Unveiling an intricate relationship: Ficus trees, their associated wasps (Hymenoptera, Chalcidoidea) and another story of invasion in the Iberian Peninsula and Europe

The plant genus Ficus (Moraceae) includes keystone tree species in tropical ecosystems, providing essential resources for a wide range of animals. Due to their ornamental value, fig trees have been introduced beyond their native ranges, often accompanied by their natural pollinators, which in some cases has led to ecological invasions. This study documents, for the first time, the presence of several pollinating and non-pollinating fig wasps (Chalcidoidea) on the Iberian Peninsula, focusing on three exotic Ficus species: Ficus microcarpa L. f., 1782, F. rubiginosa Desf. ex Vent., 1805 and F. macrophylla Pers., 1807.

Through syconia sampling and dissection, we identified six fig wasp species: the pollinators Eupristina aff. verticillata (Waterston, 1921) and Pleistodontes imperialis Saunders, 1882, the gall-formers Eufroggattisca okinavensis Ishii, 1934, Josephiella microcarpae Beardsley & Rasplus, 2001, Walkerella microcarpae Bouček, 1993, and the parasitoid Philotrypesis okinavensis Ishii, 1934. Additionally, we documented several cases of non-native Ficus species reproducing spontaneously in urban areas, suggesting a significant ecological establishment and invasive spread through sexual reproduction.

This spread poses potential risks to urban infrastructure, as the robust root systems of fig trees can damage buildings, pavements, urban trees, and heritage sites. Finally, we observed urban native and non-native bird species consuming mature fig syconia, which likely assist in the dispersal of these plants. Our findings underscore the need for further studies on the ecological impact of introduced Ficus species in non-native regions, their long-term economic consequences for urban heritage, and the continued monitoring of pollinator fig wasp populations.