Species of Melocactus have massively different spatial distribution patterns. Some species have restricted distribution, while others have wide distribution in semiarid ecosystems. This study confirms whether there is a relation between seed germinative responses under abiotic stresses and species distribution capacity. We evaluated the germinative behaviour of seeds of Melocactus zehntneri and Melocactus sergipensis submitted to water deficit and saline stress. These species have the largest and the smallest geographical distribution in the Caatinga, respectively. To simulate water deficit and saline stress, we used polyethylene glycol and sodium chloride solutions, respectively, with osmotic potentials of 0.0,-0.1,-0.3,-0.6, and-0.9 MPa. In addition, we also determined the osmotic limits of species germination potential through germination modeling. Unexpectedly, M. sergipensis seeds were more tolerant of water deficit and saline stress. This situation refutes the hypothesis that species of wide distribution would be more tolerant to environmental stresses. In addition, seeds of the two cacti species were more tolerant of water deficit than saline stress, indicating that excess salt can be toxic to the embryo and prevent water from entering seeds. The greater tolerance to environmental stresses of M. sergipensis is related to the characteristics of its place of occurrence, where microclimate conditions can be more limiting.