Noninvasive sampling, of faeces and hair for example, has enabled many genetic studies of wildlife populations. However, two prevailing problems common to these studies are small sample sizes and high genotyping errors. The first problem stems from the difficulty in collecting noninvasive samples, particularly from populations of rare or elusive species, and the second is caused by the low quantity and quality of DNA extracted from a noninvasive sample. A common question is therefore whether noninvasive sampling provides sufficient information for the analyses commonly conducted in conservation genetics studies. Here, we conducted a simulation study to investigate the effect of small sample sizes and genotyping errors on the precision and accuracy of the most commonly estimated genetic parameters. Our results indicate that small sample sizes cause little bias in measures of expected heterozygosity, pairwise FST and population structure, but a large downward bias in estimates of allelic diversity. Allelic dropouts and false alleles had a much smaller effect than missing data, which effectively reduces sample size further. Overall, reasonable estimates of genetic variation and population subdivision are obtainable from noninvasive samples as long as error rates are kept below a frequency of 0.2. Similarly, unbiased estimates of population clustering can be made with genotyping error rates below 0.5 when the populations are highly differentiated. These results provide a useful guide for researchers faced with studying the conservation genetics of small, endangered populations from noninvasive samples.

13DNA recovery and extraction efficiencies are key considerations for trace DNA 14 interpretation in casework, but prior studies have tended to focus on assessing these 15 for body fluids rather than trace DNA. This study therefore examined the recovery and 16 extraction of trace DNA using different collection methods from a range of non-porous 17 surfaces relevant to crimes including homicides, terror attacks, and wildlife poaching. 18 Direct extraction of DNA from solutions of a known concentration revealed absolute 19 extraction efficiencies of ~82 %. When DNA was extracted from swabs seeded with 20 the DNA solution, a similarly high efficiency of ~85 % was achieved from nylon-flocked 21 swabs, with a lower efficiency of ~55 % from cotton swabs. However, when DNA was 22 recovered from non-porous surfaces with swabs, ~55 % of DNA was still recovered 23 from plastic knife handles, but lower efficiencies were achieved from the other 24 substrates, particularly metal cable. Varied and poor recovery was observed using 25 mini-tapes and requires further investigation. These results demonstrate that >50 % 26 recovery efficiency of trace DNA is achievable with both swab types, although recovery 27 rates may be affected by surface type and/or practitioner experience.

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