M2 Internship
n°2 | 2020

Keywords invasive plants, honey bee, vision, color detection, color discrimination

From July to November 2020, I worked at the Research Center on Animal Cognition (CRCA) in Toulouse, France, under the supervision of Sylvie Guillerme and Martin Giurfa. Despite the constraints of the COVID‑19 pandemic, we were fortunate to conduct fieldwork in the Pyrenees, where we measured the spectral reflectance of flowers. We then used a perceptual approach based on the neural mechanisms of bee vision to compare different properties of local flowers with invasive flowers. Our results suggested two main strategies for invasive flowers: either resembling local species to blend into the floral community and encourage generalization by bees, or standing out visually to potentially attract more pollinators. In this work, we focused on visual cues, but invasive plants use multiple sensory dimensions, so this work is now followed by the thesis of Frank Weber

Resume of our project

Invasive plants represent a significant global challenge as they compete with native plants for limited resources such as space, nutrients and pollinators. Here, we focused on four invasive species that are widely spread in the French Pyrenees, Buddleja davidii, Reynoutria japonica, Spiraea japonica and Impatiens glandulifera, and analyzed their visual advertisement signals with respect to those displayed by their surrounding native species using a perceptual approach based on the neural mechanisms of bee vision given that bees are regular pollinators of these plants. We collected 543 spectral reflections from the 4 invasive species, and 66 native species and estimated achromatic and chromatic similarities to the bee eye.

R. japonica, S. japonica and B. davidii were inconspicuous against the foliage background and could be hardly discriminated in terms of color from their surrounding native plants. These characteristics promote generalization, potentially attracting pollinators foraging on similar native species. Two morphs of I. glandulifera were both highly salient in chromatic and achromatic terms and different from their surrounding native species. This distinctive identity facilitates detection and learning in association with rich nectar. While visual signals are not the only sensory cue accounting for invasive-plant success, our study reveals new elements for understanding biological invasion processes from the perspective of pollinator perceptual processes.

This work led to this paper: (Dessart et al., 2024)