The research explores the diversity of colors in desert blooms from the human eye and from pollinators

Thanks to the rains that fell this winter, the Atacama Desert has become a real spectacle, with multiple and colorful flowers that have grown in the center of this particular territory, the second driest on the planet, after the polar ecosystems.

Whenever this sporadic phenomenon occurs, there are many and varied species that appear, including Cistanthe longiscapa, the same one that has generated great curiosity in a group of Chilean researchers, who in October 2021 observed how these flowers had strange new colors.

In one sector north of the Caldera, this native plant, popularly known as guanaco foot, had grown into several patches of purple and yellow flowers, among which there were also numerous intermediate shades: reddish, pink and white.

Following the discovery, scientists Jaime Martínez-Harms, of the Institute for Agricultural Research, INIA, and Pablo Guerrero, researcher at the Institute of Ecology and Biodiversity (IEB) and the University of Concepción, studied the ecological and evolutionary mechanisms that have generated this diversity of colors and visual patterns in an extreme environment such as the Atacama Desert and how pollinators perceive this variability.

The work, recently published in the scientific journal Frontiers in Ecology and Evolution, also saw the participation of María José Martínez-Harms, IEB researcher, among other Chilean scientists, scientists from the Netherlands and New Zealand.

Study the diversity of colors

“At this spot near the Caldera I was struck by the fact that there were two very distinctive separate patches of flowers, one yellow and one pink, and that in the areas where these met there was a greater abundance of colors not common to Cistanthe. Hence the idea of ​​characterizing the colors of these flowers with a camera modified to broaden its sensitivity and a spectrometer. When we started evaluating colors, we saw that in addition to differences in the range of colors visible to humans, there were differences in the ultraviolet range. And this is very interesting, because pollinators, generally birds and insects, unlike us, perceive colors in that range of the light spectrum,” explains Jaime Martínez-Harms.

Pablo Guerrero explains that polymorphisms in nature, that is, the differences in physical characteristics between individuals of the same species, are the raw material of evolution.

“Variability within each species is a fundamental dimension of biodiversity. These polymorphisms in plants occur due to the interaction with their pollinators”, underlines the researcher from the IEB and the University of Concepción.

To understand these interactions, the research also incorporated an approach to landscape ecology, led by María José Martínez-Harms, director of the Laboratory for Ecosystem Conservation and Human Welfare at the IEB.

“My role was to address this color variability by considering the scale of the landscape, which can have an impact on the resilience and adaptive capacity of ecosystems,” explains the researcher.

The researchers point out that these color changes represent historical processes and in this context, what we see today is the result of changes that could have occurred tens, hundreds or thousands of years ago, giving rise to landforms that can sometimes be highly specialized for certain pollinators of the flowering desert.

Watching the desert as a pollinator

What results did you get from this particular visual spectacle and from field and laboratory analyses? How do pollinators, mainly solitary wasps and bees, perceive the colors of Cistanthe flowers and their differences?

According to the study, this variability of colors in guanaco paws is due to the generation of different pigments in the flower petals, called “betalains”, which in turn are known to protect plants from drought, salt stress and other environmental factors. .

This colorful desert feast is perceived differently by humans and pollinators, as pollinators can see a different range of colors than humans.

To understand this, the study looked at flowers from the perspective of a pollinator, specifically the honey bee. For the study, the scientists looked at the color perception of bees, which have three types of light receptors in their eyes, sensitive to the ultraviolet, blue and green ranges of light, respectively. The results show that these insects are able to perceive a greater diversity of colors in this plant species than humans, which have receptors sensitive to blue, green and red, but not to ultraviolet.

In the case of these flowers, Hymenoptera, just like us, can easily distinguish between red, pink, white and yellow variants. But they can also distinguish between flowers that reflect ultraviolet light, from those that have little or no UV, variants found in yellow and pink flowers. Similarly, in some flowers there is what is called a “bullseye” pattern, a kind of ultraviolet sign that guides pollinators towards nectar and pollen, invisible to us.

According to the authors, the chromatic variation of these flowers would also be related to the fact that different pollinating insects, through their preference for flowers with particular patterns of color and shape, would encourage these variants to be reproductively isolated from other individuals of the same species. species of plants, a process that could give rise to new races or even species.

“We believe that this color variability may help ensure the reproduction of these plants, considering that desert flowering events are short and sporadic. This variability is very important because it tells us that to ensure the conservation of these species it is important not only to look at the species as a whole, but also to protect each of its variants,” Jaime Martínez-Harms points out.

support conservation

Both Pablo Guerrero and María José Martínez explain that understanding these interactions that occur in the Atacama Desert, addressing perception and ecology together, is important to advance not only in the generation of scientific knowledge, but also in the conservation of this particular ecosystem.

“The Atacama Desert is a true research laboratory on our biodiversity, and hence the importance of developing these studies. It’s very interesting to communicate to society that we don’t all perceive the world the same way, as we do with some pollinators. It is essential to underline that initiatives such as the creation of the “Parco Nazionale del Desierto Florido” can be very relevant to conserve this heritage of biodiversity, which has an uncertain future due to the impacts of climate change, land use change, pollution and other human actions… We must support the conservation actions of our biodiversity, since it not only has a value in itself, but it is also an insurance of life and resilience for people and nature”, explains María José Martinez.

Pablo Guerrero underlines the importance of the desert and its biodiversity, visible and invisible.

“Nature brings many benefits to people. However, much biodiversity is not always visible to our eyes. Nocturnal or scarce species can remain hidden underground for years, in the form of seeds. Therefore, the conservation of these ecosystems, beyond the obvious, has enormous ecological and social value, which we should further promote through science and various environmental education initiatives,” concludes the IEB scientist.

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