The wide variety of flower colours, sizes, and shapes may be both fascinating and familiar to those of us who are interested in nature. But while we might be aware that pollinators like bees and birds help shape these traits, have we thought about how climate influences their evolution? A new study published in the Annals of Botany Special Issue on Plant Reproduction in a Changing Global Environment, found both pollinators and climate contribute to the evolution of floral characteristics in Rhododendron genus.
Basnett et al. examined 21 Rhododendron species across two continents: North America’s Appalachian Mountains and the Himalayas in Asia. They measured some floral traits, including corolla length, nectar volume, and nectar concentration. At the same time, they recorded floral visitors, identifying four main groups: birds, bees, butterflies, and flies.
The study revealed interesting differences in both pollinator communities and floral morphology between the two regions. Asian Rhododendron species had visits from a wider range of pollinators, including birds, bees, and flies. In contrast, North American species were mainly visited by bees and butterflies. This geographical variation in pollinators appears to have shaped floral traits.
Nectar turned out to be a key feature influenced by the type of pollinator visiting each species. Flowers visited by birds tended to produce larger volumes of dilute nectar, which satisfies the high energy demands of these visitors. On the contrary, flowers pollinated by insects offered smaller quantities of more concentrated nectar.
Interestingly, the study also found a strong evolutionary relationship for nectar concentration and corolla length. This suggests that these have been part of Rhododendrons for a long time and have been passed down through generations.
In the Himalayas, the researchers found evidence that climate also plays a significant role in shaping nectar traits, which at the same time presented interactions with pollinator identity. This complex relationship between climate and pollinators highlights the challenges faced by plants in a changing world.
Climatic variables such as temperature seasonality and mean annual air temperature also appeared to affect floral traits and interact with pollinator identity to explain floral trait variation, building on the evidence that floral trait variation is driven by contributions (and interactions) of both biotic and abiotic variables. These last results suggest that changes in climate have the power to affect floral traits important for pollination interactions in this plant group, with potential yet unknown effects on the ability of the plants to sustain fitness in changing climatic conditions.
Understanding how climate drives variation in floral traits is crucial for protecting plant-pollinator interactions in the face of global climate change. As temperatures rise and weather patterns shift, the balance between plants and their pollinators could be disrupted, potentially leading to wider effects throughout ecosystems.
READ THE ARTICLE:
Basnett S., Krpan J. and Espíndola A. (2025) Annals of Botany. Floral traits and their connection with pollinators and climate. Available at: https://doi.org/10.1093/aob/mcae046
The post The Role of Pollinators and Climate in Shaping Floral Characteristics appeared first on Botany One.
