Diary Razafimandimby

Wild figs ( Ficus spp.) play a central role in tropical ecosystems by providing food to a wide range of frugivores, often due to high fruit yields and a presumed lack of distinct phenological patterns. This assumption is particularly important in Madagascar, where figs may represent a year-round resource for the island’s unique frugivore community. However, evidence for truly aseasonal fruiting remains limited, and previous studies have rarely distinguished between ripe and unripe figs, potentially overestimating resource availability. We investigated Ficus phenology in two contrasting forest types, the wet forests of Andasibe-Analamazaotra and the dry forests of Ankarafantsika to determine whether (1) fig production exhibits distinct temporal patterns and (2) these patterns differ between habitats. Over three years (2021–2024), we monitored 94 individual trees representing 11 species and recorded fig presence and ripeness stage. Fruit production occurred throughout the year, and circular statistical analyses detect no significant seasonal peaks in either unripe or ripe figs. Similarly, despite strong environmental contrasts, ripe fig fruiting patterns did not differ significantly between sites, although a difference was detected for unripe figs. These results suggest that Malagasy Ficus do not exhibit distinct phenological patterns at the species or community level, with fruit production broadly aseasonal across habitats. This year-round pattern, including the recurrent ripe fig availability, suggests that Ficus may provide a relatively continuous food resource for frugivores, particularly during periods of fruit scarcity, while highlighting the need to understand the ecological significance of unripe figs.

Fleshy fruits have evolved diverse traits to attract seed dispersers in response to frugivore behavior and sensory capacities. Fruit scent has been suggested to signal ripeness and nutritional quality, yet the volatile components involved and the information they convey remain poorly understood. It is unknown which information is encoded in fruit scent, whether plants actively synthesize these signals, and thus whether scent constitutes an evolved communication system shaping seed-dispersal interactions. Aliphatic esters, chemicals whose odor is often described as “fruity,” are abundant in some ripe fruits, especially those dispersed by animals which tend to rely on their sense of smell for fruit selection. Moreover, they have been argued to be associated with sugar content, potentially rendering them an honest signal and hence a hotspot of animal-plant chemical communication. We investigated whether aliphatic esters indicate fruit quality honestly and represent an adaptive trait shaped by disperser identity. Using 13 fig species ( Ficus spp.; Moraceae) in Madagascar, we quantified seed dispersal by multiple animals using a quantitative ecological network. We then quantified chemical signals and nutritional rewards using thermal desorption gas chromatography-mass spectrometry (TD-GCMS) and high-performance liquid chromatography (HPLC), and used genome-guided transcriptome assembly to identify the candidate genes responsible for ester signaling. Our results show that (a) aliphatic esters occur more frequently in species dispersed primarily by olfactory-oriented mammals than in those dispersed by visually oriented birds; (b) ester abundance correlates positively with soluble sugar across species only in mammal-dispersed species, indicating an honest signal that is activated only when ecologically relevant; and (c) putative AAT gene revealing elevated expression associated with the increased abundance of aliphatic esters, sugars in single mammal-dispersed taxon. Together, these findings support the hypothesis that fruits have evolved to utilize the biochemical link between esters (signals) and sugars (rewards) to provide honest signals to seed dispersers. Significance Statement: Fruit–frugivore communication is a critical component of ecological systems as it allows animals to find and identify ripe fruit, thus facilitating seed dispersal, plant reproduction, forest regeneration, and animal community maintenance. Chemical communication via fruit scent remains underexplored, particularly regarding the information encoded, active signal synthesis, and adaptive significance. Using a model system of wild figs from Madagascar, our study suggests that fruits have evolved to utilize aliphatic esters, a group of chemicals commonly described as “fruity” by human observers, to signal sugar levels to seed-dispersing animals. In species that rely on lemurs, which tend to rely strongly on their sense of smell, ester levels were higher than in bird-dispersed species, where visual signals are more prominent. Further, in lemur-dispersed species ester levels were correlated with sugar, indicating that they are reliably signaling fruit quality. Linking these patterns to elevated expression of the gene mediating ester biosynthesis, we also identify a molecular mechanism potentially under selection. These findings establish fruit scent as an adaptive communication system and reveal how plant chemicals evolve under mammalian selection.

Premise: 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.Methods: 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.Results: 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.Conclusions: Although phylogenetic relatedness influences plant chemodiversity in Malagasy figs, functional convergence of tissue‐specific metabolites may be a major evolutionary driver.