An Evolutionary Study of the Fern Asplenium Trichomanes

The aggregate species Asplenium trichomanes includes three different cytotypes:- a diploid with n = 36 chromosomes, a tetraploid with n = 72, and a hexaploid with n = 108. Although the diploid and tetraploid cytotypes are widely though discontinuously distributed in both Northern and Southern Hemispheres, the hexaploid is known only from New Zealand. All three plants are distinguishable on morphological characters, and possess distinctive ecological preferences. Cytogenetic analysis of a series of artificial hybrids between different representatives of the cytotypes obtained from various parts of the world has demonstrated the close genetical inter-relationship of the entire species complex, and given information concerning the nature of relationships existing between and within the three cytotypes.