Collembolan communities were sampled at three plots along a gradient of increasing pollution by heavy metals (Zn, Pb and Cd) in a poplar plantation downwind of a zinc smelter (Auby, France). Despite stability of both total abundance and total number of species, pronounced changes were observed in species distribution, gut contents and mode of reproduction. Metal pollution caused environmental changes which affected species assemblages both by changing habitat (shift from woodland to grassland, accumulation of undecayed litter) and food, together with probable toxicity. We observed that hemiedaphic species (species living in litter) were disfavoured compared to species living either at the ground surface or in deep soil, which we interpreted as avoidance of toxic litter. We also demonstrated plasticity of the food diet, together with other, more species-specific adaptive processes. Protaphorura armata increased its moulting rate, thereby detoxifying its gut, as assessed by a higher number of exuviae in its food bolus. Mesaphorura macrochaeta shifted from obligate parthenogenesis to sexual reproduction, thereby increasing fitness of the population.