INTRODUCTION
When studying interspecific interactions, we often ignore the potential effects of intraspecific variation. But in the context of the interactions between a plant and its associated arthropod community, the individual-plant traits can have a profound impact on the arthropod community because of the multiple ways in which a plant affects its resident arthropods (Mooney et al. 2012, Abdala-Roberts et al. 2016, Nell et al. 2018, Moreira et al. 2019). For example, for herbivore arthropods, a plant not only constitutes a nutrient resource, but it also provides shelter by modifying microenvironmental conditions like temperature and humidity (Obeso 2002). Because a single plant commonly interacts with more than one individual arthropod, it also influences the arthropod community assemblage; thus, determining the arthropod-arthropod interactions that individual arthropod residents experience (Strong et al. 1984, Schoonhoven et al. 2005).
Because sexual dimorphism in plants is expected to provide consistent variation among groups of individuals of the same species (i.e., males vs females), researchers have often studied the effect that this type of intraspecific variation has on arthropods. Differences between male and female plants have been well documented on vegetative (Nell et al. 2018), reproductive (Delph 1999, Eckhart 1999, Barret and Hough 2013), and defensive traits (Agren et al. 1999, Cornelissen and Stiling 2005, Sargent and McKeough 2022). The effects of these differences on arthropod communities have been explored, primarily through the study of plant-herbivore interactions, like foraging preferences and densities (Danell et al. 1985, Agren 1988, Elmqvist and Gardfjell 1988, Boecklen et al.1990, Hjaltén et al. 1993), or herbivory bias. For a long time, studies pointed to a male-biased herbivory preference as the rule (Agren 1988, Agren et al. 1999, Cornelissen and Stiling 2005), but recently Sargent and McKeough (2022) challenged that view through a meta-analysis that revealed no consistent differences on chemical defenses and herbivory between male and female plants. Even if this study suggests that the effect of sexual dimorphism is not consistent across sexes or plant-lineages, most studies still find an effect on herbivores due to sexual dimorphism which may be given by the differences on the resource allocation to reproduction in each sex (Cornelissen and Stiling 2005).
Why the effects of sexual dimorphism are not consistent across plant groups might be due to sexual dimorphism being only one of the axes of plant-phenotypic variation. One of the most drastic and consistent changes that plants, particularly deciduous ones, experience are phenological changes (Bawa and Opler 1975), and these have the potential to interact and conflate the effects of sexual dimorphism on the arthropod communities. Furthermore, most of the work regarding the effect of sexual dimorphism on arthropod-plant interaction has focused on understanding how differences in plant resource allocation affect pairwise interactions (i.e., plant herbivore interactions). But by affecting the herbivore populations, plant-sex might indirectly affect arthropod carnivores through bottom-up forces (Oksanen1988, Chen and Wise 1999, Gruner 2004; Han et al. 2022), so a community approach might help to unravel patterns on the effect of plant sexual dimorphism in arthropods. So far, very few studies have explored the effect of dioecy on a multitrophic approach (Nell et al. 2018, Tsuji and Fukami 2018). Nell et al. (2018) found that, in Baccharis salicifolia(Asteraceae), plant sex influenced plant traits like flower number, relative growth of the plant, predator density, and arthropod community composition. Tsuji and Fukami (2018) evaluated the effects of dioecy in the shrubs Eurya emarginata and E. japonica on the microbiome community associated with plant nectar. They found that the microbes and fungi that colonize nectar were more abundant in male flowers compared to female flowers; also they found that the composition of microbial species was different between sexes.
The objective of this study was to use a community and year-long (phenological) approach to evaluate the effects of plant sex in the shrub Buddleja cordata Kunth (Scrophulariacae), 1) on several plant traits, 2) on the arthropod community associated to this plant species and 3) on the guild of herbivores and carnivores that inhabit these plants.