Sofía Graffigna, Joana P. Haedo, Gabriel Pompozzi, Sofía Copperi, Guadalupe Peralta, Leopoldo Álvarez, Lucía C. Martínez, Luis I. Pérez, Mara A. Maldonado, Mariana L. Allasino, Michel Sciberras, Mary E. R. Diniz, María P. Pascual Tudanca, Rocío A. González‐Vaquero, Diego P. Vázquez, Juan P. Torretta, Hugo J. Marrero
Abstract Urban ecosystems form fragmented landscapes characterized by low biodiversity and high impervious surface cover, which can affect insect demography and ecological interactions. In particular, solitary wasps may be especially sensitive to urbanization, given their role as important regulators of insect populations through predation and parasitism. We investigated how different degrees of urbanization affect the nesting ecology of three cavity‐nesting solitary wasps of the genus Trypoxylon . We hypothesized that increasing impervious surfaces limits resource availability, thereby impairing wasp nest construction and reproduction. From October 2021 to April 2022, we used trap‐nests to monthly record Trypoxylon aureovestitum, T. platense and T. rogenhoferi nesting at 55 sites distributed across nine cities in the central region of Argentina, spanning a range of areas and population sizes. At each site, we defined a circular 500‐m radius buffer area where we estimated the degree of urbanization (proportion of impervious surface) and measured flower abundance and richness. Abundance of built nests decreased significantly with increasing urbanization, whereas brood cell abundance per nest, the survival of immature stages, sex ratio and the number of parasitized brood cells at each site did not change with urbanization. The sex ratio differed between species, with a female bias in T. aureovestitum , a male bias in T. platense and no clear pattern in T. rogenhoferi . Furthermore, nest abundance increased with floral richness, while brood cell abundance per nest and parasitoid abundance decreased. Urbanization influenced the abundance of Trypoxylon wasps. Specifically, a decrease in nest abundance with increasing urbanization may reduce population sizes, potentially increasing species vulnerability to local extinction. Furthermore, our results suggest that certain species may be more flexible than others, and hence more likely to survive and thrive, in these anthropogenic settings. Finally, the influence of floral resources on wasp reproduction highlights the complex effects that local plant communities have on the reproductive success and ecological interactions of these solitary wasps.