Morphometric and Genetic Variations Among Stingless Bees Across Varied Altitudes

Abstract This study investigated morphological and genetic diversity among stingless bees from 17 feral nests across India. Adult worker bees, preserved in 70% ethanol, were analyzed using 14 morphometric characters and Principal Component Analysis (PCA). Head length (HL) ranged from 1.08–1.51 mm, head width (HW) from 1.56–1.77 mm, and antennal length (AL) from 1.25–2.06 mm. Forewing length (FL) and width (FW) varied from 3.12–4.0 mm and 1.2–1.56 mm, respectively, with higher values in Coimbatore and Shillong samples. Hind tibial length (HTL) and width (HTW) showed significant variation (HTL: 1.06–1.60 mm; HTW: 0.27–0.55 mm), proving useful for population differentiation. PCA revealed two-character groups: WL2, AL, FL, HW, and FW (PCA1), and HTL, HTW, and hind basitarsus width (PCA2), driving variation. Morphological traits correlated with altitude; HW, HL, AL, FL, FW, and hamuli number increased with elevation, while leg characters decreased. Shillong samples exhibited the greatest morphological divergence.The mitochondrial COX-I primer was used to amplify the genomic DNA of 3 out of 17 stingless bee samples collected from different regions of India, as only the samples from Coimbatore, Thrissur, and Shillong exhibited significant morphological variations.Mitochondrial COX-I gene sequencing of Coimbatore, Thrissur, and Shillong samples confirmed genetic distinctions. Coimbatore and Thrissur samples showed 92% nucleotide similarity with Tetragonulairidipennis (Thrissur) and 87–89% with Punjab specimens, suggesting conspecificity. The Shillong sample, with only 79–80% similarity to these and 96% to Trigona sp., likely represents a distinct species, showing closer affinity (83–86%) to stingless bees from Brazil, Mexico, Madagascar, and Germany than to T. iridipennis.