Characterizing Billbug (Sphenophorus spp.) Seasonal Biology Using DNA Barcodes and a Simple Morphometric Analysis

Abstract

Billbugs (Sphenophorus spp.) are a complex of grass-feeding weevil species that reduce the aesthetic and functional qualities of turfgrass. Effective billbug monitoring and management programs rely on a clear understanding of their seasonal biology. However, our limited understanding of regional variation in the species compositions and seasonal biology of billbugs, stemming primarily from our inability to identify the damaging larval stage to species level, has hindered efforts to articulate efficient IPM strategies to growers. We used a combination of DNA barcoding methods and morphometric measures to begin filling critical gaps in our understanding of the seasonal biology of the billbug species complex across a broad geographic range. First, we developed a DNA barcoding reference library using cytochrome oxidase subunit 1 (COI) sequences from morphologically identified adult billbugs collected across Indiana, Missouri, Utah and Arizona. Next, we used our reference library for comparison and identification of unknown larval specimens collected across the growing season in Utah and Indiana. Finally, we combined our DNA barcoding approach with larval head capsule diameter, a proxy for developmental instar, to develop larval phenology charts. Adult COI sequences varied among billbug species, but variation was not influenced by geography, indicating that this locus alone was useful for resolving larval species identity. Overlaid with head capsule diameter data from specimens collected across the growing season, a better visualization of billbug species composition and seasonal biology emerged. This approach will provide researchers with the tools necessary to fill critical gaps in our understanding of billbug biology and facilitate the development of turfgrass pest management programs.

Overcoming life stage‐centric biases illuminates arthropod diversity, systematics and biology

“…However, many of the critical life‐history niches occupied by insects are populated by their immature stages, the portion of life during which most of their growth and development occurs, and this is equally true, if less well‐appreciated, in other arthropod groups (e.g., oribatid mites; Norton & Ermilov, 2014). Further, when sampling is for whatever reason limited in time, many life stages whose period of activity is brief, synchronized or limited to a particular temporal window will be missed (Rodriguez‐Soto et al, 2021). Similarly, males and females of many species may differ considerably in abundances, activity period, behaviour and longevity (Cordellier et al, 2020; Kirkendall, 1993; Sielezniew et al, 2020; Smith et al, 2019; Williams et al, 2022).…”