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The emerald ash borer (Agrilus planipennis, Coleoptera: Buprestidae) is a wood-boring invasive pest devastating North American ash (Fraxinus spp.). A. planipennis overwinters primarily as a freezeavoiding prepupa within the outer xylem or inner bark of the host tree. The range of this species is expanding outward from its presumed introduction point in southwestern Michigan. We hypothesized that loss of cold tolerance in response to mid-winter warm spells could limit survival and northern distribution of A. planipennis. We determined whether winter-acclimatised A. planipennis prepupae reduced their cold tolerance in response to mid-winter warm periods, and whether this plasticity was reversible with subsequent cold exposure. Prepupae subjected to mid-winter warm spells of 10 and 15°C had increased supercooling points (SCPs) and thus reduced cold tolerance. This increase in SCP was accompanied by a rapid loss of haemolymph cryoprotectants and the loss of cold tolerance was not reversed when the prepupae were returned to -10°C. Exposure to temperatures fluctuating from 0 to 4°C did not reduce cold hardiness. Only extreme warming events for several days followed by extreme cold snaps may have lethal effects on overwintering A. planipennis populations. Thus, distribution in North America is likely to be limited by the presence of host trees rather than climatic factors, but we conclude that range extensions of invasive species could be halted if local climatic extremes induce unidirectional plastic responses.

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While best practices for evaluating restoration ecology projects are emerging rapidly, budget constraints often limit postrestoration monitoring, which emphasizes the need for practical and efficient monitoring strategies. We examined the postrestoration outcome for an ENGO (Nature Conservancy of Canada) project, to assess retroactively how variation in intensity and frequency of sampling would have affected estimates of plant species composition, diversity, and richness over time. The project restored four habitat types (mesic forest, oak woodland, wet meadow, and sand barren) using sculptured seeding of tallgrass prairie and woody species. Species-level plant cover was monitored annually for 10 years in 168 2 × 2-m quadrats. We performed randomization tests to examine estimates of species diversity and richness as a function of the number of quadrats sampled, and assessed the necessity of annual sampling for describing changes in species composition and successional trajectories. The randomization tests revealed that sampling 10-17 quadrats, depending on habitat type, was sufficient to obtain estimates of species diversity that were at least 95% of values obtained from the whole dataset. Species richness as a function of number of quadrats sampled did not plateau, which suggests that rather than increasing the number of sampling quadrats, richness could be estimated more efficiently using nonquadrat based sampling techniques. Nonmetric multidimensional scaling analysis revealed that plant species composition largely stabilized by 3-5 years postrestoration depending on habitat type. By that time, native, seeded species dominated the restoration, and the benefits of annual sampling for tracking changes in species composition diminished.