Relative importance of diurnal and nocturnal pollinators for reproduction in the early spring flowering shrub Stachyurus praecox (Stachyuraceae)

Daichi Funamoto,Shinji Sugiura

doi:10.1111/1442-1984.12299

Abstract

AbstractGeneralized pollination systems may be favored in early spring flowering plants, as during this period pollinator activity is unpredictable. Many previous studies have concentrated on the importance of diurnal visitors in pollination, and consequently, information on the contribution of nocturnal visitors to pollination in early spring is limited. This study was conducted to evaluate the relative importance of diurnal and nocturnal pollinators in the early spring flowering dioecious shrub Stachyurus praecox (Stachyuraceae), in two temperate forests in central Japan. Visitors to the female and male flowers were observed during day and night, and their relative contributions to seed set were compared. The pollinator observations revealed that the diurnal and nocturnal insects visited both male and female flowers, and that the main flower visitors were diurnal small bees and flies as well as nocturnal settling moths. The diurnal and nocturnal flower visitors also acted as pollinators, as the pollen grains of S. praecox were attached to the insects collected from the female flowers. Pollination experiments demonstrated that the contributions of diurnal pollinators to the seed set were higher than those of the nocturnal pollinators. The results of this study indicate that S. praecox has a generalized pollination system, comprising both diurnal insects and nocturnal settling moths. Although the roles of diurnal insects are more important in the pollination of S. praecox, nocturnal settling moths may have a complementary role in early spring.

Highlights

Plants pollinated by multiple groups of animals might have advantages because different groups of pollinators can be complementary to each other (Blüthgen &Klein, 2011; Macgregor, Pocock, Fox, & Evans, 2019).Generalized pollination systems are widespread in angiosperms (Funamoto, 2019; Leal et al, 2020; Waser, Chittka, Price, Williams, & Ollerton, 1996)
This study aims to address the following question. (a) Do both diurnal insects and nocturnal moths visit flowers across years and sites? (b) Are both diurnal and nocturnal flower visitors carrying pollen grains of S. praecox? (c) Do both diurnal and nocturnal flower visitors contribute to the seed production of
The numbers in parentheses indicate the sample size natural pollination experiment produced significantly fewer seeds than the diurnal pollination experiment (t = −2.395, p = .022, adjusted p = .027) and cross-pollination (t = −3.407, p = .002, adjusted p = .003). This investigation showed that S. praecox has a generalized pollination system that includes both diurnal and nocturnal pollinators

Summary

| INTRODUCTION

Plants pollinated by multiple groups of animals might have advantages because different groups of pollinators can be complementary to each other The contribution of nocturnal moths to pollination has been experimentally examined in only two species of early spring flowering plants, D. laureola and S. caprea (Alonso, 2004; Jürgens et al, 2014). The flowers of S. praecox attract diverse insects, including small bees, hoverflies and bee flies during the day (Abe, 2007), whereas settling moths visit the flowers at night (Ikenoue, 1990; Ikenoue & Kanai, 2010). Both diurnal and nocturnal pollinators may be involved in the pollination of flowers.

| MATERIALS AND METHODS

| RESULTS

Findings

| DISCUSSION