Abstract
Northern Europe has 11 sympatric, monophagous pine sawflies (Diprionidae) feeding on Scots pine Pinus sylvestris. This paper describes patterns in the pine sawfly dynamics, and outlines the four major hypotheses that have been put forward to explain the patterns: plant defence (resistance), microparasites (virus), macroparasites (parasitoids), and generalist cocoon predators (shrews and omnivorous small mammals). The plant defence and cocoon predation hypotheses explain more observations about sawfly dynamics than the parasite hypotheses. One of the patterns is an association between gregarious larvae (five of the 11 species) and high outbreak frequency. The essential difference in population dynamics between the solitary and gregarious species is the risk-prone reproductive strategy of the latter, which increases the variance of density fluctuations. Chance dictates that gregarious species have occasional rapid build-ups of local populations, which may lead to an escape from the control of the regulating factors.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
