Establishment and expansion of a Thaumetopoea pityocampa (Den. & Schiff.) (Lep. Notodontidae), population with a shifted life cycle in a production pine forest, Central-Coastal Portugal

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Abstract

In 1997, a temporally shifted population of Thaumetopoea pilyocampa (Den. & Schiff.), was recorded for the first time in a restricted area of the oldest National Pine Forest of Portugal-the National Pine Forest of Leiria. This new population larval development takes place during the summer (summer population-SP), while in the normal population it takes place during the winter (winter population-WP). Between 2000 and 2003, we assessed the distribution and expansion of the SP, and quantified the differences in population densities, mortality and major life history traits with the WP within the Leiria Forest. The SP occurred at higher population levels (5-35% attacked trees) in a large continuous area of young plantations with high tree density, the same area where it was initially discovered. These densities were higher than the ones recorded for the WP in any part of the forest (0-12%), although both populations coexist geographically. The temporally shifted population preferably attacked young plantations. It also expanded south, following the direction of the dominant winds during adult flight. SP had a lower fecundity than the WP, however it benefited from lower egg mortality due mostly to a low rate of parasitism. It also benefited from a lower mortality in the early larval instars leading to low levels of colony extinction. SP larvae take half the time compared to the WP larvae, to reach the same final mass, probably due to the fact that they develop under higher temperature and global radiation. Separated emergence timings of adults lead to an allochronic isolation of the two populations. However, if this might represent an allochronic speciation event has to await further ecological and evolutionary studies of the system. (c) 2006 Elsevier B.V. All rights reserved.

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  • Biological Sciences
Original languageEnglish
Pages (from-to)108-115
JournalForest Ecology and Management
Volume233
Issue number1
Publication statusPublished - 2006
Publication categoryResearch
Peer-reviewedYes