FTIR SPECTROSCOPY ON TAXONOMIC FACILITIES FOR AQUATIC INSECTS: A CASE STUDY ON Noterus clavicornis (DE GEER, 1774)

Species identification is one of the major challenges facing the field of insect taxonomy, the taxonomic group with the greatest diversity in the living world. Because molecular techniques are highly costly, local researchers are often forced to rely solely on morphological identification methods; this undermines the reliability of identifications and highlights the need for alternative and complementary approaches. Although chemotaxonomy and spectral analysis methods have been successfully applied across various scientific disciplines, studies on the effects of climatic differences on subspecies and subvarieties have yet to address the expected gap in the literature. In that respect; based on morphological analyses of N. clavicornis (De Geer, 1774) specimens, a PCA of FTIR spectra from samples collected at different elevations (>2,000 m and 0–700 m), using 60-data-point sliding windows with 10-point shifts, revealed that both groups share the O–H/N–H stretching vibrations at ~3,300 cm⁻¹, the Amide I–II regions at 1,650–1,550 cm⁻¹, and the fingerprint region. However, in samples collected at elevations above 2,000 m, a significant decrease in intensity and band shifts were observed, particularly in the amide bands and in the fingerprint region below 1,000 cm⁻¹, indicating adaptations in cuticle composition and protein/lipid conformation related to elevation. Based on this study, spectral profiling shows promising potential as a complementary tool for taxonomy. It is recommended that future PCA-based spectral comparisons be conducted across broader taxonomic groups and with repeated sampling to distinguish between controversial subspecies and ecotypes.