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Arisaema serratum possesses a pitfall-trap flower pollination system. However, little is known about the efficiency and pattern of pollen movement in A. serratum. Thus, the aims of this study are to (1) determine the paternal parents of the seeds and (2) elucidate pollen movement in a natural population. Paternity analysis using microsatellite markers was performed. Seeds were collected from a natural population of A. serratum in 2001 at Horigane, Japan. Small midges became trapped in female spathe tubes during the flowering period. We found that (1) seeds in a fruit were fertilized by multiple sires; (2) seeds sired by a paternal parent were either clumped, exclusively, or randomly distributed on the spadix, depending on the parent; (3) to a great extent, a few males contributed as sires; (4) distance from a female was not a factor in the inequality of reproductive success among males; (5) male reproductive success was not correlated with its size. We conclude that pollen carryover and the trap-flower pollination system are likely to result in multiple paternity and inequality in male success. Key words: Araceae; Arisaema; Japan; male success; microsatellite; paternity analysis; pollen carryover; trap flower.

Fritillaries camtschatcensis, a perennial herb with a complex life history, is discussed relative to estimation and formulation of its effective size of stage-structured populations. Variance effective size is defined in perms of stage-specific parameters and is extended from the equation formulated earlier for a two-stage population.

We compared the life history traits of an amphidiploid species,Drosera tokaiensis(Komiya&C. Shibata) T. Nakamura&Ueda, with those of the parental species, a diploidDrosera rotundifoliaL and a tetraploidDrosera spatulataLabill. to characterize them and clarify the conditions for coexistence. The ranges of the parental species are quite different, but overlap in Japan. The amphidiploid and the parents grow together in some natural habitats. Observations and experiments on reproductive properties were carried out in a glasshouse and a laboratory. Seeds ofD. rotundifoliawere dormant, whereas those ofD. spatulatawere not. InD. tokaiensis, the dormant/non-dormant seed ratio varied from site to site.Drosera rotundifoliahas such life history traits as concentrated flowering and seed dormancy, which are relevant to habitats with short growing seasons and a severe winter.Drosera spatulatahas such traits as a prolonged duration of flowering and non-dormancy, relevant to habitats with long growing seasons and a mild winter.Drosera tokaiensispossesses life history traits of the parental species to various degrees, but exhibits no extreme traits. It is suggested that separation of flowering time and autogamy allow the amphidiploid to coexist with the parental species. [ABSTRACT FROM AUTHOR]

The evolutionary stability of the sex-changing habit of Arisaema serratum was examined. To evaluate reproductive success through male functioin properly, the mathematical formulation of Kakehashi and Harada (1987) was employed. Individuals were classified by both their size and sexual state, and the genetic contribution of individuals was estimated by calculating their reproductive value. It was shown that in the size classes where sex change actually occurs, the reproductive values of males and females are basically the same. This means that the genetic contribution of individuals in these size classes is the same whether they are male or female, and no selection pressure is working to change the male ratio in these classes. Thus, it is concluded that the size at which sex change occurs is evolutionarily stable. The adaptive significance of the size of first reproduction was also discussed. [ABSTRACT FROM AUTHOR]

The sex allocation theory based on size-specific demography is applied to sex change phenomena exhibited by Arisaema serratum, which changes sex expression according to its size. In the evolutionary analysis where adopted strategy correlates with resource level, identifying equal resource level is very important. But directly measured size does not seem to represent the plant's real resource level perfectly. In the analysis presented here, we introduce a new variable that represents the resource level. According to the sex allocation theory, we calculated the transition matrix and other demographic parameters, the stable sex-and-size distribution, and reproductive values. The obtained results were: (1) reproductive values generally increased in accordance with size, but in a different manner for different sexes; (2) in the size class where different sex expressions were adopted, reproductive values for the equal resources were the same; and (3) plant individuals seemed to adopt evolutionarily stable strategies. The adaptive nature of the plant is further discussed. [ABSTRACT FROM AUTHOR]

A projection matrix model was adopted to describe the population dynamics of Arisaema serratum (Thunb.) Schott. This method is most appropriate for describing a complex life history, such as size-specific determination of sex expression in Arisaema. Size classification was determined from both the lilt history stage and the pseudostem diameter at ground level, which was transformed into natural logarithms. The calculated population growth rate based on averaged data from 1981 to 1986 was very close to unity. The survival rate was lowest at the seedling stage and gradually increased for larger size classes. But the survival rate was almost the same for the male stage and female stage irrespective of size classes. Individuals in small size classes made greater contributions to the population growth rate (λ) if they were in the asexual stage than in male or female stages. Those individuals in intermediate size classes had greater effects on λ if they were in the male phase and those in large size classes had greater effects on λ if they were in the female stage. [ABSTRACT FROM AUTHOR]

Arisaema serratum is a perennial herb capable of changing sex expression from year to year. We developed five polymorphic microsatellite markers for A. serratum to estimate male reproductive success. Variability at these loci was examined in two populations, one at Horigane and one at Kanazawa Japan; the number of alleles per locus ranged from five to 35 (the mean 21.4) in Horigane and from three to 36 (22.0) in Kanazawa. This high allelic diversity indicates that our markers are suitable for the study of male reproductive success in A. serratum. [ABSTRACT FROM AUTHOR]