XVI International Botanical Congess
The long-distance dispersal hypothesis was tested experimentally in species of bryophytes and ferns by means of spore viability tests. Drought and frost resistance were studied in the laboratory. UV impact was determined at jet stream altitudes (10.000-12.000 m) by flying spores across the Atlantic on the wings of a KLM jumbo jet. The results indicate that widespread species generally have more resistant spores than endemic ones. UV radiation at jet stream altitudes is usually lethal except in a few very widespread or alpine species. It is concluded that effective long-distance transport of spores may very well have occurred via birds or air streams at rather low elevations, below 3000 m, but is unlikely to operate via jet streams.