Bee community and trait‐based responses to fire in a Mediterranean landscape

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Abstract Fire is a major global disturbance affecting the evolution of organisms and shaping plant and animal diversity, especially in fire‐prone regions like the Mediterranean. Yet its impacts on insect‐pollinator communities remain poorly understood. We conducted a 3‐year study on a Greek island, examining spatial and temporal impacts of fire on bee communities and species' functional traits. We compared bee diversity and population sizes in burnt and unburnt sites, by including in our analysis fire severity metrics using dNBR (differenced Normalized Burn Ratio) derived from satellite imaging. We show that fire initially led to increased bee abundance despite having a strong negative impact on floral resources. Burnt and unburnt communities differed significantly in species composition revealing that specific bee taxa drove post‐fire recovery. In post‐fire year 1, the population spike in burnt sites was driven by an increased abundance of below‐ground nesters, excavators and trophic generalists (polylectic); in contrast, the populations of trophic specialists (oligolectic) were negatively affected. By year 3, most differences between burnt and unburnt sites had been alleviated. Multivariate models incorporating fire severity, plant diversity and floral resources revealed that the heterogeneity of fire severity, even within small spatial scales, drove most of the variation in bee populations, followed by flower numbers. Our findings highlight the role of fire as an environmental filter, selecting species with specific traits and shaping distinct post‐fire communities. Notably, within 3 years, burnt bee communities started converging with the unburnt sites, suggesting a relatively rapid recovery of functional composition.

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