Corolla herbivory, pollination success and fruit predation in complex flowers: an experimental study with Linaria lilacina (Scrophulariaceae)

Abstract

Background and aims: Herbivory on floral structures has been postulated to influence the evolution of floral traits in some plant species, and may also be an important factor influencing the occurrence and outcome of subsequent biotic interactions related to floral display. In particular, corolla herbivory may affect structures differentially involved in flower selection by pollinators and fruit predators (specifically, those ovopositing in ovaries prior to fruit development); hence floral herbivores may influence the relationships between these mutualistic and antagonistic agents.

Methods: The effects of corolla herbivory in Linaria lilacina (Scrophulariaceae), a plant species with complex flowers, were considered in relation to plant interactions with pollinators and fruit predators. Tests were made as to whether experimentally created differences in flower structure (resembling those occurring naturally) may translate into differences in reproductive output in terms of fruit or seed production.

Key results: Flowers with modified corollas, particularly those with lower lips removed, were less likely to be selected by pollinators than control flowers, and were less likely to be successfully visited and pollinated. As a consequence, fruit production was also less likely in these modified flowers. However, none of the experimental treatments affected the likelihood of visitation by fruit predators.

Conclusions: Since floral herbivory may affect pollinator visitation rates and reduce seed production, differences among plants in the proportion of flowers affected by herbivory and in the intensity of the damage inflicted on affected flowers may result in different opportunities for reproduction for plants in different seasons.

Fig. 1.

(A) Front and side view of a Linaria lilacina flower. (B) Schematic representation of the simulations of corolla herbivory. 1, upper lips removed (UP); 2, lower lips removed (LO); 3, both lips removed (BL).

Fig. 2.

(A) Mean number of flowers selected for a visitation attempt depending on the treatment (see Fig. 1 for abbreviations). All pollinators and populations pooled. Bars with different letters indicate significant differences. (B) Differences among pollinator groups and treatments in the likelihood that a visitation attempt resulted in a successful visitation. Both populations pooled. Data are means ±s.e.

Fig. 3.

Differences in handling time between flowers visited (V, successful visitation attempt) and not visited (NV, failed visitation attempt) for each pollinator group and treatment (see Fig. 1 for other abbreviations). Both populations pooled. Data are means±s.e.

Fig. 4.

Flower and plant visitation rates by each pollinator group depending on the treatment. See text for further considerations on these variables. Both populations pooled. Data are means±s.e. Horizontal lines indicate mean values across pollinator groups. See Fig. 1 for abbreviations.