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<p>Epiphytism evolved several times among plants, but among plant lineages, there is a high variability in the number of species that successfully conquered the canopy. Cactaceae have all the adaptations of water economy that should facilitate the evolution of epiphytes, but less than 7% of the cacti species are epiphytes. We performed a field experiment testing the effect of the substrate (forest soil, lava rock, canopy soil, and <i>Quercus rugosa</i> bark) on the germination, growth rate, and survival of five cacti species differing in their affinity to the epiphytic habit: two terrestrials (including one accidental epiphyte), one nomadic vine, and two holoepiphytes. Nutrient content differed between the substrates, the bark being the most rich. In vitro, seed germinations were high (&gt; 80% germination in vitro), but germination in field conditions was diminished by 47–91%, except for one holoepiphyte (<i>Disocactus speciosus</i>). Following their habit, the terrestrial species and the nomadic vine were more successful in forest and canopy soils, while holoepiphytes were generalists. When we secured the arrival of seeds to all the substrates, all cacti species showed some generalist use of the substrates, so the germination, early growth, and seedling survival don’t look like the main factors limiting these Cactaceae species to living in the canopy. Maybe Cactaceae lacks adaptations that increase the seedling performance in the canopy (e.g., taking water from the cloud, mycorrhizal fungus), limiting the evolution of epiphytic Cacti to humid environments only. Still, once the cacti seedlings develop succulent tissue, they can thrive in the canopy.</p>

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Does germination and early survival in different substrates filter the growing habit among terrestrial, nomadic vine, and epiphytic cacti? A field experiment

  • 期刊论文

  • 发表日期：

    2025年4月16日

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  • Paola Hilem Nava-Bernabé,
  • Susana Valencia-Diaz,
  • Victor H. Toledo-Hernández,
  • Alejandro Flores-Palacios

摘要

Epiphytism evolved several times among plants, but among plant lineages, there is a high variability in the number of species that successfully conquered the canopy. Cactaceae have all the adaptations of water economy that should facilitate the evolution of epiphytes, but less than 7% of the cacti species are epiphytes. We performed a field experiment testing the effect of the substrate (forest soil, lava rock, canopy soil, and Quercus rugosa bark) on the germination, growth rate, and survival of five cacti species differing in their affinity to the epiphytic habit: two terrestrials (including one accidental epiphyte), one nomadic vine, and two holoepiphytes. Nutrient content differed between the substrates, the bark being the most rich. In vitro, seed germinations were high (> 80% germination in vitro), but germination in field conditions was diminished by 47–91%, except for one holoepiphyte (Disocactus speciosus). Following their habit, the terrestrial species and the nomadic vine were more successful in forest and canopy soils, while holoepiphytes were generalists. When we secured the arrival of seeds to all the substrates, all cacti species showed some generalist use of the substrates, so the germination, early growth, and seedling survival don’t look like the main factors limiting these Cactaceae species to living in the canopy. Maybe Cactaceae lacks adaptations that increase the seedling performance in the canopy (e.g., taking water from the cloud, mycorrhizal fungus), limiting the evolution of epiphytic Cacti to humid environments only. Still, once the cacti seedlings develop succulent tissue, they can thrive in the canopy.