A guide for the validation of DNA based species identification in forensic casework

Method validation is an essential step ahead of applying a method in forensic casework, to ensure the results will be admissible in court. However, unlike mainstream forensic disciplines, wildlife forensic labs often evolve from conservation-oriented units and may not have a strong foundation in generating data within a legal context. As such, the processes and principles of method validation may not be familiar or fully understood. In this paper we describe the process of method validation in a wildlife forensic science context. We provide guidance on the documentation required to take a DNA based method, which has been developed to identify a specific target species, through the validation process so that it is fit for use in forensic casework. This process has been agreed upon among members of the Society for Wildlife Forensic Sciences (SWFS) Technical Working Group (TWG) to illuminate the requirements for both practitioners and academics

Bayesian paternity analysis and mating patterns in a parasitic nematode, Trichostrongylus tenuis.

Mating behaviour is a fundamental aspect of the evolutionary ecology of sexually reproducing species, but one that has been under-researched in parasitic nematodes. We analysed mating behaviour in the parasitic nematode Trichostrongylus tenuis by performing a paternity analysis in a population from a single red grouse host. Paternity of the 150 larval offspring of 25 mothers (sampled from one of the two host caeca) was assigned among 294 candidate fathers (sampled from both caeca). Each candidate father's probability of paternity of each offspring was estimated from 10-locus microsatellite genotypes. Seventy-six (51%) offspring were assigned a father with a probability of >0.8, and the estimated number of unsampled males was 136 (95% credible interval (CI) 77-219). The probability of a male from one caecum fathering an offspring in the other caecum was estimated as 0.024 (95% CI 0.003-0.077), indicating that the junction of the caeca is a strong barrier to dispersal. Levels of promiscuity (defined as the probability of two of an adult's offspring sharing only one parent) were high for both sexes. Variance in male reproductive success was moderately high, possibly because of a combination of random mating and high variance in post-copulatory reproductive success. These results provide the first data on individual mating behaviour among parasitic nematodes