Severe fires alter the outcome of the mutualism between ants and a Neotropical savanna tree

Abstract

Physical disturbances, such as fire, may affect the relationship between ants and plants. We evaluated the extent to which severe fires alter the protective effect of ants against the herbivores of an extrafloral-nectary bearing tree. We performed an ant removal experiment and sampled the ant fauna from the same trees over 4 years: the pre-fire year, the fire-year, and again 1 and 2 years later. Ants reduced insect herbivory in the pre-fire year and in the fire-year but failed to provide any plant protection in the two years after fire. The magnitude of the ant effect on herbivory did not differ between the pre-fire year and the fire-year. Fire reduced the abundance of ants with strictly arboreal-nesting habits. However, in the fire year (but not in the subsequent ones), this decline was compensated by an increase in the abundance of arboreal generalists and ground-nesting ants foraging in trees. Our results indicate that severe fires can affect the strength and direction of the ant effects on herbivory by altering the structure of the arboreal ant community and the abundance of insect herbivores. Fire disturbance is thus an important factor of conditionality of ant-plant mutualisms in fire-prone habitats, like the Cerrado savannas.

Trends and gaps in the study of fire effects on plant–animal interactions in Brazilian ecosystems

“…For example, in our review, we identified that most studies dealing with anthropogenic or with an unknown fire origin (i.e., type of fire) usually did not report fire frequency or any other aspect of the fire regime, such as fire severity. In contrast, the majority of publications that reported some aspects of the fire regime studied prescribed fires (see Massad et al, 2015; Paolucci et al, 2016; Vasconcelos et al, 2020 as examples). Therefore, given that the information about the fire regime is of crucial importance to better understand fire effects on global biodiversity (Bowman et al, 2016) and that different fire regimes differently impact organisms, we argue that some fire parameters such as type of fire, frequency, severity, intensity, and flame height must be informed in future studies to allow a deeper evaluation and a wider perspective of the fire effects on plant–animal relationships.…”

Tendências e lacunas no estudo do efeito do fogo nas interações planta‐animal em ecossistemas brasileiros

“…Por exemplo, em nossa revisão, identificamos que a maioria dos estudos que tratavam de fogo antropogênico ou de origem desconhecida (ou seja, tipo de fogo) geralmente não informava a frequência do fogo ou qualquer outro aspecto do regime de fogo, como a severidade do fogo. Por outro lado, a maioria das publicações que relataram alguns aspectos do regime do fogo estudou fogos prescritos (consulte Massad et al, 2015; Paolucci et al, 2016; Vasconcelos et al, 2020 como exemplos). Portanto, considerando que as informações sobre o regime de fogo são de importância crucial para entender melhor os efeitos do fogo na biodiversidade global (Bowman et al, 2016) e que diferentes regimes de fogo afetam os organismos de forma diferente, argumentamos que alguns parâmetros do fogo, como tipo de fogo, frequência, severidade, intensidade e altura da chama, devem ser informados em estudos futuros para permitir uma avaliação mais profunda e uma perspectiva mais ampla dos efeitos do fogo nas relações planta‐animal.…”

The role of leaf cutting and fire on extrafloral nectaries and nectar production in Stryphnodendron adstringens (Fabaceae, Mimosoideae) plants

“…According to Knoechelmann and Morais (2008), under frequent fire, the presence of ants became greater in plants of S. adstringens in comparison with plants that grew in areas without fire; in particular, the abundance of Camponotus became higher after defoliation caused by fire. According to Rosa et al (2021), intense fire strongly changes the composition of ant species that nest exclusively in trees because they can die, thus reducing the efficiency of protection (Vasconcelos et al, 2020). However, for Camponotus ants, which were observed in S. adstringens , a high mortality is not frequent after moderate fires as demonstrated by Knoechelmann & Morais (2008).…”

“…However, Alves‐Silva & Del‐Claro (2014) demonstrated that, in this specific case, the ants failed to protect regrowth leaves from sucking herbivorous insect attacks because these sucking insects also provided those ants with sugary secretions such as the nectar secreted by the EFNs. On the other hand, in Crematogaster brasiliensis , ants reduced herbivory prior to and immediately after the fire, even though they failed in the protection after two years following the fire event (Vasconcelos et al, 2020).…”