Comparing the different iDNA samplers for biomonitoring
A PERMANOVA test and further visualization of the dissimilarity matrix
using NMDS (k = 2; stress = 0.17) show that the gamma diversity did not
differ significantly based on iDNA source (p-value = 0.23) (Fig. 5).
Although there was no statistically significant separation in the gamma
diversity found using the different iDNA methods, a site-by-site
comparison of the alpha diversity found with each iDNA method does not
support substantial overlap of the vertebrate communities revealed by
each iDNA source at the site-level (Fig. 5). Although carrion flies
revealed the greatest gamma diversity, when comparing species presence
at a site across iDNA datasets, we found that there were many species
absences in the carrion fly data at sites where sandflies or mosquito
samplers recorded a species presence (Appendix S1: Fig. S4). Carrion fly
data missed 181 of the 213 species occurrences from the sandfly data and
42 of the 63 total species occurrences from the mosquito data when
examined at the site-level (Appendix S1: Fig. S4). Arrowed vectors show
that the significant species in the ordination (p-value <
0.001) were also the most abundant in each iDNA dataset, and thus these
species likely drive the separation in the vertebrate communities at
sites as described by the different iDNA samplers (Fig. 5). These
significant, non-human vertebrate species include cattle (highest RAI in
carrion fly data), dog (highest RAI in mosquito data), nine-banded
armadillo (highest RAI in sandfly data), capuchin, lesser anteater, and
turkey (second highest RAI in mosquito data). This sampler bias was
confirmed by our analysis of the most abundant species in each of the
iDNA datasets which revealed the differing feeding associations of each
insect group (Fig. 6) and we found that these abundant species were
responsible for many of the site-level mismatches between the iDNA
samplers (Appendix S1: Fig. S4). Additionally, we determined that humans
were the primary feeding target of mosquitos (Fig. 6) and human DNA
accounted for more than 80% of the total sequence reads in the mosquito
iDNA dataset.