Biological Invasions (2017) 19, 1431-1447

Tonya D. Bittner, Ann E. Hajek, Laurel Haavik, Jeremy Allison and Helen Nahrung (2017)
Multiple introductions of Sirex noctilio (Hymenoptera: Siricidae) in northeastern North America based on microsatellite genotypes, and implications for biological control
Biological Invasions 19 (5), 1431-1447
Abstract: The invasive woodwasp Sirex noctilio (Hymenoptera: Siricidae) has been moved from Eurasia into regions in the Southern Hemisphere, where extensive tree mortality has occurred in pines (Pinus spp.) introduced for forestry. More recently this woodwasp was found in northeastern North America, where pines are native, and it is a species of concern due to the economic importance of pines. Understanding the genetic diversity of North American S. noctilio points to new areas of inquiry, particularly regarding the ability of parasitic nematodes to sterilize woodwasps, which could provide control methods in the US and/or Canada. We investigated the genetic diversity of 924 S. noctilio from nine populations from New York and Pennsylvania (US), Ontario (CA), and Queensland (AU) using nine microsatellite loci. To avoid inflating the number of populations estimated by Bayesian inference, we measured the full-sibling relationships of woodwasps within 13 trees and removed all but one member of each full-sib family from the genetic analysis, resulting in a final sample size of 741 S. noctilio. Within a tree, on average 39% of woodwasps did not have a full sibling, and there were 5.6 families with at least two full-sibling members per tree. The mean family size across trees was 1.9 when single offspring (i.e., no full siblings) were included. Given the short time span since invasion, variation within North American S. noctilio is likely due to differences among founding genotypes. Genetic analyses support the hypothesis that at least two separate introductions occurred. Within North America, genetic distance measures were greatest between a site in southwestern Ontario and all other sites, suggesting that this population could represent a separate introduction event. Two methods of Bayesian clustering also support this idea; they detected 4 or 5 distinct genetic clusters with little admixture between the southwestern Ontario site and other North American populations. The wasps from Australia, where biological control with nematodes has been successful, showed low genetic diversity and clustered with the southwestern Ontario population in one out of two Bayesian analyses. Within the Ontario subset of samples, high woodwasp activity level (i.e., attack and mortality of trees) was associated with one genetic cluster more strongly than another. Population variation should be taken into account in studies of S. noctilio spread and management within North America.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Ann E. Hajek, Helen F. Nahrung, Laurel J. Haavik, Jeremy D. Allison

Research topic(s) for pests/diseases/weeds:
new introduction of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Sirex noctilio		Canada (east)
	Sirex noctilio		U.S.A. (NE)
	Sirex noctilio		Australia (NT+QLD)