Melissopalynological studies of stingless bee tetragonnula travancorica (Apidae: Meliponini)

Abstract

The present investigation entitled “Melissopalynological studies on stingless bee Tetragonula travancorica (Apidae: Meliponini)” was conducted at the Department of Agricultural Entomology, College of Agriculture, Vellayani, during 2017-2020. The objective was to study the foraging activity of stingless bee T. travancorica Shanas and Faseeh and to identify its floral pollen resources occurring in Thiruvananthapuram district. Eighteen locations were selected across the district on the basis of land elevation and composite sampling of pollen and honey was done purposively from hive during the three seasons, viz. Northeast monsoon season (October- December), Dry season (January- May) and Southwest monsoon season (June- September). The collected samples were processed and analysed using standard acetolysis procedure recommended by the International Commission for Bee Botany (Louveaux et al., 1978). The pollen load in honey samples were determined and pot pollen collected during the period was subjected to metabarcoding. Foraging activity of stingless bees in the hive was studied and observations were recorded fortnightly from 0600 hrs to 1800 hrs during all the three seasons from November to August. In the study, out of 115 plant types recorded as foraging sources, 93 were identified. Sixty-seven plants were identified up to the species level, 16 to genus level and 10 up to family level. Important species identified were Cocos nucifera, Mimosa pudica, Mimosa diplotricha, Milletia pinnata, Macaranga peltata, Alternanthera sessilis, Areca sp., Peltophorum pterocarpum, Sweitenia mahagoni, Tridax procumbens, Mikania micrantha, Amaranthus spinosus, Amaranthus viridis, Borassus flabellifer, Ageratum conyzoides, Ceiba pentandra, Passiflora edulis, Caesalpinia echinata, Boerrhavia diffusa, Amaranthus hybridus, Delonix regia, Terminalia arjuna, Psidium guajava, Psidium araca, Momordica charantia, Eucalyptus sp., Glochidion sp. and Syzygium cumini. The most predominant were pollen of Cocos nucifera, Mimosa pudica and Milletia pinnata during all seasons. The secondary pollen types observed were Macaranga peltata, Tridax procumbens, Sweitenia mahagoni, Peltophorum pterocarpum, Amaranthus spinosus, Alternanthera sessilis and Areca sp. Most frequently observed pollen type in honey samples were C. nucifera and M. pinnata whereas C. nucifera and M. pudica were very frequent in pollen samples common to all seasons. The botanical family which had the highest recorded pollen type was Fabaceae (8) followed by Asteraceae (7) and Myrtaceae (7). Metabarcoding of pollen revealed that Amaranthus tuberculatus, A. spinosus, A. caudatus, A. hybridus, A. hypochondriacus, A. palmeri, Malvales sp., Benincasa hispida, Lagenaria siceraria and Muntingia calabura were the predictable candidates as observed by their bit scores and E-value. The total pollen count of honey samples ranged from 27,000 TNP/mL (Group II) to 2, 94,000 TNP/mL (Group III). A marked difference was observed between mid-land and upland and also among locations during both the seasons. The pollen count in midlands was lower during dry season whereas during northeast monsoon season the pollen count in uplands was radically lowered. Foraging activity of stingless bees revealed that the highest activity occurred during March and April (hotter months) while the lowest during December and January (colder months). The maximum number of outgoing and incoming foragers with pollen was recorded during April, March and February whereas, incoming foragers without pollen was highest during March, April and May. The highest average of outgoing foragers and incoming foragers with pollen load was observed during 0900 to 1200 hrs while, in incoming foragers without pollen load, it was from 1000 to 1300 hrs. The ratio of pollen foragers to total incoming foragers was highest during November followed by December and the least during May and June. Thus, melissopalynological studies revealed the presence of 115 foraging sources for T. travancorica in Thiruvananthapuram district while foraging studies revealed maximum foraging activity during hot dry season. The study highlights that the stingless bees exploit diverse floral resources available in their surroundings.