Genetic and reproductive characterization of distylous Primula reinii in the Hakone volcano, Japan: implications for conservation of the rare and endangered plant

Masaya Yamamoto,Honami Sugawara,Kazuhiro Fukushima,Hiroaki Setoguchi,Kaoruko Kurata

doi:10.11609/jott.6532.12.17.17263-17275

Abstract

Genetic and ecological evaluation are crucial in effective management of rare and endangered species, including those exhibiting complex breeding systems such as distyly. We studied a threatened distylous herb Primula reinii in the Hakone volcano, central Japan, to obtain baseline information of reproductive and genetic status towards conservation. In two representative populations inhabiting a central cone and somma of the volcano, population size, floral morph ratio, stigmatic pollen deposition, and fruit-set were measured. Using microsatellite markers, we evaluated genetic diversity, structure and differentiation of populations. Population bottlenecks and historical changes in population size were also estimated from genotype data. We found significant deviation from equal morph ratios in the central cone population, which also exhibited skewed mating success together with a high frequency of pollination within the same morph. These trends were not detected in the somma population. From genetic insights, the central cone population showed slightly lower genetic diversity, whereas no significant deviation from Hardy-Weinberg equilibrium was found in either population. The estimated moderate genetic differentiation and admixed genetic structure suggest recent lineage divergence and/or gene flow between populations. While robust evidence for a recent bottleneck was not obtained in our analyses, a clear signature of historical population contraction was detected in the central cone population. Our findings suggest that the skewed morph ratio strongly influenced the reproduction of small and isolated populations in the short-term, highlighting the vulnerability of distylous plant populations under ongoing anthropogenic pressure.

Highlights

Worldwide, numerous plants are already threatened by human-caused stress and climate changes (Jackson & Kennedy 2009)
Distylous plants usually have a heteromorphic incompatibility system that prevents selfing and intramorph mating (Barrett 2002); only cross-pollination between L- and S-morphs results in seed setting. In theory, such morphologically and physiologically disassortative mating between floral morphs generally leads to an equilibrium with equal morph ratios, as a result of negative frequencydependent selection and simple inheritance of distyly (Heuch 1979; Barret & Shore 2008)
It has been advocated that floral morph bias can be governed by several factors, such as stochastic and deterministic events (Matsumura & Washitani 2000; Kery et al 2003), maternal fitness differences between morphs (Hodgins & Barret 2006), and a combination of weak heteromorphic incompatibility and pollen limitation (Barret 1989; van Rossum et al 2006; Brys et al 2008)

Summary

Introduction

Numerous plants are already threatened by human-caused stress (e.g., habitat destruction) and climate changes (Jackson & Kennedy 2009). Distylous plants usually have a heteromorphic incompatibility system that prevents selfing and intramorph mating (Barrett 2002); only cross-pollination (i.e., legitimate pollination) between L- and S-morphs results in seed setting. In theory, such morphologically and physiologically disassortative mating between floral morphs generally leads to an equilibrium with equal morph ratios, as a result of negative frequencydependent selection and simple inheritance of distyly (Heuch 1979; Barret & Shore 2008). It has been advocated that floral morph bias can be governed by several factors, such as stochastic and deterministic events (Matsumura & Washitani 2000; Kery et al 2003), maternal fitness differences between morphs (Hodgins & Barret 2006), and a combination of weak heteromorphic incompatibility and pollen limitation (Barret 1989; van Rossum et al 2006; Brys et al 2008)

Methods

Results

Conclusion