Although the post-dispersal functions of diaspore (fruit and its appendages) have been reported, little is known about their protective/defensive functions. In this context, Rheum nanum diaspores with appendages (persistent inner tepals and/or fruit wings) that experienced pre-dispersal herbivory by insects in natural populations of Rheum nanum were investigated, i.e., the percentage of diaspores with appendages damaged by insects; The data of the seed abortion percentage, seed and embryo masses, and germination of seeds from diaspores with different categories of insect herbivory of R. nanum. 

These experimental indices were used to answer the following questions: 

(1) How prevalent is pre-dispersal insect herbivory in natural populations of R. nanum?

(2) Do seeds abort when diaspores receive pre-dispersal insect herbivory? 

(3) What are the impacts of pre-dispersal insect herbivory on seed mass and germination of R. nanum?

Investigate the diaspores with appendages (persistent inner tepals and/or fruit wings) that experienced pre-dispersal herbivory by insects in natural populations of Rheum nanum; measure and compare the seed abortion percentage, seed and embryo masses, and germination of seeds from diaspores with different categories of insect herbivory. 

All data were expressed as the mean ± SE. To meet the requirements of one-way analysis of variance (ANOVA), all data were analyzed for normality and homogeneity of variance before analysis. If data were normal and homogeneous, they were subjected to further analysis. If data exhibited a nonnormal distribution or variances were not homogeneous, treatment differences were assessed by using the more conservative Kruskal‒Wallis nonparametric test.

The Kruskal‒Wallis nonparametric test was used to determine if there were differences in the percentage of diaspores with different categories of insect herbivory in natural populations, seed abortion in diaspores with different categories of insect herbivory and the effect of pre-dispersal insect herbivory on seed development.

A generalized linear model (GLM) with a logit-link function with germination as a binomial response variable (two categories: germinated versus non-germinated) was used to test the significance of the main effects (temperature and light) and their interaction on germination in ‘seed germination of freshly-matured seeds’ experiment in SPSS 26.0 (SPSS Inc., Chicago, IL, U.S.A.). The significance of the effects of temperature, light, and their interaction in the model was tested by Wald χ² values.

The least significant difference (LSD) test was performed for multiple comparisons to determine significant (P < 0.05) differences among categories of insect herbivory, in which the P value was adjusted by Bonferroni correction. All data analyses except those from the ‘seed germination of freshly-matured seeds’ experiment were performed with R 4.2.2 software (R Development Core Team, 2022).