Species diversity of stingless bees and pollen food sources in Lai Nan subdistrict Wiang Sa district, Nan province

Stingless bees are pollinators that play an important role in the pollination of many crops and endemic plants. This study determined the species diversity and pollen food sources of stingless bees in the Chulalongkorn University Forest and Research Station at Lai Nan subdistrict, Wiang Sa district, Nan province. Stingless bees were collected from September 2010 to August 2011 in deciduous and deciduous - dipterocarp forests. Five genera and six species of stingless bees from the total of 145 nests were found: Tetragonilla collina, Tetrigona apicalis, Tetrigona melanoleuca, Homotrigona fimbriata, Lepidotrigona terminata and Tetragonula pagdeni. Species diversity of stingless bees was low (J’ = 0.125). Tetragonilla collina was the dominant species in this area (C= 0.684). Stingless bees were found in four different types of nesting sites. Tetragonilla collina was found nesting in termite nests and underground, whereas Tetrigona melanoleuca, Homotrigona fimbriata and Lophotrigona terminata nested in live tree hollows. Tetrigona apicalis built their nests in live tree hollows, dead trees and wooden poles. Dipterocarpus tuberculatus, Irvingia malayana, Pterocarpus macrocarcus, Shorea obtuse and S. siamensis were nested by stingless bees. In some cases two species were found sharing the same nesting site. The pollen samples collected by two species of Tetragonilla collina and Tetrigona apicalis were acetolyzed and the pollen types were identified. A total of 59 pollen types were identified in the samples, with the represented 21 families being: Asteraceae (5 pollen types), Caesalpinioideae (4 pollen types), Poaceae (3 pollen types), Convolvulaceae, Euphorbiaceae, Lythraceae, Malvaceae, Mimosaceae (two pollen types each), Apiaceae, Anacardiaceae, Amaranthaceae, Apocynaceae, Bombacaceae, Boraginaceae, Hypericaceae, Myrtaceae, Passifloraceae, Rosaceae, Sapindaceae, Solanaceae, Tiliceae (one type each). Twenty - five pollen types could be identifield and thirty - four pollen types could not be identifield. The number of pollen types and number of flowering plants were not related. The number of pollen food sources collected by Tetragonilla collina and Tetrigona apicalis were 51 and 22, respectively.