Insect Functional Guilds in the Flowering Canopy of Myristica Fatua in a Lowland Swamp, Central Western Ghats, India

Abstract

Little is known of canopy insects and pollinators of the nutmeg family (Myristicaceae), despite its being a common pantropical tree family and a commercially-grown spice. To address this lack of knowledge, an assessment was made of the insect fauna associated with the canopy of Myristica fatua (Myristicaceae), an endemic tree species inhabiting the rare and endangered lowland 'Myristica' swamps of the south and central Western Ghats of India. Yellow Sticky Traps were hung in tree canopies to record insect diversity. Insect visitors encountered during the flowering period of Myristica fatua were classified based on their functional role. The captured arthropod fauna was characterised by an abundance of parasitic, predatory, herbivorous and gall-making insects of Chalcidoidea, Platygastroidea, Bethyloidea, Ceraphronoidea, Dolichopodidae, Empididae and Cicadellidae, and a scarcity of beetles. The exclusive gall-making hymenopterans of Cynipidae formed one of the largest insect families in the canopy of M. fatua. The faunal assemblage appeared to be a subset of the entire insect fauna associated with the tree species, as sticky traps leave out the apterygote, sedentary and large insects, and a higher turnover in the insects at the family level could be expected during the fruiting season of the tree. The study highlights the importance of canopy arthropods and their functional roles in community structure.

Pollination of Myristica and Other Nutmegs in Natural Populations

“…Until then, the only study that reported small diverse insects in a nutmeg pollinator guild was the one on Neotropical Virola koschnyi [31]. In Myristica fatua, thrips (Thysanoptera: Phlaeothripidae and Thripidae) and beetles (Coleoptera: Curculionidae, Cleridae, Cucujidae, Cantharidae and Silvanidae) were found to be potential pollinators [52].…”

“…With beetles, pollination is often combined with feeding on stigmatic secretions, anthers and pollen, staminodia, and perianth parts (phytophagy) [50]. Clearly, considerable overlap of functional guilds exists on tropical tree species, and relatively small, simple flowers of trees such as nutmegs can interact with a range of potential insect pollinators [52].…”