The unkindest cut?
In
discussion of plant–animal relations, a number of topics come readily to mind.
One is pollination and another is herbivory, where the focus is most often on
leaves and shoots. Further, the interaction between these two may be important,
as shown by Sánchez-Lafuente at Seville,
Spain (pp.
355–364). The author worked with Linaria linacina, a member of the
Scrophulariaceae with complex flowers, and asked whether flower herbivory
affects pollination. This, in turn, raises the question of which components of
floral morphology are important in attracting pollinators. The author observed
floral herbivory in the field and then mimicked the action of herbivores by
removing parts of the corolla. From his extensive study, we focus here on just
three features. First, removal of the upper lip of the corolla led to a only a slight reduction in the frequency of visitation by
pollinators, whereas removal of the lower lip caused nearly a 50 % reduction in
the number of visits; removing both lips had a similar effect to removing the
lower lip. The lower lip of the corolla is thus important in attracting
pollinators. Secondly, in terms of success of those visits that did occur,
results varied between the three main pollinating species. However, in general,
removal of either lip or both reduced markedly the likelihood that a visit
would be successful. Finally, and as might be expected, different treatments
did lead to differences in fruit set. Plants in which the upper lip was removed
showed a similar level of fruit set to controls. Removal of just the lower lip
or of both lips reduced significantly the proportion of flowers that set fruit,
but the number of seeds per fruit was not affected. This study, especially when
the author’s results on fruit predation are also considered, gives an insight
into the complex web of biotic factors that affect plant reproduction.
Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk
