Adaptation of a generalist moth, Operophtera brumata, to variable budburst phenology of host plants

The adaptation of three allopatric populations of a generalist moth, Operophtera brumata (L.), on two tree species, Prunus padus (L.) and Quercus robur (L.) which represent the extremes of the timing of budburst in spring, was studied in Finland and Sweden. The synchrony of the hatching and budbursting was monitored, and its importance to dispersal and growth of larvae was assessed by rearing cohorts of larvae, whose hatching dates were manipulated, on both hosts. In addition, the realised heritability of the hatching time was estimated. Experimental populations hatched in approximate synchrony with the budburst of their original host species. As a result of the manipulation of the hatching dates of larvae, the growth rates of larvae decreased and the dispersal rates increased on both hosts in relation to the ageing of foliage. The realised heritability of hatching times was rather high (0.63). There were fewer differences in the host use efficiency and behaviour of the experimental populations than in the hatching phenology. The synchrony of hatching with the budburst of the local dominant host plant is probably a result of stabilising selection.