The phenological window of opportunity for early‐season birch sawflies

摘要: 1. The phenological window of opportunity hypothesis posits that an insect herbivore cannot survive outside a specific leaf age interval its host plant. 2. Previous studies have shown mountain birch displays extensive seasonal changes in biochemical characteristics. Young, expanding leaves are full water and amino acids but they also contain large amounts protein-precipitating gallotannins as well flavonoid-glycosides. Concentrations these compounds decline during growth whereas concentrations sugars proanthocyanidins toughness increase. 3. Adult sawflies hatch early summer oviposit on growing leaves, which compels larvae to feed already developed. purpose this study was test whether were younger biochemically different from the available under natural conditions within for two early-season sawfly species, Amauronematus amplus Konow Pristiphora alpestris (Konow). 4. survived better developed faster, P. alpestris faster became bigger, atypically young compared with reared encountered normally. Therefore, species can exploit putative nutritional superiority very probably outweighs potential impact new set secondary metabolites offered them. In conclusion, consumed rarely by their opportunity, even though timing life cycles constrains utilisation.