BEE POLLEN AS INDICATOR OF FLORAL DIVERSITY: A STUDY USING SOLITARY AND SOCIAL BEES
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Date
2018-10-01
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
A study involving pollen collected by solitary and social bees to assess floral
diversity was carried out during 2015-2017 at GKVK. Flowering phenology and rewards
offered (Nectar/pollen) were recorded for a total of 158 plant species in the study area.
Reference pollen slides were prepared for all species and microphotographs were made.
Pollen sampled from nests of Apis cerana and Megachile spp. were identified using
reference pollen slides which represented 77 species. Floral preference by social and
solitary bees differed significantly. Apis cerana being polylectic, foraged on a diverse
flora and collected pollen from 67 species representing 29 families among these Cocos
nucifera, Eucalyptus and Peltophorum were the most abundant species and their
frequency ranged between 30 to 70 per cent. Whereas, megachilids collected pollen from
21species of only eight families, Fabaceae (>95 %) was the dominant one contain
Crotalaria juncea, Peltophorum pterocarpum, Cajanus cajan, Dolichos lablab and
Millettia pinnata were the most dominant species preferred by megachilids. There was an
overlap of only eight species between Apis and Megachile species. There was a negative
relation (r = -0.44) with floral diversity in the field and pollen grain diversity in the bee
nests. Which may be because of preference by bees for pollen collection from certain
species of flowering plants? To test this hypothesis, plant species visited by bees was
filtered and correlated with the pollen flora in the nests. Such an analyses showed a
positive linear relationship (r = 0.37) between available flora and pollen diversity in the
bee nests. Further, seasonality in pollen collection showed that wet season had strong
relation (r = 0.63) between nest and corresponding field flora followed by summer (r =
0.58) and winter (r = 0.45) seasons.