Evolutionary and environmental drivers of dry-season deciduousness in a legume genus.
Cássia-Silva C, Cavender-Bares J, Simon MF, Herrera-Alsina L, Marcilio-Silva V
Climate Adaptation
Mimosa shrubs you might spot along roadsides or in dry gardens — those feathery-leaved plants that fold up when touched — are living examples of an ancient survival playbook written millions of years before today's droughts began.
Some tropical plants shed their leaves in the dry season, much like temperate trees shed leaves in winter, to avoid losing water. Researchers looked at mimosas — a huge, diverse group of plants — to figure out why some are leaf-droppers and others stay green all year. They discovered that while dryness in the air does push plants toward dropping leaves, the biggest factor is simply what species the plant is and who its ancestors were, not just where it grows today.
Key Findings
Switches from evergreen to deciduous habit were more common before about 7 million years ago; after that, the reverse transition and faster diversification of evergreen lineages took over.
Vapor pressure deficit (atmospheric dryness) was the strongest environmental predictor of dry-season deciduousness, with deciduous lineages evolving faster along that gradient.
Most variation in leaf habit was explained by species identity and shared ancestry (phylogeny), not by environmental conditions alone.
chevron_right Technical Summary
Scientists studied why some tropical plants drop their leaves during dry seasons rather than keeping them year-round. Using the mimosa plant family as a test case, they found that this drought-dodging strategy is shaped more by a plant's species identity and evolutionary heritage than by the local climate alone.
Abstract Preview
Leaf deciduousness is a key drought-avoidance strategy in tropical flora, reducing water loss during seasonal dry periods. While winter-deciduousness in temperate regions is well-understood, the ev...
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Mimosa is a genus of about 600 species of herbs and shrubs, in the mimosoid clade of the legume family Fabaceae. Species are native to the Americas, from North Dakota to northern Argentina, and to eastern Africa as well as the Indian subcontinent and Indochina. The generic name is derived from th...