Browsing by Author "Kulkarni, Manasa"

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Developing together: The elementome and biogeochemical niche of the mutualistic occupants of a fig microcosm
(2026) Kulkarni, Manasa; Naik, Nehal Vijay; Vadassery, Jyothilakshmi; Borges, Renee M.
In brood-site pollination mutualisms, where flowers provide nutrition and shelter to pollinator offspring in exchange for pollination, resource allocation to inflorescences is directly related to plant and pollinator fitness. We determine resource allocation to components of an enclosed monoecious Ficus inflorescence or syconium that, besides seeds, also houses and provides nutrition to pollinator wasp offspring, each developing within individual uniovulate galled flowers. Besides biomass, we determine elemental concentrations as parameters of resource allocation. For the first time, we apply the biogeochemical niche (BN) concept to a mutualism and construct the BN of syconial occupants using the elementomes and stoichiometric ratios of plant, seed and pollinator tissue. We predicted that BNs of seeds and galls containing wasps should differ due to differences in tissue type, facilitating their co-development. We also measure trophic stoichiometric ratios (TSRs) for various elements to determine resource mismatch between consumers and resources. We found that the syconium wall, which insulates and protects developing seeds and wasps, constituted 58% of syconial biomass. Individual pollinators and their galls were significantly heavier than seeds indicating that their development is resource-intensive. As predicted, seeds and adult female pollinators had significantly different BNs, highlighting differences in nutritional needs of these mutualistic occupants within a shared nutrient-providing resource. Pollinators had significantly lower C:N and C:P ratios than the syconial wall indicating limitation of N and P within host resources. The BN of pollinator wasps was distinguished by significantly higher concentrations of nitrogen, phosphorus, zinc and sulphur compared to the syconium wall or seeds. TSRs of >4 for nitrogen and sulphur highlight the heightened resource mismatch that pollinators likely face for these elements during their development. We found no overlap in the BNs of male and female pollinator wasps, likely due to their starkly different anatomical and functional traits. Overall, our study demonstrates how BNs and TSRs can reveal trading of resources within mutualisms highlighting non-overlapping requirements for elements and the potential limitations they can pose for resource providers and consumers. These parameters can serve as common currencies for comparisons across mutualistic interactions.
Host manipulations within mutualisms: Role of plant hormones in selective resource allocation
(Springer Nature Publishing AG, 2025) Kulkarni, Manasa; Vadassery, Jyothilakshmi; Borges, Renee M.
In some mutualisms involving host plants, photoassimilates are provided as rewards to symbionts. Endophagous organisms often manipulate host plants to increase access to photoassimilates. Host manipulations by endophagous organisms that are also mutualists are poorly understood. We show host plant manipulations by symbionts and the role of phytohormones, i.e. the auxin indole-3-acetic acid (IAA), and the cytokinin trans-zeatin (tZ), in the brood-site pollination mutualism between fig trees and pollinator fig wasps. In this interaction, pollinator wasps pollinate Ficus flowers within an enclosed inflorescence called a syconium, in exchange for flowers that develop into galls nourishing pollinator offspring. To examine host manipulation by pollinator galls by affecting host fitness through seed reduction, we compared growth hormones released by syconial occupants within three experimentally produced treatment groups of syconia: S (containing only seeds), G (containing only pollinator galls) and SG (containing seeds and pollinator galls). We harvested syconia from each treatment in early and mid-phases of syconial maturation when maximal growth occurs and measured hormone levels. Hormones were reduced by mid-phase in general; however, their levels were mostly sustained in G syconia in the mid-phase, suggesting that galls manipulate the host to continuously access resources. We found no difference in IAA and tZ levels of S and G syconia. IAA concentrations were higher in SG syconia. From the perspective of the maintenance of mutualism, syconium volume and hormone concentrations were highest when both seeds and galls were present (SG treatment), indicating that both partners control allocation of resources to syconia.