Multiple choice of Aphalara itadori for oviposition among three knotweed species

Intraspecific hybridization between distinct populations could increase
fitness and adaptive potential of biological control agents that often
have low genetic diversity and can be inbred due to long-term laboratory
rearing often at small population sizes. Hybridization can also alter host
preference and performance when the parental insect populations are
adapted to different host plants. We investigated the effects of
hybridization between two populations (Northern and Southern) of the
psyllid, Aphalara itadori, that have different fitness on three invasive
knotweed species (Japanese, giant, and Bohemian). Fecundity, host choice,
and developmental success of second-generation reciprocal hybrids and the
parental psyllid populations were compared on the three knotweed species
in multiple choice tests. Hybridization did not increase fecundity. All
three knotweed species were accepted for oviposition without preference by
the Southern and the two hybrid psyllid populations. The northern psyllid
population laid the most eggs on Bohemian knotweeds but those were
maladaptive choices since almost all eggs failed to develop. Developmental
success of the parental psyllid populations was highest on the knotweed
species they were originally collected from, on Japanese knotweed of the
Southern psyllids and on giant knotweed of the Northern psyllids. Hybrids
had intermediate or higher survival on given knotweed hosts compared to
their parents. These results can inform release tactics of A. itadori in
different regions especially where there appears to be climatic and/or
host mismatches such as in Michigan. In southern Michigan, based on
climate the Northern psyllid population should be released. However, the
most common knotweed species in the region are Bohemian and Japanese
knotweeds that do not support development of the Northern psyllids. In
this case, hybrids that may carry cold adaptations of the Northern
psyllids but have better developmental success on the prevailing knotweed
species may be considered for release to increase establishment success.