Multiple species-specific molecular markers using nanofluidic array as a tool to detect prey DNA from carnivore scats

Development and validation of a DNA-based multi-species biomonitoring toolkit using a high-throughput qPCR platform: A case study of Irish shellfish species

Biomonitoring of marine life has been enhanced in recent years by the integration of innovative DNA-based approaches, which offer advantages over more laborious techniques (e.g. microscopy). However, trade-offs between throughput, sensitivity and quantitative measurements must be made when choosing between the prevailing molecular methodologies (i.e. metabarcoding or qPCR/dPCR). Thus, the aim of the present study was to demonstrate the utility of a microfluidic-enabled high-throughput quantitative PCR platform (HTqPCR) for the rapid and cost-effective development and validation of a DNA-based multi-species biomonitoring toolkit, using larvae of 23 commercially targeted bivalve and crustacean species as a case study. The workflow was divided into three main phases: definition of (off-) target taxa and establishment of reference databases (PHASE 1); selection/development and assessment of molecular assays (PHASE 2); and protocol optimization and field validation (PHASE 3). 42 assays were eventually chosen and validated. Genetic signal not only showed good correlation with direct visual counts by microscopy but also showed the ability to provide quantitative data at the highest taxonomic resolution (species level) in a time- and cost-effective fashion. This study developed a biomonitoring toolkit, demonstrating the considerable advantages of this state-of-the-art technology in boosting the developmental testing and application of panels of molecular assays for the monitoring and management of natural resources. Once developed, this approach provides a cost and time-effective alternative compared to other multi-species approaches (e.g. metabarcoding). In addition, it is transferable to a wide range of species and will aid future monitoring programmes.

Molecular analysis of scats revealed diet and prey choice of grey wolves and Eurasian lynx in the contact zone between the Dinaric Mountains and the Alps

A comprehensive understanding of the dietary habits of carnivores is essential to get ecological insights into their role in the ecosystem, potential competition with other carnivorous species, and their effect on prey populations. Genetic analysis of non-invasive samples, such as scats, can supplement behavioural or microscopic diet investigations. The objective of this study was to employ DNA metabarcoding to accurately determine the prey species in grey wolf (Canis lupus) and Eurasian lynx (Lynx lynx) scat samples collected in the Julian Alps and the Dinaric Mountains, Slovenia. The primary prey of wolves were red deer (Cervus elaphus) (detected in 96% scat samples), European roe deer (Capreolus capreolus) (68%), and wild boar (Sus scrofa) (45%). A smaller portion of their diet consisted of mesocarnivores, small mammals, and domestic animals. In contrast, the lynx diet mostly consisted of European roe deer (82%) and red deer (64%). However, small mammals and domestic animals were also present in lynx diet, albeit to a lesser extent. Our findings indicate that the dietary habits of wolves and lynx are influenced by geographical location. Snapshot dietary analyses using metabarcoding are valuable for comprehending the behaviour and ecology of predators, and for devising conservation measures aimed at sustainable management of both their natural habitats and prey populations. However, to gain a more detailed understanding of wolf and lynx dietary habits and ecological impact, it would be essential to conduct long-term genetic monitoring of their diet.

Establishment of a fecal DNA quantification technique for rare and cryptic diet constituents in small mammals

DNA-based approaches have highly improved the applicability of dietary studies aimed at investigating ecological processes. These studies have provided direct insights into, otherwise difficult to measure, interactions between species and trophic levels, food web structure and ecosystem functioning. However, despite these advances, DNA-based methods have been struggling to accurately quantify the whole breadth of diet constituents because of methodological biases, such as amplification bias and digestive processes. This study is, to our knowledge, the first diet study that used droplet digital PCR to quantify diet constituents. We manipulated the diet of wild caught wood mice (Apodemus sylvaticus) by feeding them with a known amount of small vegetable seeds (onion and carrot) and quantified the DNA traces of these diet constituents in fecal samples. The sensitivity of the technique combined with the control on the experimental design allowed mitigation of methodological bias. We were able to accurately determine DNA concentrations of small vegetable seeds in the diet of wood mice. Quantification of target DNA demonstrated significant differences in DNA content when one vs. five seeds were consumed. These differences remained significant when the age, sex, and other diet constituents of the mice were altered. Different DNA markers, targeting different parts of the chloroplast, influenced onion DNA detectability. However, all onion and carrot markers showed higher DNA content for higher seed numbers. Overall, the sensitive DNA based approach developed in this study allows for minimally-invasive quantification of small diet constituents in feces, which would otherwise be undetectable with traditional methods.