Cuticular hydrocarbons (CHCs), the dominant fraction of the insects’ epicuticle and the primary barrier to desiccation, form the basis for a wide range of chemical signaling systems. In eusocial insects, CHCs are key mediators of nestmate recognition, and colony identity appears to be maintained through a uniform CHC profile. In the unicolonial Argentine ant Linepithema humile, an unparalleled invasive expansion has led to vast supercolonies whose nestmates can still recognize each other across thousands of miles. CHC profiles are expected to display considerable variation as they adapt to fundamentally differing environmental conditions across the Argentine ant’s expanded range, yet this variation would largely conflict with the considerably extended nestmate recognition based on CHC uniformity. To shed light on these seemingly contradictory selective pressures, we attempt to decipher which CHC classes enable adaptation to such a wide array of environmental conditions and contrast them with the overall CHC profile uniformity postulated to maintain nestmate recognition. n-Alkanes and n-alkenes showed the largest adaptability to environmental conditions most closely associated with desiccation, pointing at their function for water-proofing. Trimethyl alkanes, on the other hand, were reduced in environments associated with higher desiccation stress. However, CHC patterns correlated with environmental conditions were largely overriden when taking overall CHC variation across the expanded range of L. humile into account, resulting in conserved colony-specific CHC signatures. This delivers intriguing insights into the hierarchy of CHC functionality integrating both adaptation to a wide array of different climatic conditions and the maintenance of a universally accepted chemical profile.

Gas chromatograph coupled with a mass selective detector (GC: 7890A; MS: 5975C; Agilent Technologies, Santa Clara, California, USA) operating in electron impact mode. The injection was performed in a split/splitless injector in the splitless mode with a temperature of 250°C. Separation of compounds was performed on a fused silica capillary column (DB-5MS, 30 m x 0.32 mm x 0.25 μm, Agilent J&W GC columns, Santa Clara, California, USA) with a temperature program starting from 80°C for 5 min and increasing by 80°C per min to 200°C, followed by an increase of 5°C per min to 325°C which was held for 3 min. Helium with a constant flow of 1.8 ml per min was used as carrier gas.

Peak area integration and calculation was performed using the data analysis software “Enhanced Chemstation”, G1701EA, Version E.02.02 (Agilent Technologies, Santa Clara, California, USA). Peaks were automatically integrated with an initial area reject of 0, an initial peak width of 0.017, and an initial threshold of 13. Shoulder detection was turned off. All automatically integrated peak areas were visually inspected and where necessary corrected by manual integration. CHCs were identified according to their retention indices, diagnostic ions, and mass spectra.