In addition, the Atacama hosts one of the most breathtaking natural phenomena once every five to ten years on average, from mid-September to mid-November: the “desierto florido” (literally “flowering desert”).
Earlier this year, following heavy rains, one of these mass blooms, currently occurring in the northern Atacama, has been frequently covered in media from all over the world.
But what physiological and evolutionary processes enable the enormous range of flower colors, shapes and patterns in desiertos floridos? And how do pollinators, primarily proboscis such as the solitary wasps and bees of the Atacama, who benefit from this visual luxury, perceive all this diversity? A recent study published in the journal Frontiers in Ecology and Evolution addresses this issue.
“Our goal was to shed light on the ecological and evolutionary mechanisms that drive biodiversity in extreme environments such as the Atacama Desert,” said first author Dr. Jaime Martinez-Harmsresearcher at the Institute of Agricultural Research in La Cruz, Chile.
“Here we show that the flowers of Cistanthe longiscapa, a species representative of the desiertos floridos in the Atacama desert, vary widely in color and pattern for pollinators. This variation is probably due to different so-called ‘betalain’ pigments. flower petals.”
In late 2021, Martnez-Harms and colleagues studied the desierto Florido event near the northern Chilean city of Caldera. Although it was smaller than the current event, it was clearly seen by satellites. The dominant species was the annual plant C. longiscapa (family Montiaceae), which flowered in two separate piers tens of kilometers apart and reached a height of 20 cm. To the human eye, these patches consisted exclusively of purple and yellow flowers. Between them grew numerous intermediate flowers of the same species—reddish, pink, and white—providing strong evidence that the purple and yellow morphs are heritable variants that can interbreed.
Visualizing flowers as insects see them
Insects, with different eyes and sensitivities, see the world in a completely different way than we do. For example, most hymenopterans have three types of photoreceptors that are maximally sensitive to UV radiation, blue and green. Martinez-Harms et al. used cameras and spectrometers sensitive to visible light and UV to measure the reflection, absorption and transmission of different wavelengths from a total of 110 purple, yellow, red, pink and white C. longiscapa flower petals. This allowed them to produce composite images of these variations as seen by many pollinator species.
Diversity hidden from people’s eyes
The results show that precisely within this single plant species, the observable diversity of pollinators was greater than ours. For example, hymenopterans, just like us, can easily distinguish red, purple, white, and yellow variations. But they can also distinguish flowers with high and low UV reflectance among yellow and purple flowers. The UV eye pattern in the heart of some flowers that guides pollinators to nectar and pollen is invisible to us.
The exceptions are the UV-reflective pink and reddish C. longiscapa, which are quite different to the human eye, but probably look similar to hymenopterans.
This visual diversity of C. longiscapa flowers is probably mainly due to the differences between the betalains – the yellow, orange and purple pigments that are a characteristic feature of the plant order Caryophyllales, to which cattails belong. Betalains don’t just give flowers their colors: they also protect against drought, salt stress and damage caused by reactive oxygen radicals under environmental stress – very useful in deserts.
Pollinators guide the selection of new variants
The authors suggested that the observed diversity in C. longiscapa flowers is due to variations in pollinator sensitivity and preference for different colors and patterns—a current evolutionary experiment that goes largely unnoticed by humans.
“The great variation in flower colors of C. longiscapa can be explained if different species of pollinating insects, because they prefer certain flower colors and patterns, can cause these variations to reproduce in isolation from other individuals of the same plant species. This process can eventually lead to the emergence of new races or species,” Martinez- Harms said.
“In our next studies, we will further investigate the chemical identity and biological synthesis pathways of betalains and other flower pigments, as well as their relationship to traits such as the scents produced by flowers. This should help us understand their role in shaping the interactions between plants and their pollinators and the tolerance of plants to biotic and abiotic stressors in varying climates.” , said Martinez-Harms.
Source: The Nordic Page