loading page

Impacts of biotic and abiotic variation within and among trees on body size, sex ratio, and survival in immature stages of the European woodwasp, Sirex noctilio
  • Jeff Garnas,
  • Katie Vann,
  • Brett Hurley
Jeff Garnas
University of New Hempshire
Author Profile
Katie Vann
Weyerhaeuser Company
Author Profile
Brett Hurley
University of Pretoria
Author Profile

Abstract

Resource quality has direct or indirect effects on female oviposition choice, offspring performance, and ultimately on body size and sex ratios. We examined these patterns in Sirex noctilio Fabricus, the globally invasive European pine woodwasp, in South African Pinus patula plantations. We studied how natural variation in biotic and abiotic factors influenced sex-specific density, larval growth rates, and survival. Twenty trees infested trees divided into top, middle, and bottom sections were sampled at three time points during larval developmental. We measured moisture content, bluestain colonization, and co-occurring insect density and counted, measured, and sexed all immature wasps. A subset of larval tunnels was measured to assess compensatory feeding and growth efficiency. Wasp density increased from the bottoms to the tops of trees for both males and females. However, the largest individuals and the longest tunnels were found in bottom sections. Male bias was strong (~10:1) and likewise differed among sections, with the highest proportion in the middle and top sections. Sex ratios became more strongly male biased due to high female mortality, especially in top and middle logs. Biotic and abiotic factors such as colonization by Diplodia sapinea, weevil (Pissodes spp.) density, and wood moisture explained modest residual variation in our primary mixed effects models, generally between 6-12%. These findings contribute to a more comprehensive understanding of sex-specific resource quality for S. noctilio and of how variation in key biotic and abiotic factors can influence body size, sex ratio and survival in this economically important woodwasp.

Peer review status:UNDER REVIEW

24 Jul 2020Submitted to Ecology and Evolution
25 Jul 2020Submission Checks Completed
25 Jul 2020Assigned to Editor
30 Jul 2020Reviewer(s) Assigned
12 Aug 2020Review(s) Completed, Editorial Evaluation Pending
21 Aug 2020Editorial Decision: Revise Minor
20 Sep 20201st Revision Received
22 Sep 2020Submission Checks Completed
22 Sep 2020Assigned to Editor
22 Sep 2020Review(s) Completed, Editorial Evaluation Pending