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Diversity, Distribution and Relative Abundance of Insect Pollinators on Apple Crop in Shimla Hills of Western Himalaya India

Diversity, distribution and relative abundance of various insect visitors of apple crop was investigated and carried out by collecting flower visitors in different orchards located at Padola (2200 m), Kalzar (2514 m) and Jarol (2648m) in Shimla hills of Western Himalaya. Insect diversity studies showed that apple flowers were visited by 41 species of insects belonging to 5 orders and 16 families of class Insecta. Of these, 13 species belonged to Hymenoptera, 17 to Diptera, 8 to Lepidoptera, 2 to Coleoptera and 1 to order Thysanoptera. Analyses of data on relative abundance of different insect visitors revealed that Indian hivebee, A. cerana was the most abundant insect visitor to apple flowers in all the three experimental orchards i.e. Padola (29.23%), Kalzar (29.43%) and Jarol (28.82%). European honey bee, A. mellifera (18.59%, 17.23% and 16.74%) and Bombus tunicatus (2.02%, 2.04% and 1.98%) were other important hymenopterans at Padola, Kalzar and Jarol orchards. Besides, hymenopterans, dipterans also constituted an important group of insect pollinators.


Introduction
Pollination provides an essential ecosystem service that contributes to the maintenance of biodiversity and ensures the survival of plant species including crop plants. For one out of every three bites eaten, one can thank a bee, butterfly, bat, bird or other pollinator. Any loss of biodiversity is a matter of public concern, but losses of pollinating insects may be particularly troublesome because of the potential effects on plant reproduction and hence on food supply security. Many agricultural crops and natural plant populations are dependent upon pollination and often on the services provided by wild, unmanaged, pollinator communities (Free, 1993;Kluser and Peduzzi, 2007).
It is estimated that about 85% of the world's flowering plant species depend upon animals, mostly insects for pollination (Ollerton et al., 2011) and the total annual economic value of crop pollination worldwide is about $153billion (Gallai et al., 2009). Mattu (2013) emphasized that flower-visiting insects provide an important ecosystem function to global crop production through their pollination services. The rapid spread of human habitation is affecting the available natural habitats through urbanization and other land-use practices, putting pressure on ecosystem services delivered by wild pollinators. Other agronomic practices like manuring, pesticides, fertilizers etc. are quite cost effective and these may not yield the desired results without the use of managed and unmanaged pollinators for enhancing the productivity levels of different crops by pollination.
In recent years, apple has emerged as the leading cash crop amongst temperate fruit crops in Himalayan belt. It alone accounts for 48% of area under all fruits and 78% of total fruit production. The area covered under apple production increased from 35,076 ha in 1975-76 to 99,564 ha in 2009-10 registering an annual growth of 3.14% during this period (Singh et al., 2012). During the last few years, the production of apple per hectare has come down inspite of increase in area under apple cultivation. So, there is a need for changed strategies and look for other possible inputs such as full use of under-utilized and eco-friendly resources like bee pollination for increasing apple production in state (Verma and Jindal, 1997;Mattu et al., 2012b;Mattu and Mattu, 2013;Mattu, 2014).
Honeybees derive their food in the form of pollen and nectar, which are the raw materials of beekeeping industry. This collection of pollen and nectar from flowering plants by bees is known as 'foraging behavior'. In the Himalayan region Honey bees are the most important pollinators in apple orchards and they form a vast majority of pollinating insects (Free, 1993). However, very little is known about the role of different insect visitors including honeybees in pollinating various horticultural crops in India especially Himachal Pradesh (Mishra et al.,1976;Mattu and Verma, 1985;Verma, 1990;Kumar, 1997;Mattu and Bhagat, 2015). Therefore, present investigation was conducted in order to know the diversity, distribution and relative abundance of different insect species visiting apple crop in Shimla hills of Western Himalaya.

Material and Methods
Research investigations were carried out on diversity, distribution and relative abundance of various insect visitors of apple crop, by collecting them in different orchards located at Padola (2200 m), Kalzar (2514 m) and Jarol (2648 m) of Shimla hills of Western Himalaya. These apple orchards had more than 200 trees belonging to Golden delicious, Red delicious, Royal delicious and Red Gold varieties. All these collections were made during the months of March-April, when the orchards were in full bloom. Almost equal number of working hours were spent in each Licensed Under Creative Commons Attribution CC BY orchard. Relative abundance of different insect visitors was determined in terms of their visits per 500 flowers/10 minutes (Verma and Chauhan, 1985). The observations were recorded during 0900-1000, 1200-1300 and 1500-1600 hours of a day and average counts at these hours gave abundance of an insect pollinator for the particular day (Southwood, 1978). For collection of different insect species, following methods were used: Hand picking; sweeping; beating; aerial netting and aspirator method and standard methods were followed for the preservation of insect pollinators belonging to different orders such as Hymenoptera; Diptera; Lepidoptera; Coleoptera and Thysanoptera (Arora, 1990;Ghosh, 1990;Jonathan, 1990). Pollination data was analysed statistically (Snedcor and Cochran, 1993).

RESULTS AND DISCUSSION
Pollinator diversity studies showed that apple flowers were visited by 41 species of insects belonging to 5 orders and 16 families of class Insecta. Of these, 13 species belonged to Hymenoptera, 17 to Diptera, 8 to Lepidoptera, 2 to Coleoptera and 1 to order Thysanoptera ( These results are in conformity with the earlier observations of Mishra et al. (1976); Verma (1990) and Mattu and Mattu (2010) who also reported that honeybees constituted a major proportion of insect pollinators on apple crop in Shimla hills and wild bees also visited apple flowers in good number. Similarly, Dashad (1989) and Kumar (1997)  Analyses of data on pollinator diversity and relative abundance of insect visitors on apple bloom it is observed that Hymenopterans were most abundant insect pollinators on apple bloom in Shimla hills of Western Himalayas. These results were in accordance with earlier findings of Mattu and Mattu (2007) who also found hymenopterans (78.89%) as the most important insect pollinators on almond bloom, whereas, hymenopterans (44.50%) and dipterans (49.37%) were almost equally abundant on peach bloom in Shimla and Solan hills respectively. Present results also support the recent findings of Mattu and Bhagat (2015) who also found hymenopterans as the most important insect pollinators on apple bloom in Himachal Pradesh.