Diversity of insect visitors/ pollinators
Sarpagandha flowers (Fig 1) attracted 17 species of insects. Out of these, Lepidopterans were the major floral visitors comprising from three families
viz., Papilionidae (
Papilio demoleus and
Papilio polytes), (Fig 2) Pieridae (
Eurema hecabe,
Pieris sp.,
Anaphaeis sp.,
Pieris canidia,
Belenois aurota,
Pieris brassicae and
Colotis etrida and Hesperiidae (
Pelopidas sp.). They were followed in order of diversity by Dipterans from two families
viz., Sarcophagidae (
Sarcophaga sp.) and Syrphidae (
Eristalinus obscuritarsis) and two species from two families of Hymenoptera
viz., Vespidae (
Polistes olivaceus) and Apidae (
Amegilla zonata) (Fig 3) and Coleopteran from family Coccinellidae (
Coccinella septempunctata). Out of 17 insects all were top foragers except
A. zontata which was side forager (Table 1). These findings are in agreement with those of
Wadhwa and Sihag (2012) who recorded 19 insect species visiting the blossoms of sarpagandha.
Abundance of insect visitors/pollinators
Three insect species are major visitors of sarpangandha bloom. They were belonging to Lepidoptera (2), and Hymenoptera (1). Among Lepidopterans, maximum mean population was of
P. demoleus (3.70 insects/m
2 branch/5min) followed by that of
Pieris sp. (1.23 insects/m
2 branch/5min (Table 2). In Hymenoptera, mean population of
A. zonata was (1.83 bees/m
2 branch/5 min).
Time and week wise, the highest population of
P. demoleus (6.40 insects/m
2 branch/5min) was recorded at 1000h -1200h during 2
nd week of flowering which was significantly different with 1
st week (4.60 insects/m
2 branch/5min) and 3
rd week (5.00 insects/m
2 branch/5min). In case of
Pieris sp. maximum population (2.60 insects/m
2 branch/5min) was recorded at 1000h -12000h during both 2
nd and 3
rd week which was significantly different with 1
st week (1.80 insects/m
2 branch/5min) (Table 2). In case of Hymenoptera, highest population of
A. zonata (4.40 bees/m
2 branch/5min) was recorded at 1000h-1200h during 2
nd week of flowering which was significantly different with 1st week (3.60 bees/m
2 branch/5min) and 3
rd week (3.80 bees/m
2 branch/5min).
Highest pooled mean abundance (3.70 insects/m
2 branch/5min) was recorded in
p. demoleus followed by
A. zonata (1.83 bees/m
2 branch/5min). Lowest pooled mean abundance was recorded in
Pieris sp. (1.23 insects/m
2 branch/5min).
During 2015, similar trend followed as of previous year. Minimum activity of both lepidopterans (
P. demoleus and
Pieris sp.) was recorded between 0600h - 0800h and peak activity was recorded at 1000h – 1200h irrespective of weeks (Table 3). Highest pooled mean abundance (3.47 insects/m
2 branch/5min) was recorded in
P. demoleus followed by
A. zonata (1.85 bees/m
2 branch/5min). Lowest pooled mean abundance was recorded in
Pieris sp. (1.53 insects/m
2branch/5min).
From the present pollination study, it is evident that highest pooled mean abundance of
P. demoleus, Pieris sp. and
A. zonata were reported during 2
nd week of flowering on Sarpagandha flowers. Irrespective of different day hours, significantly maximum number of
P demoleus was recorded from sarpagandha flowers followed by
A. zonata and
Pieris sp. Peak abundance of
P. demoleus,
A.zonata and
Pieris sp. was recorded at 1000h-1200h irrespective of weeks. Minimum abundance was recorded at 0600h -0800h (Table 2 and 3).
Similarly,
Wadhwa and Sihag (2012) observed that
P. demoleus was most abundant pollinator and also found abundance of insect visitors of sarpagandha were low at the time of commencement and cessation of the flowering and high during peak flowering period. These reports were in line with present findings as highest population of all major insect pollinators were recorded during 2
nd week of flowering which was significantly different with 1
st week and 3
rd week.
Charnov, (1976) and
Pyke et al., (1977) stated that during peak flowering more pollen and nectar were available which simultaneously attract more pollinators similar findings were recorded in the present study.
P. demoleus was reported as most abundant pollinator followed by
A. zonata and
Pieris sp. these findings got support from
Wadhwa and Sihag (2012) where lepidopterous insect,
P. demoleus was most abundant followed by
P. brassicae. Similar findings were also reported by
Patil et al., (2008) in pollination studies of brinjal.
L
oose pollen grains on the body of insect visitors/ pollinators during 2014 and 2015
Significant differences were found among the number of loose pollen grains (‘000) sticking to the body of different foragers of three insect species during 2014 (Table 4).
A. zonata (21.50) had the highest loose pollen grains on their body followed by
P. demoleus and Pieris sp. (12.50). In the year 2015, significantly the highest mean number of loose pollen grains (‘000) carried by
A. zonata (23.50) followed by
P. demoleus (15.50) and
Pieris sp. (10.50) (Table 4).
The pooled mean over two years revealed that significantly highest number of loose pollen grains (‘000) entrapped by the
A. zonata (22.50) followed by
P. demoleus (14.00) and
Pieris sp. (11.50). Present findings are in agreement with
Wadhwa and Sihag (2012) who reported that pollen grains carried by the body of
P. demoleus were maximum followed by
P. brassicae in sarpagandha.
Pollination efficiency of major insect visitors/ pollinators
Pollination efficiency of major visitors/pollinators foraging on Sarpagandha flowers revealed that
A. zonata (22.50) entrapped the maximum number of pollen grains (‘000) followed by
P. demoleus (14.00) and
Pieris sp. (11.50) (Table 5). Abundance of
P. demoleus (3.58) was highest followed by
A. zonata (1.84), while the abundance of
Pieris sp. was least (1.38) and the foraging rate of
P. demoleus (23.24) was highest followed by
A. zonata (8.05), while foraging rate of
Pieris sp. was least (6.34).
Pollination index of
P. demoleus (1164.78) was highest followed by
A. zonata (333.27) and
Pieris sp. (100.61). Hence, it was observed that
P. demoleus came out to be most efficient pollinator of Sarpagandha. Other pollinators with relatively lower ranking in pollination efficiency were
A. zonata and
Pieris sp. in descending order. These findings are in agreement with those of
Wadhwa and Sihag (2012) who reported that
P. demoleus was the most efficient pollinator based on the pollination index.
It is concluded that Psychophilous mode of pollination is prevalent due to the tubular flower structure of Sarpagandha. Tubular flowers easily located by lepidopteran pollinators of having long proboscis to draw the nectar from flowers. Small body sized hymenopterans have advantage over large ones due to the tubular structure. In this present study it was reported that long proboscis lepidopterans i.e.,
P. demoleus and small sized hymenopterans i.e.,
A. zonata plays key role in pollination of sarpagandha. Conservation of these pollinators in natural ecosystem is must for pollination of these threatened taxa.
