Phytoseiid Mites: Trees, Ecology and Conservation

The highly variable ’leafscapes’ of plants across the world represent billions of square metres of mite habitat. The phytoseiid mites (Acari: Phytoseiidae), an extremely species-rich group of mostly generalist predators, are providers of ecosystem services for humanity worth many hundreds of millions of dollars annually by helping suppress phytophagous mites and insects in forests, agro-ecosystems, shade-houses and home gardens. In this study, the phytoseiid mite assemblages on the leaves of four species of common tree species, namely oak (Quercus cerris var. cerris), poplar (Populus deltoides, P. nigra) and walnut (Juglans regia), were compared. The three data sets used were generated in three independent seasonal studies in Samsun Province, Türkiye, between 2018 and 2022. In total, mite species in 18 families, including 15 families on walnut, were recorded. Nineteen phytoseiid species in 13 genera, Amblydromalus, Amblyseius, Euseius, Kampimodromus, Neoseiulella, Neoseiulus, Paraseiulus, Phytoseius, Transeius, Typhlodromina, Typhlodromips, Typhlodromus and Typhloseiulus, were collected. Only Eusieus amissibilis was collected from all three tree genera, whereas 14 species were collected from only one tree genus. Shannon diversity and Jaccard similarity indexes were calculated for mite families and phytoseiid genera and species. Potential reasons for the observed differences in the phytoseiid assemblages on the different host trees are explored in depth. In the ‘big picture’, global biodiversity, likely including many undescribed phytoseiid species, is threatened by widespread habitat degradation and destruction, especially in the tropics, and accelerating climate change, and rapidly stopping them is imperative.