Sources of variation in plant chemical diversity: Lessons from Malagasy Ficus

Plants produce a tremendous variety of secondary compounds that are crucial to interspecific and intraspecific interactions and for adaptation to environmental changes. This chemical diversity has been attributed to multiple factors, including interactions with herbivores or pollinators, tissue-specific needs, and evolutionary constraints. The interplay between a vast array of factors driving plant chemodiversity remains unclear, mainly because most studies have focused on a single organ-mostly leaves-or, when comparing different organs, have been limited to single taxa. Thus, the relationship between functional and phylogenetic factors remains unresolved. We use a model system of Ficus from Madagascar to examine the extent to which phytochemical diversity is shaped by tissue-specific function and the degree to which phylogenetic relatedness explains variation in fruit and leaf chemodiversity.

We applied an untargeted metabolomics approach to unripe fruits (the syconium, a hollow structure containing numerous small flowers) and leaves from eight species of wild figs (Ficus spp.) sampled in a tropical rainforest in Madagascar. We characterized their chemical profiles using ultra-performance liquid chromatography-mass spectrometry and reconstructed their phylogeny using six genetic markers to understand the patterns of chemodiversity.

Fruit and leaf metabolomes were more similar to the same organ in other species than to the other organs within the same species. There was a significant but moderate phylogenetic correlation in fruit and leaf chemodiversity.

Although phylogenetic relatedness influences plant chemodiversity in Malagasy figs, functional convergence of tissue-specific metabolites may be a major evolutionary driver.