ISHIDA, KIYOSHI* AND TSUTOM HIURA. 1Forestry and Forest Research Institute, Hokkaido Research Center, Hitsujigaoka 7, Sapporo 062, Japan 2Tomakomai Research Station, Hokkaido University Forests, Tomakomai 053,Japan.. - Pollen fertility and mating system in an androdioecious tree, Fraxinus lanuginosa in Hokkaido, Japan.
Fraxinus lanuginosa (Oleaceae) is a tree species distributed in
Japan and Korea. In Hokkaido, northern Japan, hermaphrodites and males
commonly coexist in its populations. Hermaphrodites and males had
identical flowering phenologies and pollen morphologies. However, the
mean pollen germination rate on an agar culture medium for pollen from
hermaphrodites was 2.8-3.4 times lower than that for pollen from
males. The average seed set of inflorescences cross-pollinated by
pollen from hermaphrodites was similarly 2.7 times lower than that by
pollen from males. These results suggest that F. lanuginosa is
functionally androdioecious. The estimated outcrossing rate based on
3-4 polymorphic loci ranged from 0.76 to 0.99 in four populations.
These findings help to explain the maintenance of androdioecy in F.
lanuginosa.
Key words: androdioecy, Fraxinus lanuginosa, mating system, pollen fertility