Introduction

Zoophilous pollination by diverse animal pollinators is very important in flowering plants. About 87 of 115 important food crops of the world depend on animal pollination (Kevan 1999; Steffan-Dewenter & Westphal 2008). Insects pollinate an estimated 70% of flowering plants (Schoonhoven et al. 1998), of which the bee community (family Apidae) is the most important and efficient pollinators (Danforth et al. 2006). Increased flower visitation rate by insects causes more pollen deposits on the stigma, benefitting higher seed setting and better seed quality (Engel & Irwin 2003). Naturally, peak flowering seasons correspond with the highest densities of pollinator taxa (Wolfe & Barrett 1988).

Studies from an ecological perspective reveal landscape level habitat heterogeneity as having strong bearings on sustaining insect pollinators (Verhulst et al. 2004; Roschewitz et al. 2005; Fahrig et al. 2011). Linkages within pollination guilds can be disrupted in crop areas if habitat patches reduction causing increasing distances between nesting and foraging areas (Steffan-Dewenter et al. 2006; Pauw 2007). Most pollinators require a reliable supply of nectar within natural pollinator specific foraging distances to provide sufficient pollinator service and gene flow. Honeybees are known to forage in 1 - 3 km radius from the colony (within 1 km for Apis florea Fabricius, 1.5 km for A. cerana Fabricius and 3 km for A. dorsata Fabricius), although pollination efficiency is at the best between 183 – 275 m (Free 1993; Abrol 2012). Landscape maintenance which focuses on better plant-pollinator interactions and on pesticide-free farming will have much significance in ensuring adequate food supplies for the world (Palma et al. 2015). The more we know about pollinators, plant pollination services and the interactions between agro-ecosystems and pollination management, the more we can understand how to conserve them and manage them to maintain biodiversity, ensure ecosystem health and improve human livelihoods (FAO 2016).

Cucurbitaceae (118 genera, 825 species), members known as cucurbits, is an important family of food crops used as fruits (melons), salads (cucumber, gherkins, long melon), sweets (ash gourd, pointed gourd), pickles (gherkins), desserts (melons). Although widely distributed, cucurbit diversity is more concentrated in tropics and subtropics with hotspots in Southeast Asia, West Africa, Madagascar and Mexico (Schaefer & Renner 2011). India is rich in cucurbits and their wild relatives (31 genera, 94 species including 10 endemics). Cucurbits genus with the highest numbers of species are Trichosanthes (22 species), Cucumis (11 species), Momordica (8 species) and Zehneria (5 species) (Renner & Pandey 2013). Honeybees are considered the most efficient pollinator for cucurbit (Grewal & Sidhu 1979).

This study on cultivation of mixed crop of cucurbits in the monsoon period conducted in Utttara Kannada, district of South Indian west coast, is important because it relates to high production of pesticide free, good quality and wholesome gourds from a relatively small area by indigenous farmers. The undulating terrain borders the foothills of the Western Ghat mountain ranges. The cultivators are indigenous subsistence farmers of Halakkivokkal community who depends on traditional farming techniques, cattle manure and leaf manure. The rural landscape has rich biodiversity despite being in the vicinity of the densely populated municipal town and villages. Although cucurbits are grown year-round in India, studies on pollination during monsoon are needed in Southwest India when cucurbit cultivation is at the peak.

The study was aimed at documenting diversities of pollinator insects, their visitation timings and frequencies on cucurbits i.e. Cucumis sativus L. (cucumber), Cucumis pubescens Willd. (Mangalore gourd), Momordica charantia L. (bitter gourd), Trichonsanthes anguina L. (snake gourd) and Luffa acutangula L. (Roxb.) (ridge gourd). This study also presented the role of diverse elements of a traditional landscape in sustaining cucurbit pollinators and the synchronism of the pollinators with the varying flowering schedules of respective crops.