How has metabarcoding been used for conservation in terrestrial systems? A systematic review

Metabarcoding, a methodology associating DNA barcoding and next-generation sequencing, is largely used for the identification of species and for inferences on ecosystem diversity. This technique only became possible with the proliferation of next-gen sequencing, with the term first defined in 2012. Although other reviews have been done focusing on the use of metabarcoding and eDNA, none to our knowledge have focused solely on systematically reviewing studies focused on terrestrial systems and conservation. To identify patterns and gaps in the literature on metabarcoding, we performed a quantitative and qualitative analysis based on an exhaustive search on the Web of Science. Our results indicate that although we frequently assume eDNA and metabarcoding go together, there are many more applications for metabarcoding in terrestrial conservation. Here, we show the distribution of topics involving metabarcoding across taxa. We found insect barcodes are often used in metabarcoding involving diet studies for insectivorous species. We highlighted the gaps for the different subjects that metabarcoding can be applied across taxa, identifying potential research opportunities that, if fulfilled, can lead to significant scientific contributions. Additionally, we stress that metabarcoding can be an extremely useful tool in insect conservation, potentially saving researchers time and resources in insect diversity studies, allowing them to address unique questions about insect conservation that wouldn’t be possible without metabarcoding.