The present study reports the chromosome numbers and meiotic behaviour of 13 populations of four species of the genus Fibigia, including the first cytogenetic report of Fibigia clypeata from Iran. Most populations showed the chromosome numbers 2n = 2x = 16. However, the chromosome numbers of four populations of Fibigia suffruticosa were 2n = 2x = 14. It seems that the species with x = 7 is derived through aneuploidy loss. In addition, intraspecific and interspecific variations in the chromosome number and aneuploidy within Fibigia are discussed. The meiotic abnormalities observed in different Fibigia species included various degrees of fragmented chromosomes, sticky chromosomes, laggards, asynchronous nucleus, formation of multipolar cells, bridges and cytomixis. Various meiotic abnormalities caused pollen sterility and pollen-size variation. We are of the opinion that a direct relationship exists between the occurrence of chromosome number change and environmental stress. So, it seems that aneuploids prefer those environments that have less density and competition of species.
