Summary
Knowledge of intraspecific variation in symbioses may aid in understanding the ecology of widespread insects in different parts of their range. We investigated bacterial symbionts of
A
delges tsugae
, a pest of hemlocks in eastern
N
orth
A
merica introduced from
A
sia. Amplification, cloning, and sequencing of bacterial 16
S rDNA
,
in situ
hybridizations, and electron microscopy revealed that
A
. tsugae
harbours up to five bacterial phylotypes, according to population. Three
G
ammaproteobacteria
species are maternally transmitted. The first, designated ‘
C
a
.
P
seudomonas adelgestsugas’ resides in the haemocoel, and was detected in all populations except
T
aiwan. The second phylotype, ‘
C
a
.
S
erratia symbiotica’, resides in bacteriocytes of populations on
T
suga sieboldii
in
J
apan and in
E
.
N
orth
A
merica. The third phylotype, designated ‘
C
a
.
A
nnandia adelgestsuga’, clustered within a lineage of several insect endosymbionts that included
B
uchnera aphidicola
. It was detected in bacteriocytes in all populations, and in salivary glands of first instars. Two
B
etaproteobacteria
phylotypes were detected in some
J
apanese
T
. sieboldii
and eastern
N
orth
A
merica populations, and were observed only in salivary glands with no evidence of maternal transmission. Our results support the ideas that symbiont gain and loss has been volatile in adelgids, and that symbionts may help to trace the source of invasive species.