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The life-history characteristics and demography of Allium monanthum Maxim. (Alliaceae) are described here. This is a typical spring ephemeral of temperate broad-leaved deciduous forests in the Japanese Islands and adjacent Far East regions. It possesses a very specialized life-history strategy because it is a monocarpic ‘pseudo-annual’. This tiny wild onion species, with one or two (or very rarely, three) small slender aerial leaves measuring only 10 cm long and 4–6 mm wide, has an exceedingly complex sexuality (i.e. male, female, hermaphrodite, andromonoecy and gynomonoecy). Populations including male and hermaphrodite sexualities are exceedingly limited, and thus far have been found only in a few localities in Yamanashi and Niigata Prefectures, Central Honshu. The sexuality and reproductive systems of this species are extremely complex. The exceedingly low efficiency of sexual reproduction is apparently supplemented by vegetative propagation. A. monanthum is karyologically very complex, including a polyploid series of 2x (2n = 16), 3x (2n = 24) and 4x (2n = 32), with the basic karyotype of n (x = 8) = 7 V + 1I. Also, unique translocations, denoted as TrI, TrIIA, TrIIB and TrIII, are found in diploid males. Some other cytotypes, such as 4x/5I, 4x + 1 and 4x − 1, are also found in tetraploid plants. Such cytological peculiarities form the background of the complex sexuality and predominant asexual reproduction of A. monanthum. |
