Temporal turnover and fire severity shape postfire beetle (Coleoptera) diversity at a forest range edge.

In recent decades, wildfires have increased in frequency and severity, reshaping forest structure and biodiversity. Yet it remains unclear whether postfire insect assemblages are driven primarily by fire severity, vegetation structure, or broader temporal community turnover, particularly in fragmented range-edge forests. We investigated flight-active beetle (Coleoptera) assemblages 2 years after a 2022 wildfire in the Lost Pines region of Texas, an isolated loblolly pine (Pinus taeda L.) forest at the species' western range margin. Using historical data from 2011, we evaluated temporal turnover and compared diversity and assemblage composition between contemporary burned and unburned sites. We also quantified fire severity and vegetation structure to analyze their effects on richness and abundance. Contemporary and burned sites supported higher richness and abundance than historical and unburned sites, although evenness declined as opportunistic species became dominant. Beetle assemblage differed significantly between sampling periods and burn status, indicating substantial temporal turnover amplified by wildfire. Fire severity showed strong positive associations with richness and abundance, whereas vegetation structure played a secondary but important role. Richness and abundance increased with woody plant richness, tree diversity, tree size, live tree density, and shrub richness. In contrast, dead tree variables were generally weak or negative predictors, suggesting that the influence of fire-generated deadwood may be transient and strongest shortly after disturbance. Together, these findings indicate that postfire flight-active beetle assemblages in the Lost Pines are shaped by the interaction of long-term temporal turnover and fire-driven successional dynamics, with fire severity acting as the dominant driver of community change.