Flower Size as an Honest Signal in Royal Irises (Iris Section Oncocyclus, Iridaceae)

Abstract

Flower traits, such as flower size or color changes, can act as honest signals indicating greater rewards such as nectar; however, nothing is known about shelter-rewarding systems. Large flowers of Royal irises offer overnight shelter as a reward to Eucera bees. A black patch might signal the entrance to the tunnel (shelter) and, together with the flower size, these might act as honest signals. We hypothesize that larger flowers and black patches indicate larger tunnels, and larger tunnels will increase pollinator visits, enhancing the plants’ reproductive success. We measured seven species in a controlled environment and two species from three natural populations varying in flower size. Fruit and seed sets were assessed in these natural populations. We found a positive correlation between the flower, patch size, and tunnel volume, suggesting that the flowers and patch size act as honest signals, both under controlled conditions and in the wild. However, in natural populations, this positive relationship and its effect on fitness was population-specific. Flower size increased the fitness in YER I. petrana, and interactions between flower/patch size and tunnel size increased the fitness in YER and I. atropurpurea NET populations. This suggests that the honesty of the signal is positively selected in these two populations. This study supports the hypothesis that pollinator-mediated selection leads to the honest signaling of flower advertisement.

Visual-, Olfactory-, and Nectar-Taste-Based Flower Aposematism

“…Colorful flowers are the most common and best-known visual characteristic used by plants to communicate with animals. The most common and most studied aspect of this visual communication of flowers with potential pollinators is their attraction (e.g., [1][2][3][4][5][6][7]). Another specific aspect of color-related visual flower-pollinator interactions is a change in flower color as a signal, which shows that specific flowers are already pollinated [8][9][10].…”

Introduction to the Special Issue of Plants on “Advances in Plant Reproductive Ecology and Conservation Biology”

“…(Ebenaceae), and these authors not only recognized vestigial sexual organs in the unisexual flowers but also identified some plants as being sexually leaky, with plants that develop staminate flowers also producing some fruits. In multiple species of Iris , Lozada-Gobilard et al [ 15 ] investigated the role of visual floral cues as honest signals. The researchers found evidence of honest signaling, across multiple species of Iris , in a garden setting, but the effect was population-specific in natural environments, with abiotic factors possibly playing a role.…”

“…(Ebenaceae), and these authors not only recognized vestigial sexual organs in the unisexual flowers but also identified some plants as being sexually leaky, with plants that develop staminate flowers also producing some fruits. In multiple species of Iris, Lozada-Gobilard et al [15] investigated the role of visual floral cues as honest signals.…”