Comparison of the effect of time and preservative on the quality of DNA from pitfall traps.
The aim of this project was to generate evidence to inform best practise guidance for Natural England staff wishing to use DNA metabarcoding to identify invertebrate communities from pitfall trap samples. We wished to determine whether ethanol or propylene glycol should be used as the preservative solution for optimum preservation of invertebrate DNA, considering results and practicalities in the field. We also set out to determine what length of time traps could be left out in the field and still retain high quality invertebrate DNA; and whether the use of 'roofs' over pitfall traps would affect the DNA quality. This report describes a study in which DNA was extracted and analysed from pitfall trap samples collected under different conditions. All samples collected in ethanol and propylene glycol in this study showed good amplification with invertebrate specific primers, with minimal differences in Cq values, demonstrating their suitability for metabarcoding applications. Considering the higher DNA yields; lower degradation; and ease of use in the field (as compared to ethanol), we would recommend the use of propylene glycol for preservation of pitfall trap samples for DNA analysis. DNA metabarcoding has excellent potential for invertebrate identification and monitoring. This study has provided evidence to inform best practise guidance for the setup of pitfall traps to be analysed using DNA metabarcoding techniques.