When one’s misfortune favors others: the importance of hollows made by a plague on Neltuma trees to stingless bees nesting in Subtropical Dry forests

The ecological interactions of biota with natural ecosystems are still poorly understood. In Subtropical Dry forests, several stingless bees utilize cavities within trees for nesting. Due to their lack of morphological traits for creating these cavities, bees rely on other mechanisms to access and utilize hollow spaces. In the Argentinian Dry Chaco region, we set two main objectives: (1) Determine the richness of cavity-nesting bees and describe the characteristics of trees selected as substrates, and (2) identify the mechanisms employed by stingless bees in selecting trees with hollows. Observational records were used to identify bee-nesting sites, while standard vegetation inventory was conducted to assess preference. Structural equation models were employed to establish the selection mechanisms of tree species for nesting. We found 139 nests belonging to three species: Plebeia catamarcensis (n = 118), Plebeia molesta (n = 14), and Lestrimelitta (L.) chacoana (n = 2). Stingless bees, particularly smaller species like P. catamarcensis, specifically select Neltuma trees for nest installation. This preference is attributed to the presence of galleries and hollows within the heartwood, created by the larvae of Criodion angustatum beetle. Although the larval action may harm the mechanical structure of the trees and hasten their demise, it simultaneously creates suitable hollow spaces for the establishment of bee colonies. Further investigations into these species interactions within the forest are necessary to enhance management practices in this threatened ecosystem, recognizing the important ecological role of Neltuma genus as crucial for ensuring the availability of nesting substrates for these native stingless bees.