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<p>In severe and variable conditions, specialized resource selection strategies should be less frequent because extinction risks increase for species that depend on a single and unstable resource. <em>Psithyrus </em>(<em>Bombus </em>subgenus <em>Psithyrus</em>) are bumblebee parasites that usurp <em>Bombus </em>nests and display inter‐specific variation in the number of hosts they parasitize. Using a phylogenetic comparative framework, we show that <em>Psithyrus </em>species at higher elevations display a higher number of hosts species compared with species restricted to lower elevations. Species inhabiting high elevations also cover a larger temperature range, suggesting that species able to occur in colder conditions may benefit from recruitment from populations occurring in warmer conditions. Our results provide evidence for an ‘altitudinal niche breadth hypothesis’ in parasitic species, showing a decrease in the parasites’ specialization along the elevational gradient, and also suggesting that Rapoport’s rule might apply to <em>Psithyrus</em>.</p><p> </p>