Unraveling the Adaptive Chemical Traits of Rhamnidium elaeocarpum in Response to Fire and Environmental Factors in Pantanal Wetlands

Abstract We conducted a study on the effects of fire on Rhamnidium elaeocarpum , a widely distributed woody species found in the Pantanal wetlands, using LC-MS metabolomics, total phenolic and tannin content analysis, and thermogravimetric behavior. We sampled individuals from four different groups and found that recent fires had no significant impact on the species' phenolic metabolism, except for those specimens whose aerial parts had died during the 2020 megafire, which showed a compound decline due to leaching. The high levels of phenolics in R. elaeocarpum suggest that the species has a biochemical tolerance to the stress caused by seasonal fires. Metabolomic profiling revealed the presence of proanthocyanidin oligomers, which protect against oxidative stress and post-fire environmental disturbances. However, the passage of fire also led to a high incidence of toxic karwinaphthopyranone derivatives, which could be a concern for the species' medicinal use. Finally, the thermogravimetric analysis showed that the species is thermotolerant, with an intrinsic relationship between the secondary compounds and thermotolerance. Our study enhances our understanding of the impact of fire on woody species' metabolism, although distinguishing whether chemical traits are an adaptive feature or a response to surrounding environmental factors is challenging.