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Abstract Detail

On models and methods pertaining to plant reproduction

Masaka, Kazuhiko [1], Takada, Takenori [2].

Phase transition model for monoecy-dioecy linkage in higher plants: from the perspective based on n-player game model.

A floral sex ratio allocation model for monoecy–dioecy linkage in higher plants was demonstrated theoretically using an n-player game model for monoecy (Masaka¬†and Takada, 2006). Compared with non-game models, n-player game models assume realistic populations, that is, the populations are composed of the finite individuals with different reproductive resources. The model for monoecy was based on two assumptions: competitive sharing among males and pollination efficiency specific to pollen vectors. The first assumption is based on a trade-off between females and males within the local breeding population. The second assumption is described by a Poisson distribution for the probability of pollen hitting an ovule. Nash solution of the n-player game model predicted that individuals should change their gender expression in the following order: female phase (female flowers only), male phase (male flowers only), and constant male phase (individuals constantly allocate reproductive resources to male flowers, and remaining resources to female flowers), with increasing reproductive resources. This tendency is similar to the real monoecious species. Although dioecy has been considered to be derivative of monoecy, we did not pay attention to the linkage with dioecy at that time. Then we try to demonstrate the monoecy–dioecy linkage using the previous model. In the present talk, we add the third assumption on inbreeding depression, which is set to examine the appearance of dioecy, as the avoidance of inbreeding will be an important selective force in the evolution of dioecy. Furthermore, we explore Nash solution of dioecy intensively to examine the effect of pollination efficiency. The model analysis reveals that the dioecious condition was derived by a smaller population and lower pollination efficiency compared to the monoecious condition. These results appear to correspond well to real situation; i.e., woodiness, perenniality, aquatic plants, oceanic islands, harsh environments, and unreliable pollinators such as generalist insects are all strongly linked with dioecy. Furthermore, the result of the analysis shows strong inbreeding depression facilitates the appearance of the dioecious condition, implying that the evolution of dioecy was derived through avoidance of inbreeding. Dioecy is considered to be strongly linked with monoecy, and the present model may be able to explain the monoecy–dioecy linkage in higher plants. Furthermore, gynodioecious- and trioecious populations appeared at transition zone between monoecious- and dioecious populations when we conducted the numerical analysis for the ideal populations. This result can be also explained by the empirical information about the gynodioecy and trioecy.

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1 - Forestry Research Institute, Hokkaido Research Organization, Koshunai, Bibai, Hokkaido, 079 0198, Japan
2 - Graduate School of Environmental Earth Science, Hokkaido University, Kita-ku, Sapporo, Hokkaido, 060 0810, Japan

competitive sharing among males
pollination efficiency
inbreeding depression
n-player game model.

Presentation Type: Symposium or Colloquium Presentation
Session: SY09
Location: Summit/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 10:45 AM
Number: SY09007
Abstract ID:351
Candidate for Awards:None

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