Autumn colouration and herbivore resistance in mountain birch (Betula pubescens)

We explored Hamilton and Brown's autumn signalling hypothesis in mountain birch (Betula pubescens). As predicted by the hypothesis, early autumn colour change (i.e. high degree of autumn colouration in September) was negatively correlated with insect damage the following season. Furthermore, as expected, indices of physiological stress (i.e. leaf fluctuating asymmetry) and reproductive investment (i.e. catkin production) were positively correlated with insect damage the following season. Indirectly, we also found support for the idea that the proposed handicap signal (i.e. early autumn senescence) might be associated with an honesty ensuring cost in terms of lost primary production. Further work is, however, required to determine whether the link between autumn colours and insect damage observed in this study is causal.