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Abstract Detail

Ecological Section

Kubota, Shosei [1], Ohara, Masashi [1].

The evolution of self-incompatible and self-compatible populations in a hermaphroditic perennial, Trillium camschatcense: Which is the derivative?

The evolution of selfing from outcrossing ancestors is known to have occurred repeatedly in the angiosperms. Theoretical studies have interpreted the transition as irreversible, from outcrossing to selfing, and phylogenetic analyses involving self-compatible (SC) and self-incompatible (SI) species has basically supported this hypothesis. Trillium camschatcense is a hermaphroditic perennial herb distributed in Hokkaido and northern Honshu, Japan, which contains geographically widespread SC populations and restricted SI populations (Ohara et al. 1996). The purpose of this study is to reveal the evolutionary trends of self-compatibility and self-incompatibility in T. camschatcense, and to examine the selective factors which promoted the differentiation of SC and SI populations. Pollination treatments and genetic analyses demonstrated that potential availability of outcross pollen in SC populations was sufficient, equal to that of SI populations. However, despite the high availability of outcross pollen, the plants in SC populations were losing opportunities for outcrossing owing to preceding selfing, which accompanied severe inbreeding depression. Thus, selective force to complete outcrossing system was apparent in SC populations (e.g. self-incompatibility). Then, to determine the evolutionary direction of mating system, we analyzed cpDNA sequence for 29 SC populations and 10 SI populations and constructed molecular phylogeny. The molecular phylogeny indicated that SI populations were monophyletic, deriving from SC populations. Additionally, SI populations of T. camschatcense are distributed at peripheral of the speciesí range. In general, peripheral populations are expected to diverge via isolation, genetic drift, and natural selection. Thus, geographical distribution also indicates that SI populations are derivative. In view of evidence on reproductive fitness, molecular phylogeny, and geographical distribution, we conclude that the self-incompatible populations in T. camschatcense have evolved from self-compatible populations.

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1 - Hokkaido University, Faculty of Environmental Earth Science, Lab of Ecological Genetics, Sapporo, 060-0810, Japan

Japanese Trillium
mating-system evolution

Presentation Type: Poster:Posters for Sections
Session: P
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM
Number: PEC011
Abstract ID:255

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