Fig. 8. The evolutionary dynamics of tillandsioids.

About 11.3 Mya in the Andes, the trichomes of the tillandsioid ancestor acquired the function of absorption and diverged from bromeliads with well-developed root systems. Since then, without needs of reliance on soil, tillandsioids could escape intense ground-level competition for space, allowing them to occupy new ecological niches. Approximately 2.6 million years later, tank-forming tillandsioids emerged with the tightly folded leaf rosettes forming tanks that collected and stored rainwater. The root absorption function became obsolete, leading to the gradual loss of genes controlling root hair formation,root geotropism and hydrotropism. Concurrently, many genes involved in SCWs synthesis were highly expressed in roots, enhancing their mechanical support as ‘holdfast’ structures. Around 6 million years ago, the Andes underwent rapid uplift, influencing regional climate and accelerating the genome expansion and evolution of tillandsioids. By approximately 5.1 Mya, another type of tillandsioid emerged with well adaptation to more arid habitats. These plants developed leaves densely covered with trichomes, protecting them from sunlight, reducing water evaporation, and mitigating high temperatures. They also formed a symbiotic relationship with phyllosphere bacteria, which provided nutrients, enabling them to thrive as true ‘air plants’ in harsh environments such as deserts.