Abstract
When the cerambycid, Phoracantha recurva, invaded California in the mid 1990’s a parasitoid wasp was imported from its native range in Australia as part of a biological control program. The wasp was later identified to be Avetianella longoi, which had already been released years earlier to control the congener longhorned beetle, Phoracantha semipunctata. Despite being recognized as the same species, the two wasps exhibited differential success on P. recurva eggs, indicating the presence of two separate strains. Here we determine if the differentiating factor between the two strains of A. longoi is a heritable genetic trait. All four pairings between the two strains were conducted, resulting in two homogenous and two heterogeneous crosses. All crosses except one produced viable F1 female offspring. F1 females were allowed to oviposit on P. recurva eggs and the survival of their offspring was compared to determine if survival can be affected by paternal contributions. The result was that the offspring of females with fathers from the second introduced strain showed significantly increased survival compared to F1 females with parents from the first introduced strain. This increased survival demonstrated that there is a heritable dominant trait that is associated with increased survival on P. recurva host eggs.
Highlights
Hymenopteran endoparasitoids spend at least a portion of their development within the body of their host and utilize this host as their source of nourishment
Based on the higher rate of survival in the hybrid strain compared to the S strain it indicates that avoiding encapsulation in P. recurva is due to a heritable difference in the R strain that the S strain lacks
It is possible to rule out the differentiating factor between the two strains, with respect to the immune response of P. recurva, being due to the presence of an immune triggering factor in the S strain as the S♀R♂ strain would inherit this factor and provoke an immune response like their mother
Summary
Hymenopteran endoparasitoids spend at least a portion of their development within the body of their host and utilize this host as their source of nourishment For this strategy to be successful, the parasitoid must avoid being killed by the host’s innate immune response. Immune responses can be suppressed by injected material, such as venom or polydnaviruses (PDVs), which causes the alteration of host characteristics or blocks immune pathways [3, 4, 5, 6] These mechanisms of circumventing host immune responses can be passed on to the generation in either through parental DNA or through vertical transmission of associated organisms. Parental genes control the formation of proteins that comprise venom
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