Habitat complexity advances developmental timing and modulates spatial aggregation across life stages in the yellow mealworm Tenebrio molitor L

Habitat structure can influence population dynamics by altering movement and encounter rates, yet classical models often assume that habitats are spatially homogeneous. To isolate the demographic effects of structural habitat complexity, we compared the population dynamics and spatial distribution of the yellow mealworm ( Tenebrio molitor ) in two standardized environments: an undivided Open arena and a compartmentalized Maze arena. Structural complexity advanced developmental timing without affecting the upper asymptotic population size. Pupal populations in the Maze reached half-peak abundance approximately five days earlier than those in the Open habitat (129 vs. 134 days), while the estimated timing of adult emergence, derived from the time adults reached half-peak abundance ( a ), was advanced by 4.36 days (138.56 vs. 142.92 days). Still, the intrinsic adult population growth rate ( r ) and upper asymptotic population size/carrying capacity (K) did not differ between the two environments (Maze: r = 0.28, K = 56.47; Open: r = 0.24, K = 63.48). Spatial analyses revealed stage-specific patterns of aggregation. Pupae in the Maze habitat aggregated within structurally complex areas. In contrast, adults in the Open habitat exhibited strong late-stage aggregation in a single area; however, in the Maze, they remained more evenly distributed, consistent with movement constraints imposed by physical barriers. Despite differences in developmental timing and spatial distribution, population trajectories ultimately converged, suggesting compensatory population dynamics. Structural complexity, therefore, influenced population growth pathways without altering the population growth rate and upper asymptotic size. These findings highlight a key limitation of classical non-spatial models. Although they may accurately predict final population size, they ignore the spatial processes and movement constraints that determine how populations reach it.