Plant‐sex‐biased tritrophic interactions on dioecious willow

Abstract

Abstract. Plant sex effects on herbivores are well studied, but little is known about these effects on predators and predator-herbivore dynamics. Here we take a holistic approach to study, simultaneously, plant sex effects on herbivore and predator preference and performance, as well as population densities and predation pressure in the field. For dioecious Salix cinerea (grey willow) we found that male plants represented higher host plant quality than females for an omnivorous predator (Anthocoris nemorum, common flower bug), while host plant quality for its herbivorous prey (Phratora vulgatissima, blue willow beetle) was not sex-biased. The herbivore strongly preferred the host plant sex (female) that was suboptimal for the predator, which in turn followed its prey to female plants, leading to plant-sex-biased predation. These results provide new insight into the far-reaching effects of plant sex on insect communities, and open up novel opportunities for improving biocontrol of the herbivore in Salix short rotation coppice.

Relative effects of genetic variation sensu lato and sexual dimorphism on plant traits and associated arthropod communities

“…Similarly, Boecklen et al (1990) found that male willows supported higher densities of five species of tenthredinid sawflies than do female willows. However, plant sex might also determine the structure of associated multitrophic communities (Petry et al 2013;Kabir et al 2014;Abdala-Roberts et al 2016). For example, Petry et al (2013) found higher predator to herbivore ratios on Valeriana edulis females relative to males.…”

Plant sex effects on insect herbivores and biological control in a Short Rotation Coppice willow

“…Notably, it does so even though predation rates on female plants from the common flowerbug (Anthocoris nemorum L.), an anthocorid that is an omnivorous predator which feeds on P. vulgatissima eggs and Salix spp. nectar, are higher (Kabir et al, 2014). Such effects on insect preference and performance indicate that manipulating plant sex may be a powerful component of the IPM toolbox for Salix.…”

“…Plant sex is often an important trait structuring herbivory (Cornelissen and Stiling, 2005) in wild plants. Predation can also be affected by plant sex (Kabir et al, 2014;Mooney et al, 2012), and studies on its potential utility in IPM programs including dioecious crops are therefore merited. Previous studies have shown that wild male and female plants can differ with respect to both resistance and rewarding traits (Bañuelos et al, 2004;Boecklen et al, 1990;Bullock, 1984;Pollard and Briggs, 1984).…”

“…and poplar (Populus spp.) in Short Rotation Coppice (Peacock et al, 2001), prefers female plants of the wild crop relative Salix cinerea in natural populations (Kabir et al, 2014). Notably, it does so even though predation rates on female plants from the common flowerbug (Anthocoris nemorum L.), an anthocorid that is an omnivorous predator which feeds on P. vulgatissima eggs and Salix spp.…”

“…In addition, we performed a series of greenhouse and laboratory experiments in which we estimated plant sex effects on insect preference, development, survival, consumption, oviposition and predation. Based on previous findings with P. vulgatissima and A. nemorum (Kabir et al, 2014), we hypothesized that (i) abundances of the herbivore and omnivore should be higher on female S. viminalis, and that (ii) monosexual female fields should host greater abundances of both insects than male fields, with mixed-sex fields having intermediate abundances. We further hypothesized that (iii) insect performances would be better on female plants.…”