Abstract
A screening of ploidy level in 2146 individuals from 52 populations of the loach Misgurnus anguillicaudatus in China was
performed. Ploidy level variation and its geographical distribution in this study was combined with previously reported data
from another 28 populations. Two major (2n = 50, 4n = 100) and three minor (3n = 75, 5n = 125, 6n = 150) ploidy levels
were found. Diploids were the dominant ploidy level showing broad ecological amplitude. Tetraploid populations were
dominantly, especially concentrated in the central Yangtze River basin. Diploid and tetraploid individuals were observed to
coexist in seven of the 80 examined populations. In four of those seven populations, no triploids were detected, indicating
reproductive isolation between the two sympatric ploidy levels. In the Liangzi Lake area, the sympatric occurrence of
diploids, triploids, tetraploids, and pentaploids was observed, although the triploids and pentaploids were rare (0.1%). In the
Diaochahu area, Yangtze River basin, two male hexaploids were found. No clearly defined geographical ranges or boundaries
could be identified between the diploid and polyploid M. anguillicaudatus.
