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Abstract
Meiosis of Paeonia decomposita Hand.–Mazz., an endangered species endemic to China, was investigated in two natural populations represented by 13 individuals. The meiotic aberrances occurred so frequently that all individuals were found to have a certain amount of bridges, fragments and univalents. Mean meiotic chromosome configurations of the species were 2n = 10 = 0.20 I + 4.90 II. Pairing index ranged from 72.97% to 81.37%. Chromosome bridges, fragments, lagging chromosomes, and unequal segregation were observed at both anaphase I and telophase I. Interestingly, all the individuals bore bridges/fragments (7.69% of PMCs on an average) at ana-phase I, indicating that they were all heterozygotes of paracentric inversion. However, variations were found among individuals in frequency of bridge occurrence and in size of fragments, which indicated that many different inversions existed in this species. The chromosome structure heterozygotes found so frequently in natural populations should have a selective advantage. However, further evidence is needed to reveal the mechanism of how and why the species could maintain such frequent chromosome structure heterozygosity in wild populations.