Chromosome Number and Mode of Reproduction in theBothriochloininae

Abstract

The genus Bothriochloa is characterized by chromosome numbers ranging almost continuously in multiples of 10 form 2n = 20 to 2n=180. Chromosome numbers of 2 n = 20, 40 and 60 were encountered in Dichanthium. The genus Capillipedium is characterized by 2n=20, 40 and 50 chromosomes, while representatives of the genera Euclasta and Eremopogon, which were studied, are tetraploids (2n = 40). In these genera diploids (2n = 20) reproduce sexually, tetraploids are mostly facultative apomicts, and higher polyploids are essentially obligate apomicts. Exceptions are the American and some Australian polyploid representatives of Bothriochloa (2n = 60, 80, 120, 180) which reproduce sexually. The diploids are all narrow endemics, the facultative apomicts are widely distributed, and the sexually reproducing as well as apomictic polyploids are usually restricted in their distribution range.