Exploring the hidden diversity of winter-emerging Chironomidae (Insecta: Diptera)

Abstract

Chironomidae are a diverse family of flies found on every continent, including Antarctica. As immatures they occupy streams, rivers, lakes, and wetlands and emerge as terrestrial adults. They are biological indicators of water quality and have species-specific tolerance to pollution and disturbances. At least 5,000 species are described, however, projections estimate 20,000 chironomids when including cryptic and yet to be defined species. Cryptic species are one of two or more biological groups that are morphologically identical to one another, are incapable of interbreeding, and are genetically distinct. Driftless Area groundwater-dominated trout streams of southeastern Minnesota provide perfect habitat for cryptic chironomid diversity. During winter, these streams remain open and ice-free all season long because of constant inputs of relatively warm groundwater (~9° C), providing a stable environment in favor of morphological stasis, making the identification of closely related species difficult. Diamesa mendotae Muttkowski and D. nivoriunda Fitch are two commonly encountered winter-emerging chironomids of the Driftless Area. I used molecular methods to explore genetic diversity of these two winter-emerging flies. Cryptic winter-emerging chironomid identification will help sustain trout habitat conservation, create more accurate freshwater management practices, and advance our knowledge of Dipteran evolution.