Variation in floral sex allocation, female success, and seed predation within racemiform synflorescence in the gynomonoecious Ligularia virgaurea (Asteraceae)

Abstract

Studies of diclinous species have showed that floral sex allocation and female reproductive success were quite variable within inflorescences. However, little attention has been paid to gynomonoecious species, in which individuals produce both female and bisexual flowers. The purpose of this study was to investigate the variations in reproductive patterns at different capitulum positions within racemiform synflorescence in Ligularia virgaurea, and to determine selective mechanisms of variations in reproductive patterns. We conducted observational and experimental studies in natural populations of the gynomonoecious composite L. virgaurea. Floral sex allocation, seed production and pre-dispersal seed predation were quantified in the field. The results showed several patterns of variation from top to bottom capitula, including an increase in bisexual flowers and flower number per capitulum, but a decrease in seed set and size. Removing earlier capitula during bud stage did not change floral sex allocation in later capitula. And no effect was found on seed set under supplemental pollination. Thus, although it has been reported many times in previous studies, the variation of floral sex allocation in L. virgaurea may not result from architectural effect or mating environment, and the variation of seed production could not be fully explained by pollination success. Additionally, our results showed that L. virgaurea was susceptible to high levels of bisexual biased predation, which was greater for top capitula. We therefore suggest that these variations may help to enhance reproductive success of L. virgaurea in the face of bisexual-biased seed predation.

Towards a unified terminology for angiosperm reproductive systems

“…It is argued that gynomonoecy tends to increase the female reproductive success and chances of originating descendants when compared to cosexuality (Yang & Shuangquan 2006). However, other hypotheses have been postulated to explain the occurrence of gynomonoecy, such as the increase of cross-pollination, reduction in sexual interference, increase in pollinator attraction, defense against herbivores and flexible resource allocation (Yang & Shuangquan 2006;Bertin et al 2010;Zhang et al 2012).…”

Sequential decline in fruit resource allocation within inflorescences of Sagittaria trifolia: a test of non‐uniform pollination hypothesis

“…; Buide , ; Guitián ; Zhang et al . ). However, in plants with several hundred ovules per flower, such as S. trifolia , our study may serve as a useful trial in employing a contiguous percentage of decrease to evaluate the degree of linear changes in ovules and seeds.…”

“…Compared with the 3 weeks that fruits need to ripen, the 1-day difference in flowering time should be negligible. Second, is the effect of antagonists on resource allocation patterns, especially herbivores and fruit/seed predators (Zhang et al 2012). Although it is true that plants usually face distinctive predation pressures on flowers and fruits across seasons, which in turn has shaped within-inflorescence resource strategies (Kliber & Eckert 2004), the fruit of S. trifolia is a lightweight achene without any accessory tissue and seems not to have specialist predators (C. Dai, pers.…”

“…Arista et al 1999;Cao et al 2015). Seed set (seed : ovule ratio) seems a more appropriate parameter and has been commonly used to look for additional decreases in seed production (Medrano et al 2000;Kudo et al 2001;Buide 2004Buide , 2008Guitián 2006;Zhang et al 2012). However, in plants with several hundred ovules per flower, such as S. trifolia, our study may serve as a useful trial in employing a contiguous percentage of decrease to evaluate the degree of linear changes in ovules and seeds.…”

Survival and reproduction of plant species in the Qinghai–Tibet Plateau

“…rivularis in eastern parts of the QTP (Zhao et al, ; Guo et al, ). However, like resource allocation patterns, sexual allocation patterns may be affected by both biotic and abiotic factors (Kliber & Eckert, ; Buide, ; Zhao et al, ; Brookes et al, ; Guo et al, ; Liu & Huang, ; Zhang et al, ). For example, Zhang et al () showed that rewarding type (nectarless, nectar and pollen rewarding) can affect sexual allocation in Pedicularis species in the NE QTP.…”