Stellate hairs on leaves of a deciduous shrub Viburnum erosum var. punctatum (Adoxaceae) effectively protect Brevipalpus obovatus (Acari: Tenuipalpidae) eggs from the predator Phytoseius nipponicus (Acari: Phytoseiidae) by Masaaki Sudo[1] and Masahiro Osakabe

Graduate School of Agriculture, Kyoto University; Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan

SUPPLEMENTAL DATA: Effects of egg age on predation risk

Method

Thirty-five Viburnum erosum var. punctatum (VEP) leaves were set with the adaxial (n = 16) or abaxial (n = 19) side up on water-soaked cotton in Petri dishes in the same manner as described above. On the first day of the experiment, three adult Brevipalpus obovatus females were introduced to each VEP leaf. The position of every egg laid by the females was recorded every day, and the females were removed after 7 days. Then, four adult Phytoseius nipponicus were introduced to each leaf immediately after removing the females. The egg status was checked every day for 3 days after introducing the phytoseiid mites.

A generalized linear mixed model (GLMM), assuming a binomial distribution (logit-link), was used to evaluate the effects of leaf surface and egg age on the predation rate of B. obovatus eggs (the final rate 3 days after predator introduction), in which eggs oviposited on the same leaf were clustered. We constructed the model with the module “glmmML” (in the glmmML package by Broström and Holmberg 2011) of R ver. 2.10.1.

Result

The 3-day predation rate of P. nipponicus on B. obovatus eggs tended to be higher for 1- and 2-day-old eggs than older eggs, although the rate was as high as 0.478 for 6-day-old eggs on the adaxial leaf surfaces (Table S1). Overall, the total 3-day predation rate on the adaxial surface (0.379; n = 195; 95% CI, 0.311–0.452) tended to be higher than that on the abaxial surface (0.312; n = 199; 95% CI, 0.248–0.381). However, the model selection rejected the effects of both leaf surface and egg age on egg predation rate (binomial GLMM, logit-link); The AIC was 486.72, 487.63, and 488.17 in the null model, the model containing “age,” and the model containing “surface,” respectively. Consequently, the effects of egg age and leaf surface on predation risk were not proven.

Reference

Broström G, Holmberg H (2011) glmmML: Generalized linear models with clustering. version 0.81-8

Table S1 Three-day predation rate for 1- to 6-day-old Brevipalpus obovatus eggs on adaxial/abaxial leaf surfaces of VEP.

Egg age / Predation rate
(days) / Adaxial / Abaxial
1 / 0.429 (28) / 0.368 (38)
2 / 0.486 (37) / 0.410 (39)
3 / 0.314 (35) / 0.258 (31)
4 / 0.286 (35) / 0.306 (26)
5 / 0.353 (34) / 0.267 (30)
6 / 0.478 (23) / 0.227 (22)

The numbers in parentheses are the numbers of eggs tested.

[1] E-mail: