The ecological footprint of plant sex: implications for soil microbial and arthropod communities

Many dioecious plants, consisting of males and females, are dominant foundational species that structure ecosystems and provide essential resources for diverse ecological communities. Soils supply the substrate, nutrients, and habitat necessary to support all terrestrial plant communities, yet male and female plants are believed to engage with the soil environment in different ways. Given their higher reproductive costs, females often exhibit greater nutrient requirements, which may increase their dependence on soil microbial communities and associated soil fauna, with cascading effects on ecosystem processes. While recent studies suggest that female and male plants can differ in soil microbial diversity and community composition, the findings are inconsistent. Furthermore, almost nothing is known about whether these sex-based differences extend to higher trophic levels such as soil arthropods. We investigated how female and male plants of Ilex vomitoria differ in microbial diversity and composition and cascading effects on soil arthropod communities. Microbial operational taxonomic units (OTUs) were identified from next-generation DNA sequencing, and arthropods were extracted and identified from 91 soil samples collected beneath female and male I. vomitoria canopies across three locations in southeastern Texas, USA. We found that male plants of I. vomitoria exhibit higher microbial diversity compared to female plants, with both sexes associating with distinct microbial communities. Conversely, soil arthropod diversity and community composition were affected by location but not plant sex. Our results provide valuable insights into the ecological interactions of dioecious plants, emphasizing the role of plant sex as a key trait that influences soil biodiversity and the associated functioning of ecosystems.