Florivory indirectly decreases the plant reproductive output through changes in pollinator attraction

Abstract

Species often interact indirectly with each other via their traits. There is increasing appreciation of trait‐mediated indirect effects linking multiple interactions. Flowers interact with both pollinators and floral herbivores, and the flower‐pollinator interaction may be modified by indirect effects of floral herbivores (i.e., florivores) on flower traits such as flower size attracting pollinators. To explore whether flower size affects the flower‐pollinator interaction, we used Eurya japonica flowers. We examined whether artificial florivory decreased fruit and seed production, and also whether flower size affected florivory and the number of floral visitors. The petal removal treatment (i.e., artificial florivory) showed approximately 50% reduction in both fruit and seed set in natural pollination but not in artificial pollination. Furthermore, flower size increased the number of floral visitors, although it did not affect the frequency of florivory. Our results demonstrate that petal removal indirectly decreased 75% of female reproductive output via decreased flower visits by pollinators and that flower size mediated indirect interactions between florivory and floral visitors.

Community‐wide consequences of sexual dimorphism: evidence from nectar microbes in dioecious plants

“…e) and a decline in microbial dispersal, but nectar concentration might be more likely to underlie the results that support hypothesis 2, as we observed a greater increase in nectar concentration in male flowers (Fig. e), whereas no obvious inherent difference in animal visitation was found between male and female flowers (Tsuji and Ohgushi ).…”

“…1a-d), including flies, midges, and bees. Previously, we reported that some of these insects were sometimes more frequently found around male plants than around female plants, but the difference was small and inconsistent between years (Tsuji and Ohgushi 2018). Floral longevity is similar between plant sexes (mean of 9 and 11 d for female and male flowers, respectively, in E. japonica; see Appendix S1: Table S1).…”

“…), we hypothesized that microbial abundance would be lower in female flowers. Sugar concentration might also affect insect visitation to flowers, but our previous study suggested that neither the frequency nor composition of insect visitors differed greatly between female and male flowers (Tsuji and Ohgushi ). Thus, we expected sexual differences in nectar chemistry, rather than insect visitation, to be more important in determining nectar microbial abundance.…”

“…In E. japonica, flower size is positively correlated with the number of insect visitors for a given amount of sugar in nectar (Tsuji and Ohgushi 2018). Despite this correlation, there is little difference in insect visitors between females and males (Tsuji and Ohgushi 2018), suggesting that female and male flowers may have evolved to attract pollinators using different floral traits, that is, a greater reward (more sugar) and a greater signal (larger size), respectively. Because high sugar concentration can increase the level of chemical stress that limits microbial survival and growth (Pozo et al 2012, Letten et al 2018, we hypothesized that microbial abundance would be lower in female flowers.…”

Sexual and temporal variations in floral scent in the subdioecious shrub Eurya japonica Thunb

“…Flower diameter and length are approximately 2-5 mm and 3-5 mm, respectively. E. japonica is an insect-pollinated plant, its pollinators are mainly dipteran and thysanopteran insects (Kitamoto et al, 1992;Tsuji & Ohgushi, 2018), and its florivores are generally lepidopteran and dipteran larvae and hemipteran insects (Tsuji & Sota, 2013).…”