On the meiosis in Paeonia ludlowii (Stern & Taylor) D. Y. Hong, an endangered species of SE Tibet, PR China

The behavior of chromosomes during meiosis in pollen mother cells (PMCs) of Paeonia ludlowii, endemic to SE Tibet, PR China, was investigated in two natural populations represented by 32 individuals. The meiotic abnormalities, including bridges, fragments and univalents, occurred so frequently that they could be found in all individuals. At metaphase I, the mean chromosome configuration of each cell was 2n=10=0.34 I+4.83 II. Most of the chromosomes were ring bivalents, but some were rod bivalents or univalents. Pairing index ranged from 70% to 81.31%. Chromosome bridges, fragments, unequal separation and lagging chromosomes were observed both at anaphase I and at telophase I. All individuals produced bridges/fragments (9.81% of PMCs on average) at anaphase I. This shows that they were all heterozygotes of paracentric inversion. However, there were some variations among the individuals in frequency of bridge occurrence and in size of fragments, which indicates that many different inversions exist in this species. Further evidence is needed to answer why the structural heterozygosity exists so widely in the species, and whether there is a relationship between the heterozygosity and ecological adaptation.