An international study involving Alexandra Rodríguez, Helena Castro and Jorge Durán, researchers at the Centre for Functional Ecology (CFE) at the Faculty of Science and Technology of the University of Coimbra (FCTUC), shows that plants in dry areas adopt many different adaptation strategies and that, surprisingly, this diversity increases with levels of aridity.
Published in Nature, this study involved 120 scientists from 27 countries with the aim of understanding how plants found in drylands have adapted to these extreme habitats. Over the course of eight years, scientists collected samples from several hundred selected dryland plots across several continents.
According to Helena Castro, «the isolation of these plants in more arid zones appears to have reduced competition between species, allowing them to express a diversity of forms and functions that is globally unique, exhibiting twice the diversity found in more temperate zones».
“This study sheds new light on our understanding of plant architecture, plant adaptation to extreme habitats, historical plant colonization of terrestrial environments, and the ability of plants to respond to current global changes,” says Alexandra Rodríguez.
Scientists collected and processed samples from 301 plant species found in 326 representative plots from all continents (except Antarctica) to characterize the functional diversity of the zones, generating a total of 1 complete sets of trait observations for analysis.
Initially, it was thought that aridity would reduce plant diversity through selection, leaving only those species capable of tolerating extreme water scarcity and heat stress. However, experts have discovered that in the driest parts of the world, plants exhibit a wide range of adaptation strategies.
“For example, some plants have developed high levels of calcium, strengthening their cell walls as a protection against desiccation. Others contain high concentrations of salt, reducing transpiration. Although fewer species are observed at a local scale compared to other regions of the planet, plants in arid areas exhibit an extraordinary diversity of shapes, sizes and functions,” says Jorge Durán.
This increase in trait diversity occurs abruptly at the point where rainfall decreases below the annual threshold of 400 mm. This is also the threshold for a pronounced decline in vegetation cover and the emergence of large areas of bare soil. To explain this phenomenon, the authors of the study suggest that the loss of vegetation cover leads to the plant solitude syndrome, in which increased isolation and reduced competition for resources produce high degrees of trait uniqueness and functional diversity that are globally exceptional.
“This study reveals the importance of drylands as a global reservoir of plant functional diversity, providing a new lens through which to view plant architecture, plant adaptation to extreme habitats, historical plant colonization of terrestrial environments, and the ability of plants to respond to current global changes,” the experts conclude.
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