Câmara Talita, Cavalcante Nathália Thais, Falcão Hiram Marinho, Santana Esther, Dos Santos Silva Teixeira Giselle, Arnan Xavier
Universidade de Pernambuco-Campus Garanhuns, Rua Capitão Pedro Rodrigues, 105-São José, Garanhuns, 55294-902, Brazil.
Programa de Pós-Graduação Em Ciência E Tecnologia Ambiental, Universidade de Pernambuco-Campus Petrolina, BR 203, KM 2-Vila Eduardo, Petrolina, 56328-900, Brazil.
Oecologia. 2024 Dec 10;207(1):8. doi: 10.1007/s00442-024-05646-4.
Mutualisms may be more or less sensitive to environmental conditions depending on the diversity and responses of the species involved. Ants frequently form mutualistic associations with plants bearing extrafloral nectaries (EFNs): the ants protect the plants from herbivores and receive food resources (i.e., nectar) in return. As ectotherms, ants are strongly influenced by temperature, and temperature shifts can affect ant-plant interactions in ways that often depend on species functional traits. In this study, we explored the influence of EFN size and leaf surface temperature on ant-plant interactions in a Caatinga dry forest in Brazil. We observed the ants visiting 14 EFN-bearing plant species at different times of day over 12 sampling months; we also measured leaf surface temperatures during these periods. We next quantified EFN size for 68 individuals from the 14 plant species. The observational data were used to characterize the heat tolerance of the attendant ant species (i.e., based on levels of foraging activity). We then evaluated the mutualism's degree of functional resilience using two indices: functional redundancy (i.e., the number of ant species interacting with a given plant species) and thermal response diversity (i.e., variability in the heat tolerance of the ant species interacting with a given plant species). We found that leaf surface temperature, but not EFN size, had an influence on mutualism functional resilience. As temperatures increased, both functional redundancy and thermal response diversity decreased. This result implies that warmer global temperatures could heighten the vulnerability of facultative ant-plant mutualisms, regardless of plant traits.
根据所涉及物种的多样性和反应，共生关系对环境条件的敏感程度可能会有所不同。蚂蚁经常与带有花外蜜腺（EFN）的植物形成共生关系：蚂蚁保护植物免受食草动物侵害，并获得食物资源（即花蜜）作为回报。作为变温动物，蚂蚁受温度影响很大，温度变化会以通常取决于物种功能特征的方式影响蚂蚁与植物的相互作用。在本研究中，我们探讨了花外蜜腺大小和叶片表面温度对巴西卡廷加干旱森林中蚂蚁与植物相互作用的影响。我们在12个采样月的不同时间观察了蚂蚁拜访14种带有花外蜜腺的植物物种的情况；我们还测量了这些时期的叶片表面温度。接下来，我们对14种植物物种中的68个个体的花外蜜腺大小进行了量化。观测数据用于表征伴随蚂蚁物种的耐热性（即基于觅食活动水平）。然后，我们使用两个指标评估共生关系的功能恢复力程度：功能冗余（即与给定植物物种相互作用的蚂蚁物种数量）和热反应多样性（即与给定植物物种相互作用的蚂蚁物种耐热性的变异性）。我们发现，叶片表面温度而非花外蜜腺大小对共生关系的功能恢复力有影响。随着温度升高，功能冗余和热反应多样性均降低。这一结果意味着，全球变暖可能会增加兼性蚂蚁与植物共生关系的脆弱性，而与植物特征无关。
