Elevation-Driven Turnover of Ant Assemblages (Hymenoptera: Formicidae) in a Mediterranean Mountain System: Diversity, Seasonality, and Thermal Drivers in Al-Jabal Al-Akhdar, Libya

Abstract

Elevational gradients act as natural laboratories for isolating the climatic constraints on insect diversity, yet Mediterranean North Africa remains one of the least-documented regions for such analyses despite hosting internationally recognised biodiversity hotspots. We present the first systematic, multi-seasonal survey of epigaeic ant (Hymenoptera: Formicidae) assemblages along a 30–625 m elevational transect in Al-Jabal Al-Akhdar, north-eastern Libya, and use it to test how altitude and local microclimate jointly structure community composition, dominance and phenology in an understudied Mediterranean-type ecosystem. Standardised time-unit hand collection was carried out at three sites spanning the gradient (coastal Ras Al-Helal, ~30 m; intermediate Al-Wasita, ~220 m; highland Sidi Al-Hamri, ~625 m) across four seasons between June 2025 and March 2026. A total of 1,505 individuals representing seven species were recorded. Overall community diversity was moderate-to-high (Shannon–Wiener H′ = 1.88; Simpson's index of diversity, 1–D = 0.84) and increased with elevation (H′ = 1.54 at the coast to 1.92 in the highlands), a pattern that diverges from the monotonic richness declines typical of temperate mountains but parallels several recent Mediterranean and arid-zone elevational studies. Thermophilic, open-habitat taxa (Cataglyphis cf. albicans, Solenopsis fugax) dominated the coastal lowlands, mesic forest specialists (Camponotus barbaricus) prevailed in the highlands, and the granivorous Messor ebeninus displayed marked ecological plasticity across the gradient. Ant abundance was strongly and positively correlated with air temperature (r = 0.52–0.88) and negatively correlated with relative humidity (r = –0.42 to –0.75), corroborating thermal-constraint models of ant foraging activity. These results establish Al-Jabal Al-Akhdar myrmecofauna as a sensitive bioindicator system for Mediterranean climatic gradients and provide a quantitative baseline for detecting future climate-driven range shifts in a chronically under-surveyed part of the Mediterranean Basin.