Canopy openness increases the diversity of solitary wasps in a subtropical evergreen forest

Forest canopy cover is one of the determinants of understory microhabitats and subsequently has fundamental impacts on the diversity and occurrence of plants and animals. As a group of pest controllers that are highly sensitive to microclimate changes, solitary wasps are likely to be strongly influenced by such canopy‐induced microhabitat variations. However, the distribution patterns of solitary wasp species between open and closed‐canopy habitats in subtropical evergreen forests remain poorly understood, especially regarding the underlying ecological mechanisms and phylogenetic background.

To clarify this issue, we used standardized trap nests in a subtropical evergreen forest in southern China to investigate the changes in taxonomic diversity, species composition and phylogenetic diversity of solitary wasps under two contrasting canopy habitats (i.e., open canopy vs. closed canopy).

We found that wasps of Pompilidae, Vespidae and Sphecidae showed a preference for open‐canopy habitats. Anterhynchium flavomarginatum and Auplopus sp.1 used more nest tubes and constructed more brood cells in open‐canopy habitats than in closed‐canopy habitats, whereas Chalybion hainanense showed higher nest‐box‐level nesting occurrence under open than closed canopies. The number of nesting tubes and brood cells, species richness ( q  = 0), Hill–Shannon diversity ( q  = 1), Hill–Simpson diversity ( q  = 2) and Faith's phylogenetic diversity of solitary wasps were higher in open‐canopy areas than in closed‐canopy areas. The differences in species composition and phylogenetic composition between the two contrasting canopy habitats were due to the replacement of species and phylogenetic lineages, with lower phylogenetic diversity under closed‐canopy areas. Community structure of solitary wasp was significantly associated with elevation, slope and Moran's eigenvector maps (MEM1, MEM11, MEM12).

Our results highlight that open‐canopy habitats significantly enhance solitary wasp diversity. Management of canopy openness may be important for conserving animal species with different phylogenetic lineages and enhancing the diversity and stability of the solitary wasp community. Community assembly of solitary wasps in a subtropical evergreen forest is jointly influenced by environmental factors and spatial factors. These findings provide important insights into the processes underlying species coexistence and community assembly in subtropical evergreen forests.