Quasi-continuous variation of the first premolars in the Polish population of the badger Meles meles

The presence-absence polymorphism and the size of P1] were studied in the Polish population of the badger Meles meles (Linnaeus, 1758} (n = 79). P1 is more often absent than Pi. The lengths of P\ range from 0.97 mm to 2.63 mm (V = 16.3-22.3). A breach in the continuous variation of the size of the teeth between their absence and the minimum length of the crown that is 0.97 mm suggests that a threshold mechanism, related to size, operates at an early stage of P'i ontogeny. Such a mecha­nism would allow the development of a tooth only if it had reached the threshold size at the critical stage of its ontogeny. The correlation between the presence or absence of P!i and the number of roots of P% confirms the existence of a gradient in shape ancf size within the morphogenetic field of cheek teeth. The frequent occurrence of P i in the Polish population of the badger (73%) corresponds to the clinal variation of the presence-absence polymorphism of the first premolars in Eurasia.