Comparative Floral Characters, Pollinator Limitation, and Pollination Success in Different Habitats of Caragana microphylla Lam

Min Chen,Xiao-An Zuo,Xue-Yong Zhao

doi:10.3389/fevo.2020.00170

Abstract

Caragana microphylla Lam plays an important role in desert-grassland revegetation. Plant reproduction in arid regions may be restricted due to the low abundance or visiting frequency of pollinators. We tested the visited flowers, the pollinated flowers and seed production to estimate how pollinator limitation affects the seed numbers of visited and pollinated flowers. We investigated the floral characters, pollinator activities and breeding systems of C. microphylla. Our results showed that pollinator limitation was the dominant limiting factor in seed production. In addition, floral characters were moderately positively correlated, and more open flowers with large corollas and long spurs were observed in the natural plots than in grazed plots. Apis mellifera was the most important pollinator. Our findings further indicate that the number of opening flowers and rate of pollinator visitation were positively correlated. In C. microphylla, insect pollination was dominant in outcrossing, and self-pollination played a supporting role in ensuring successful pollination. This study provides a better understanding of how grazing habitat affects floral characters, pollinator limitation, and pollination success of C. microphylla.

Highlights

In flowering plants, pollination success can be affected by the floral characters, pollinators, and breeding systems (Ashman and Morgan, 2004; Ashman et al, 2004)
The aims of the present study were to (1) detect the possible differences in floral characters and pollinator activity between natural and grazing habitats; (2) determine how pollinator limitation affects pollination success based on the proportion of visited flowers, pollinated flowers, and seed production; and (3) evaluate the correlation between pollinator visitation frequency and open flower number in both habitats
Our findings demonstrated that the plants in the natural plots possess a higher vegetation density (VD), vegetation height (VH), and aboveground plant biomass (AGB) than those in the grazing plots

Summary

Introduction

Pollination success can be affected by the floral characters, pollinators, and breeding systems (Ashman and Morgan, 2004; Ashman et al, 2004). Reports have indicated that measures of pollination success are related to floral traits in flowering plants. Insect pollination success is positively related to the plant height, number of flowers, and spur length in Disa draconis (Johnson and Steiner, 1997; Johnson and Nilsson, 1999; Sun et al, 2009). The number of open flowers could influence attractiveness to pollinators, and the importance of the plant stature for pollination success could depend on the vegetation height (Grindeland et al, 2005; Toräng et al, 2006). Over the past two decades, many plant species relying on less effective pollinators (transfer less pollen) have been shown to present significant decreases in the seed number per flower (Burd, 1994; Michael et al, 2003)

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