Mating Systems of Cyatheaceae Native to Taiwan

Abstract

The mating systems of six species of Cyatheaceae native to Taiwan were characterized by comparing isolated and paired cultures. The genetic loads were: Alsophila fenicis and A. podophylla, 100%; Sphaeropteris lepifera, 85%; A. denticulata, 76%; A. spinulosa, 61%; and A. metteniana, 46%. Genetic load and the frequency of intragametophytic selfing should vary inversely. The diploid species, A. fenicis, A. podophylla, A. spinulosa, and S. lepifera, produced sporophytes primarily by intergametophytic mating, especially intergametophytic crossing. A. metteniana, a tetraploid species, exhibited a high rate of intragametophytic selfing, probably owing to its duplicate genome. However, the duplicate genome of A. denticulata, another tetraploid, did not mitigate depression of intragametophytic selfing. We hypothesize that gene silence is a factor in the high genetic load of A. denticulata, but this has yet to be studied. The similar frequencies of intergametophytic selfing and crossing in both A. denticulata and A. fenicis suggest that the two sources of A. denticulata and the two sources of A. fenicis, which were obtained from small areas, were closely related.