Pollinator preference and pollen viability mediated by flower color synergistically determine seed set in an Alpine annual herb.

Junpeng Mu,Karl J Niklas,Yanling Luo,Yulian Yang,Ruijun Su

doi:10.1002/ece3.2899

Junpeng Mu, Karl J Niklas + Show 3 more

Open Access

https://doi.org/10.1002/ece3.2899

Copy DOI

Abstract

Gentiana leucomelaena manifests dramatic flower color polymorphism, with both blue‐ and white‐flowered individuals (pollinated by flies and bees) both within a population and on an individual plant. Previous studies of this species have shown that pollinator preference and flower temperature change as a function of flower color throughout the flowering season. However, few if any studies have explored the effects of flower color on both pollen viability (mediated by anther temperature) and pollinator preference on reproductive success (seed set) in a population or on individual plants over the course of the entire flowering season. Based on prior observations, we hypothesized that flower color affects both pollen viability (as a function of anther temperature) and pollen deposition (as a function of pollinator preference) to synergistically determine reproductive success during the peak of the flowering season. This hypothesis was tested by field observations and hand pollination experiments in a Tibetan alpine meadow. Generalized linear model and path analyses showed that pollen viability was determined by flower color, flowering season, and anther temperature. Anther temperature correlated positively with pollen viability during the peak of the early flowering season, but negatively affected pollen viability during the peak of the mid‐ to late flowering season. Pollen deposition was determined by flower color, flowering season (early, or mid‐ to late season), and pollen viability. Pollen viability and pollen deposition were affected by flower color that in turn affected seed set across the peak of the flowering season (i.e., when the greatest number of flowers were being pollinated). Hand pollination experiments showed that pollen viability and pollen deposition directly influenced seed set. These data collectively indicate that the preference of pollinators for flower color and pollen viability changed during the flowering season in a manner that optimizes successful reproduction in G. leucomelaena. This study is one of a few that have simultaneously considered the effects of both pollen viability and pollen deposition on reproductive success in the same population and on individual plants.

Highlights

Flower color polymorphism has been long of interest to ecologists and evolutionists (Darwin, 1859; Galen, 1999; Stebbins, 1974)
Recent research has shown that flower color polymorphism within a population or on individual plants can be an adaptation to stressful habitats (Arista, Talavera, Berjano, & Ortiz, 2013; Mu, Li, Niklas, & Sun, 2011; Mu, Li, & Sun, 2010; Rausher, 2008; Schemske & Bierzychudek, 2001)
To our knowledge, most studies have focused on how either pollinator preference or stressful habitats drive the flower color polymorphisms, either in the same population or on an individual plant, and few if any studies have simultaneously considered the relationships among flower color polymorphism, pollinator preference, floral temperature, and pollen viability at both the level of a population and the level of individual plants

Summary

| INTRODUCTION

Flower color polymorphism has been long of interest to ecologists and evolutionists (Darwin, 1859; Galen, 1999; Stebbins, 1974). Gentiana leucomelaena provides a model system with which to explore this possibility because flower color polymorphism, pollinator preference and availability, and intrafloral temperature and pollen viability are known to change over the course of the flowering season (Mu et al, 2010, 2011) This species is an alpine herb that blossoms during the early spring, experiences fluctuating temperatures during the course of the flowering season (Mu, Peng, Niklas, & Sun, 2014; Mu et al, 2010), and produces blue and white flowers within populations and on individual plants (Figure 1). For all of the aforementioned reasons, the reproductive biology of G. leucomelaena was used to test the hypothesis that flower color polymorphism affects both pollen viability (through anther temperature) and FIGURE 1 Blue (top) and white (down) flowers of Gentiana leucomelaena in an Alpine meadow of Tibet

| MATERIALS AND METHODS

Findings

| DISCUSSION

| CONCLUSIONS