Evaluation of pollinator effectiveness based on pollen deposition and seed production in a gynodieocious alpine plant, Cyananthus delavayi.

Lin‐Lin Wang,Zhi‐Qiang Zhang,Yong‐Ping Yang,Yuan‐Wen Duan,Hao Wang,Guo‐Xing Cao

doi:10.1002/ece3.3391

Abstract

Examining variations in pollinator effectiveness can enhance our understanding of how pollinators and plants interact. Pollen deposition and seed production after a single visit by a pollinator are often used to estimate pollinator effectiveness. However, seed production is not always directly related to pollen deposition because not all pollen grains that are deposited on a stigma are compatible or conspecific. In the field, we tested pollinator effectiveness based on pollen deposition and the resulting seed production after single visits by different pollinator groups in a gynodieocious alpine plant Cyananthus delavayi (Campanulaceae). Our results showed that mean pollen deposition was generally inconsistent with mean seed production when comparisons were performed among different pollinator groups and sexes. In general, the correlations were not significant between pollen deposition and seed production in both perfect and female flowers after single visits by halictid bees, bumble bees, and hoverflies. We suggest seed set of virgin flowers after single visits is a more reliable indicator of pollinator effectiveness than pollen deposition and would be a better indicator of pollinator effectiveness for future studies.

Highlights

| MATERIALS AND METHODSCyananthus delavayi Franch. (Campanulaceae) is a prostrate herbaceous perennial endemic to the alpine area of southwest China (Hong & Ma, 1991)
In flowers visited by hoverflies and halictid bees, there was no significant correlation between the number of pollen grains per stigma and seed number per fruit in hermaphrodite and female individuals (Figure 2)
We found no significant correlations between pollen deposition on individual stigmas and seed set after single visits for the different pollinator groups for C. delavayi

Summary

| MATERIALS AND METHODS

Cyananthus delavayi Franch. (Campanulaceae) is a prostrate herbaceous perennial endemic to the alpine area of southwest China (Hong & Ma, 1991). Halictid bees, and hoverflies as the different pollinator groups to compare the number of pollen grains on stigma and seed production. The model included pollinator group (bumblebee, halictid bee, and hoverfly), sex (female and hermaphrodite), and their interaction as fixed effects. The seed production of flowers after single visits was affected significantly by pollinator group, but not by plant sex and their interaction (Table 2). In flowers visited by hoverflies and halictid bees, there was no significant correlation between the number of pollen grains per stigma and seed number per fruit in hermaphrodite and female individuals (Figure 2). In flowers visited by bumblebees, there was no significant correlation between the number of pollen grains per stigma and seed number per fruit of perfect and female flowers (Figure 2c). The sample sizes in the three pollinator groups for hermaphrodite plants are 23, 20, and 25, respectively, and the sample sizes for female plants are 32, 19, and 28, respectively making the results acceptable

Findings

| DISCUSSION

| CONCLUSIONS