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PremiseThe success or failure of propagules in contrasting microhabitats may play a role in biological invasion. We tested for variation in demographic performance and phenotypic trait expression during invasion byAlliaria petiolatain different microhabitats. MethodsWe performed a reciprocal transplant experiment withAlliaria petiolatafrom edge, intermediate, and forest understory microhabitats to determine the roles of the environment and maternal source on traits, fecundity, population growth rates (λ), and selection. ResultsObservations ofin situpopulations show that edge populations had the highest density and reproductive output, and forest populations had the lowest. In experimental populations, population growth rates and reproductive output were highest in the edge, and the intermediate habitat had the lowest germination and juvenile survival. Traits exhibited phenotypic plasticity in response to microhabitat, but that plasticity was not adaptive. There were few effects of maternal source location on fitness components or traits. ConclusionsAlliaria petiolataappears to be viable, or nearly so, in all three microhabitat types, with edge populations likely providing seed to the other microhabitats. The intermediate microhabitat may filter propagules at the seed stage, but discrepancies betweenin situobservations and experimental transplants preclude clear conclusions about the role of each microhabitat in niche expansion. However, edge microhabitats show the highest seed output in both analyses, suggesting that managing edge habitats might reduce spread to the forest understory.
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Climate‐related geographical variation in performance traits across the invasion front of a widespread non‐native insect
Abstract AimInvasive species are ideal systems for testing geographical differences in performance traits and measuring evolutionary responses as a species spreads across divergent climates and habitats. The European gypsy moth,Lymantria dispar disparL. (Lepidoptera: Erebidae), is a generalist forest defoliator introduced to Medford, Massachusetts, USA in 1869. The invasion front extends from Minnesota to North Carolina and the ability of this species to adapt to local climate may contribute to its continuing spread. We evaluated the performance of populations along the climatic gradient of the invasion front to test for a relationship between climate and ecologically important performance traits. LocationEastern United States of America TaxonLymantria dispar disparL. (Lepidoptera: Erebidae) MethodsInsects from 14 populations across the US invasion front and interior of the invasive range were reared from hatch to adult emergence in six constant temperature treatments. The responses of survival, pupal mass and larval development time were analysed as a function of source climate (annual mean normal temperature), rearing temperature and their interaction using multiple polynomial regression. ResultsWith the exception of female development time, there were no significant interactions between source climate and rearing temperature, indicating little divergence in the shape of thermal reaction norms among populations. Source population and rearing temperature were significant predictors of survival and pupal mass. Independent of rearing temperature, populations from warmer climates had lower survival than those from colder climates, but attained larger body size despite similar development times. Larval development time was dependent on rearing temperature, but there were not consistent relationships with source climate. Main ConclusionsThermal adaptation can be an important factor shaping the spread of invasive species, particularly in the context of climate change. Our results suggest thatL. d. disparis highly plastic, but has undergone climate‐related adaptation in thermal performance and life‐history traits as it spread across North America.
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- Award ID(s):
- 1702701
- PAR ID:
- 10453494
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Biogeography
- Volume:
- 48
- Issue:
- 2
- ISSN:
- 0305-0270
- Format(s):
- Medium: X Size: p. 405-414
- Size(s):
- p. 405-414
- Sponsoring Org:
- National Science Foundation
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