Construction of a robust phylogeny facilitates development of an environmental DNA-based survey tool for the bog hoverfly, Eristalis cryptarum

Abstract

Surveying an endangered species is vital for its successful conservation. The use of environmental DNA (eDNA) as surveying tool for rare and elusive species has gained popularity over recent years. Eristalis cryptarum, commonly known as the bog hoverfly is listed as a priority species on the UK Biodiversity Action Plan, is Critically Endangered and restricted to few sites on Dartmoor National Park. It is widely assumed E. cryptarum have an aquatic, rat-tailed larval stage, as is the case for other closely related species. The larvae however, have never been discovered in the UK in order to determine this. In Chapter 1, using the mitochondrial gene cytochrome c oxidase subunit 1 (cox1), the phylogeny of E. cryptarum is explored. Using molecular data and morphological characteristics, E. cryptarum is placed within the Eristalini tribe, a tribe distinguished by an aquatic, rat-tailed larval stage. This offers further support for the assumption that E. cryptarum possesses an aquatic, rat-tailed larval stage. The use of eDNA as a tool to survey endangered species has been widely used in previous studies and offers a sensitive, non-invasive approach to survey elusive and rare species. Here, larval E. cryptarum eDNA will be screened for in water samples collected from known habitat sites on Dartmoor National Park. Chapter 2 is focused on the development on taxa-specific primer sets and are tested for specificity and sensitivity in preparation for eDNA screening in Chapter 3. Primer sets were designed and developed successfully with high specificity to target taxa and shown to be sensitive through a number of dilution series. The use of an environmental DNA technique to determine the presence or absence of E. cryptarum eDNA in water samples is an exciting alternative to traditional surveying techniques. Chapter 3 explores this, and there was no amplification of E. cryptarum eDNA but a successful amplification of a closely related species, E. arbustorum from water samples where E. arbustorum was known to be present (using E. arbustorum specific primer sets). This suggests the need for further research and optimisation of this method for successful surveying of E. cryptarum using an eDNA methodology.