In this post, Zhe Chen—a postdoc at the CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences—share his recently published paper: “Red fruits exhibit lower colour diversity than red flowers as perceived by birds”. He discusses the patterns and potential mechanisms underlying the colour distinctions between red flowers and red fruits, and provides a glimpse into his personal experiences and journey towards ecological research.

A Chinese translation of this blogpost is available to read here!

About the paper

Colour plays a pivotal role in diverse plant-animal interactions. Both flowers and fruits utilize colour to attract pollinators and dispersers, while simultaneously discouraging potential threats like herbivores. Despite the relevance and parallels of these sequential ecological processes, the comparative evaluation of flower and fruit traits has been relatively scarce. The primary objective of our paper was to compare the colouration strategies between flowers (for pollination) and fruits (for seed dispersal).

Indeed, flower and fruit colour can be affected by various entangled biotic and abiotic factors, which complicates comparative analyses. In this study, we focused exclusively on red flowers and red fruits interacting with birds. This system intentionally excludes variations in colour across different shades, as well as differences in colour vision systems among distinct interacting animals. We conducted colour comparisons between red flowers and fruits based on direct reflectance spectra and animal colour vision models. Additionally, controlled experiments were carried out on pigeons to investigate the ecological function of red coloration.

About the research

Our findings contribute to a deeper understanding of the evolution of plant colours and the communication between plants and animals. We discovered that red flowers exhibit a higher degree of colour diversity compared to red fruits, particularly in terms of reflectance at shorter wavelengths. Furthermore, our research revealed that birds did not show a distinct colour preference among different shades of red at shorter wavelengths, although they were capable of discriminating between them. This study underscores the profound influence of evolutionary history on the coloration of flowers and fruits, warranting increased attention in future studies.

A substantial challenge in our research was manipulating pigeons to make choices. Initially, the pigeons displayed a directional bias when we presented two options side by side. Individual pigeons consistently approached the left one first and then moved to the right, or vice versa. Despite numerous adjustments, such as altering the layout of the arena, modifying the distances between choices, and implementing periods of fasting before experiments, the pigeons simply didn’t make a choice. This period was marked by long, arduous efforts without visible progress. However, a breakthrough came to me one day—I realized that pigeons perceive their surroundings differently from humans or certain insects, with their eyes oriented laterally rather than forward. With this insight, I reconfigured the experimental setup, arranging the choices in a Y-shaped formation, so that the two options were positioned in different lateral directions. This adjustment yielded success! The pigeons hesitated this time, frequently turning their heads left and right for observation before making a choice. It was a moment of great satisfaction, as I relished in the satisfaction of overcoming an experimental challenge.

About the Author

I embarked on my research journey into plant colour in 2014, during my time as a master’s candidate. My initial project focused on the evolutionary patterns of red flowers, a venture that provided me with valuable training in plant-animal communication, animal colour perception, and colour vision models. Subsequently, in 2017, I commenced my doctoral project centred around the flower trait evolution of Brandisia (Orobanchaceae). This endeavour deepened my understanding of phylogeny and biogeography, offering me a more comprehensive perspective on evolutionary history. In 2020, I started this study on red flowers and red fruits, integrating ecology and evolutionary history. Exploring plant coloration continues to captivate me as it represents a progressive step towards comprehending the vivid tapestry of the natural world. It allows me to unravel the wisdom of plants and decipher the intriguing interactions between plants and animals. Furthermore, conducting ecological research provides me with the opportunity to immerse myself in diverse plant species and relish in the breathtaking landscapes, ultimately granting me a sense of tranquillity.

Enjoyed the blogpost? Read the research here!