DOI: 10.6078/d1ft43
title: Data from: Desiccation resistance and micro-climate adaptation: cuticular hydrocarbon signatures of different Argentine ant supercolonies across California

description: 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.
description: 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.