Rj. Stuart et R. Gaugler, GENETIC ADAPTATION AND FOUNDER EFFECT IN LABORATORY POPULATIONS OF THE ENTOMOPATHOGENIC NEMATODE STEINERNEMA-GLASERI, Canadian journal of zoology, 74(1), 1996, pp. 164-170
Laboratory culture can have detrimental effects on populations through
adverse environmental conditions such as poor nutrition or disease, o
r through genetic effects such as inbreeding depression, founder effec
t, genetic drift, or laboratory adaptation. We tested for laboratory e
ffects on the entomopathogenic nematode Steinernema glaseri (Steiner)
by forming a genetically diverse base population from a series of fiel
d isolates and rearing several independent lines through 12 cycles of
laboratory culture, using larvae of the greater wax moth, Galleria mel
lonella (L.), or the Japanese beetle, Popillia japonica Newman, as hos
ts. Laboratory bioassays based on G. mellonella indicated that lines m
aintained with large breeding populations did not deteriorate but ofte
n showed significant increases in infectivity (15.3-48.0%), proportion
of males (12.2-36.1%), and reproductive potential (39.0-160.4%). Line
s reared on P. japonica larvae responded similarly to lines reared on
G. mellonella but showed higher levels of reproductive potential. Two
of three lines subjected to initial genetic bottlenecks to test for fo
under effects differed from other lines by showing very high infectivi
ty but little change in sex ratio or reproductive potential. These res
ults demonstrate that laboratory adaptation can produce dramatic chang
es in important biological attributes of these nematodes, but that a l
ack of genetic variation associated with founder effects can impede th
is process. Laboratory adaptation should be considered a potent factor
when designing, interpreting, and comparing studies of this important
group of biological control organisms.