Plant reproduction typically involves close relationships with animals that help them, either by aiding in their pollination or seed dispersal. For example, during spring, one might see a new flush of flowers being visited by various kinds of insects and other pollinators. Those flowers, once pollinated, will develop into fruits that could be dispersed by different animals, such as birds and small mammals. However, what if I told you that some plants have evolved with a less conventional, yet dramatic approach? Would you believe me if I told you that this approach involves fire and a very specific set of dispersers?
This is the story of Apodolirion buchananii, a plant from eastern South Africa and Eswatini that produces nectarless, yet bright, fragrant flowers right after natural fire events, even before the plant has had time to produce leaves again. Unlike most plants we are all familiar with, this species’ ovaries—the structures that develop into fruits after pollination—are subterranean, meaning the fruit remains underground for six months until it reaches maturity. As surprising as this may seem, despite these fascinating traits, the plant’s pollination and seed dispersal ecology remain shrouded in mystery. For instance, previous studies and observations of closely related species have been full of uncertainties and contradictions, leaving us with more questions than answers.
In a study published in the American Journal of Botany, researchers Ian Kiepiel and Steven D. Johnson monitored natural populations in two nature reserves in South Africa to observe the flowers and their pollinators over several weeks, recording the types of insects that visited the flowers. The authors also analyzed the flowers’ visual characteristics and the compounds present in the fragrance of their flowers, fruits, and seeds. They then conducted field experiments with scent traps to evaluate the role of such scent compounds in attracting pollinators and dispersers. Moreover, they employed camera traps to identify the animals responsible for seed dispersal.
The flowers of Apodolirion buchananii might be nectarless, but the study by Kiepel and Johnson shows that their strong scent was enough to attract more than 107 insects during the observation, with over 70% of the visits being by various bee species. Bees were shown to be highly effective pollinators, as they carried much more pollen than other insects like flies or butterflies. These observations were consistent with the authors’ scent analysis, as around half of the flower scent is made up of phenylacetaldehyde, an aromatic compound known to be an excellent bee attractant—something that was also confirmed with the scent traps placed in the field by the researchers.
When it comes to seed dispersal, the authors were surprised to find that ants were the main dispersers of Apodolirion buchananii seeds. Interestingly, ants were particularly attracted to seeds right after fruit ripening, likely because the scent mimics that produced by ant larvae, suggesting that the ants, rather than acting altruistically, actively collect these seeds, thinking they are rescuing their larvae.
Altogether, this fascinating study leaves us with a detailed perspective on Apodolirion buchananii‘s reproductive ecology, clearing up several long-standing doubts along the way. Moreover, the research shows the importance of timing in this plant’s reproduction. On one hand, producing bright flowers after a fire gives this plant an opportunity to stand out in an otherwise desolate landscape and ensure visits by several bees lured by their strong scent. This is notably important, considering that the authors observed that these plants are self-incompatible, meaning they depend on exchanging pollen between flowers to produce fruits. On the other hand, keeping their fruits underground until they are ripe ensures they remain protected until seeds are mature enough to be dispersed. As a result, this research not only sheds light on a unique plant’s life cycle but also opens new doors for understanding how fire, bees, and ants work together in the natural world, especially in ecosystems prone to fire. Perhaps these ecosystems still harbour unique dynamics between plants and animals that we can’t yet imagine.
READ THE ARTICLE:
Kiepiel, I. and Johnson, S.D., 2024. Scent‐mediated bee pollination and myrmecochory in an enigmatic geophyte with pyrogenic flowering and subterranean development of fleshy fruits. American Journal of Botany, 111(11), p.e16421. https://doi.org/10.1002/ajb2.16421
Victor H. D. Silva
Victor H. D. Silva is a biologist passionate about the processes that shape interactions between plants and pollinators. He is currently focused on understanding how plant-pollinator interactions are influenced by urbanisation and how to make urban green areas more pollinator-friendly. For more information, follow him on ResearchGate as Victor H. D. Silva.
Portuguese translation by Victor H. D. Silva.
Cover picture: Apodolirion buchananii in South Africa. Photo by Jimmy Whatmore (Wikimedia Commons).
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