Non-lethal DNA extraction methods for genetic analyses of endangered bumble bee species

Abstract

Several North American bumble bees (Hymenoptera: Bombus) are faced with decline as factors such as climate change, pollution, and urbanization threaten their existence, thus raising concern regarding genetic diversity as populations diminish. Consequently, genetic analysis of these susceptible species is essential when considering appropriate conservation efforts. One species, Bombus affinis, has experienced such sharp population declines that it was listed as federally endangered within the United States and Canada. This necessitates methods for collecting genetic samples from bumble bees that do not require euthanizing specimens or removing legs. A previous pilot study used 50 mL conical tubes fitted with sugar water soaked swabs to passively collect genetic material from Bombus affinis. Approximately 50% of the 63 samples obtained contained usable amounts of DNA. To further improve this technique, samples were collected from Bombus impatiens using two non-lethal, minimally-invasive DNA extraction methods that can be applied to declining and endangered species. In one method, bumble bee thoraxes were swabbed directly to collect hairs from the immobilized bumble bees, whereas the second technique involved the passive DNA collection method utilized in the pilot study. The results of these two techniques were compared using PCR and gel electrophoresis to determine which of these methods, direct swabbing or passive DNA collection, works best for gathering genetic samples without causing unnecessary harm to susceptible and endangered species. It was concluded that the passive technique resulted in distinguishable DNA approximately 1.8 times more consistently than the active technique and is the better option among these methods.