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Lupinus nootkatensis is an exotic plant species that has been used for large‐scale sowing all around Iceland for land reclamation of eroded surfaces protected from livestock grazing.Until the early 1990s, L. nootkatensis was free from any significant arthropod herbivory in Iceland, whereas, after 1991, many outbreaks of native insect species, primarily Ceramica pisi and Eupithecia satyrata, have been recorded. These outbreaks have caused repeated total defoliation of extensive areas of L. nootkatensis, although the effects on its development are mostly unknown.We studied the effect of: (i) reduced herbivory; (ii) increased herbivory; and (iii) simulated increased herbivory, compared with (iv) unmanipulated herbivory, on defoliation and seed production of L. nootkatensis in a 3‐year field study within two sites at contrasting ages and successional stages.The results obtained showed that: (i) seed production across all treatments was negatively related to defoliation; (ii) reduced herbivory had a positive effect on the number of flowering stems and seed yield; and (iii) these effects depended on age and/or the successional stage because they were only significant in the older L. nootkatensis site.These findings indicate that arthropod herbivory may affect the invasiveness of L. nootkatensis in Iceland by reducing the seed production and the spatial distribution rate of late successional lupin communities. [ABSTRACT FROM AUTHOR]

The broom moth Ceramica pisi, a native species in Iceland, has shown a marked expansion from south Iceland towards the north, concurrent with increasing temperatures.Winter temperatures have increased more than summer temperatures in Iceland and, in the present study, the hypothesis was that the winter warming has facilitated the range shift of C. pisi.Winter survival of pupae in Iceland was studied in the laboratory. Pupae were collected in the autumn of 2012 at five separate locations, then weighed and placed at temperatures from −6 to −18 °C. One month after the sub‐zero treatments, the pupae were placed at room temperature and pupal emergence was recorded.No significant effect of sub‐zero treatments on the survival of C. pisi pupae was found. The primary hypothesis of the present study was therefore rejected.The major factor affecting low temperature survival of C. pisi pupae, however, was their autumn weight. The response was sigmoid and the 5%, 50% and 95% likelihoods for winter survival were at 157, 274 and 393 mg autumn pupal mass, respectively.This finding indicates that factors other than winter temperature, such as summer available thermal budget for larval growth, may be a limiting factor to the spread of C. pisi in Iceland. [ABSTRACT FROM AUTHOR]