A study of abundance and diversity of flower-visiting insects on marigold (Tagetes erecta L.) and sunflower (Helianthus annuus L.) at Rajshahi University Campus, Rajshahi, Bangladesh

Abstract

Sunflowers and marigolds hold cultural and commercial significance while serving as important nectar sources for insects and contributing to ecosystem services. This study examined flower-visiting insect abundance, diversity and distribution in sunflower and marigold gardens at Rajshahi University Campus, Bangladesh. In sunflower gardens, we identified six orders, eight families, and twelve species of flower-visiting insects. Marigold gardens comprised six orders, eleven families, and fourteen species of insects. Hymenoptera (57.89%) and Diptera (45.71%) were the most abundant insect orders in sunflower and marigold, respectively. Apidae and Syrphidae were the predominant families in both gardens, with a combined share of 71.93% and 57.14% of the counted insects, respectively. The most dominant species was A. dorsata and E. quinquestriatus in sunflower and marigold garden, respectively. Notably, three species of flower-visiting insects were recorded as the most common visitors both in sunflower (A. dorsata, A. cerana, and Eristalis sp.) and marigold (A. dorsata, Eristalis sp., and E. quinquestriatus) gardens according to their abundance. Shannon's diversity index indicated medium biodiversity in both gardens (2.09 and 2.42), attributed to certain species' abundance. Additionally, both gardens exhibited high species richness (Menhinick index, 1.59 and 1.67) and similar individual distributions (Pielou's index, 0.84 and 0.92).