Biosystematics studies on stingless bees (Apidae : Meliponini) of India

Abstract

The study entitled ‘Biosystematic studies on Stingless bees (Apidae: Meliponini) of India’ was carried out at the College of Agriculture, Vellayani, during 2019-2023 to study the stingless bee diversity in India through morphological and molecular characterisation and document the reproductive biology of Tetragonula travancorica. Extensive sampling was done, and a total of 70 samples were collected from 22 States and 2 Union Territories of India. Samples were collected from domesticated as well as feral colonies by post and field visits. Thirty-four samples were collected through the post and 36 samples were collected through field visits among which, 50 samples were collected from feral colonies and 20 samples from domesticated colonies. 47 per cent of the feral colonies were collected from building basements, 33% from tree hollows, 11 % from rock crevices and 6% from pipes. The samples were processed and preserved for the study of external morphological characters like general shape, size, colour, pilosity, characters of wings, head and thorax. Measurements were made with a calibrated ocular micrometer and pertinent ratios were worked out. Three fifty specimens out of the 70 populations of stingless bee workers were examined. Male genitalia was dissected as per standard protocol and male metasomal sternum 5 and sternum 6 were examined and studied wherever males could be collected. 31 morphological measurements were used in the Principal Component Analysis (PCA) revealing three clusters corresponding to three genera of stingless bee populations viz., Tetragonula, Lisotrigona and Lepidotrigona, identified based on the key to the genera. Species identity was confirmed based on the characters of male genitalia, metasomal sternum and comparative morphometric ratios, obtained from the available literature. Diagnosis of all identified species and detailed descriptions of the new species are provided. The samples collected from all over India could be identified as T. srikantanathi, T. callophyllae, T. travancorica, T. ruficornis, T. shishirae, T. shubhami, Lepidotrigona arcifera and Lisotrigona chandrai. Two putative new species have been identified from Tamil Nadu and Andaman and Nicobar Islands. T. callophyllae was identified from Goa which is the first report of this endangered stingless bee from outside Kerala. Males of T. travancorica were described for the first time. The reproductive biology of T. travancorica was studied using an acrylictopped wooden hive box of 12x4x4 inch size. The length, width, shape and colour of egg and brood cells were recorded. The average length and width of the eggs were found to be 0.88mm and 0.32 mm respectively. The eggs were oval shaped and their colour ranged from transparent to light white. The average length and width of the brood cells were found to be 4mm and 3mm. The brood cells had an oval shape and their colour ranged from dark brown to whitish brown. T. travancorica was found to have an egg period of 4-5 days, a larval period of 18-19 days and a pupal period of 20- 24 days. The total development period was found to be 42-48 days. The oviposition time was found to be 4-7 seconds and the brood cell closing time was found to be 4-6 minutes. Molecular barcodes of the two putative new species and T. callophyllae were generated. Twenty-five gene sequences of stingless bees were obtained based on which, a phylogenetic tree was derived. It showed that the Indian population of stingless bees formed 2 main clades. The first clade included populations belonging to the Genus Tetragonula. The second main clade forms two subclades. The first subclade included T. callophyllae and Lisotrigona chandrai indicating a common ancestor. The second subclade again forms two clusters in which the first includes the populations of stingless bees from Andaman and Nicobar Islands including the putative new species from Andaman and Nicobar Islands. The second cluster includes the population of stingless bees representing the genus Lepidotrigona indicating the presence of a common ancestor. The stingless bees of India comprise 27 species placed in 3 genera. A checklist of Stingless bees in India is provided. The study treated 8 species under 3 genera, 2 putative new species, a new distributional record of T. callophyllae from Goa and a description of males of T. travancorica for the first time. The reproductive biology of T. travancorica was documented. Morphological and molecular characterisation was attempted and a phylogenetic tree was derived and PCA was carried out to clarify the present status of stingless bee taxonomy