Differences in insect species richness and faunal composition of birch seedlings, saplings and trees: the importance of plant architecture

Abstract

Abstract. 1. Data are presented on the species richness and faunal composition of herbivorous insects on birch seedlings, saplings and trees at one site in Northern England.2. Species richness of insect herbivores in equal‐sized samples from birch seedlings and trees was similar through most of the season.3. Effects of plant architecture were confined to the first sampling date, when seedling faunas were species poor compared with trees – possibly due to safe overwintering sites on the extensive bark, twigs and buds of trees.4. The faunal composition of birch seedlings, saplings and trees was also similar. Out of a total of 112 recorded species of herbivores, only one aphid species was confined to seedlings.5. Similarly, no evidence for clear‐cut vertical stratification of insects within trees was found.6. Species turnover as host plants mature (‘horizontal’ stratification) and vertical stratification within trees add little to the high overall species richness of birch‐feeding insects in Britain, contrary to the predictions of Lawton (1983).