Polyploidy in mosses

Patterns were examined in published karyological data for 1451 moss species (approximately 16% of the total number of species) from all regions of the world. Assuming that x = 7 is the original basic chromosome number in mosses, all gametophytic numbers n > 9 were supposed to mark polyploids. It was found that 84% of the species had undergone polyploidy in their history. It is assumed that most polyploids in mosses are autopolyploids. Among the polyploids, 28% are high polyploids (species with n > 15). In pleurocarpous mosses, 16% are high polyploids, whereas in acrocarpous mosses 27% are high polyploids. There is no difference in frequencies of high polyploids between the two subgroups of acrocarpous mosses: Haplolepideae-acrocarpae (26%) and Diplolepideae-acrocarpae (27%). A clear correlation was found between the frequency of high polyploids (n > 15) and latitude. The frequency of high polyploids increases from the equator towards the North and South Poles. The percentage of high polyploids jumps dramatically from tropical and subtropical zones (similar to 13%) to temperate and cold climatic zones (over 30%).