Arthropod Assemblages in Desert Ecosystems of Alula County, Saudi Arabia

Despite their ecological importance, epigeic arthropod assemblages in hyper-arid systems remain understudied, particularly across the Arabian Peninsula. We provide an initial description of epigeic arthropod assemblages sampled in two protected areas in AlUla County in the Kingdom of Saudi Arabia, comparing arid thorn woodland and wadi habitats. Standardised pitfall trapping was done across eight sites during a single 6-day sampling period in spring 2024. Arthropod assemblages differed between habitat types in abundance, diversity and evenness, while higher-level taxonomic composition was broadly similar. Arid thorn woodlands tended to support greater arthropod abundances, largely driven by ants (order Hymenoptera: family Formicidae), whereas wadis supported more even and morphospecies-diverse assemblages. Springtails (class Collembola: specifically order Entomobryomorpha) accounted for 24% of all individuals sampled and were recorded across both habitat types despite extreme aridity. We also report the first local records, to our knowledge, of the spider family Tetragnathidae in AlUla County, based on three morphospecies. These findings provide an initial empirical reference for a poorly studied hyper-arid region and highlight the need for expanded temporal sampling, broader habitat coverage and improved taxonomic resolution to better characterise arthropod assemblage patterns and their potential relevance for monitoring and management.