diapause in the bumblebee Bombus terrestris, with notes on the effect of inbreeding, ENT EXP APP, 93(1), 1999, pp. 69-75
Bumblebees are generally believed to be annual insects. However, here we wi
ll show that under laboratory conditions the bumblebee Bombus terrestris (L
.) can produce a second generation without a period of cold storage (diapau
se) or CO2 narcosis (a method to break diapause). It is also shown that thi
s so-called non-diapause trait can be selected for. The percentage of non-d
iapausing queens increased from 8% (minimum) to 97% (maximum) in two genera
tions of selection. However, it was not possible to maintain isofemale non-
diapause lines. Colonies of the fourth and fifth generation remained small
(expressed in worker number) and produced a small number of queens. Also th
e percentage of queens that started laying eggs (defined as the percentage
non-diapause) decreased in the fourth and fifth generations. To study wheth
er this decline of the non-diapause lines was caused by inbreeding, a contr
ol experiment was conducted. In this control experiment queens were mated w
ith their brothers (full-sib mating) for several generations and the number
of queens that start egg laying was measured. This revealed that inbreedin
g can have a negative effect on the egg-laying capacities of queens thus ca
using the decline of inbred (non-diapause) lines.