Using metabarcoding to compare the suitability of two blood‐feeding leech species for sampling mammalian diversity in North Borneo

Abstract

The application of high-throughput sequencing (HTS) for metabarcoding of mixed samples offers new opportunities in conservation biology. Recently, the successful detection of prey DNA from the guts of leeches has raised the possibility that these, and other blood-feeding invertebrates, might serve as useful samplers of mammals. Yet little is known about whether sympatric leech species differ in their feeding preferences, and whether this has a bearing on their relative suitability for monitoring local mammalian diversity. To address these questions, we collected spatially matched samples of two congeneric leech species Haemadipsa picta and Haemadipsa sumatrana from lowland rainforest in Borneo. For each species, we pooled ~500 leeches into batches of 10 individuals, performed PCR to target a section of the mammalian 16S rRNA locus and undertook sequencing of amplicon libraries using an Illumina MiSeq. In total, we identified sequences from 14 mammalian genera, spanning nine families and five orders. We found greater numbers of detections, and higher diversity of OTUs, in H. picta compared with H. sumatrana, with rodents only present in the former leech species. However, comparison of samples from across the landscape revealed no significant difference in mammal community composition between the leech species. We therefore suggest that H. picta is the more suitable iDNA sampler in this degraded Bornean forest. We conclude that the choice of invertebrate sampler can influence the detectability of different mammal groups and that this should be accounted for when designing iDNA studies.

Occurrence of blood‐feeding terrestrial leeches (Haemadipsidae) in a degraded forest ecosystem and their potential as ecological indicators

“…Furthermore, different biodiversity metrics could be used instead of mammal abundance, such as biomass or evenness, which might be more realistic and/or important for leeches. As previous molecular work has demonstrated, both of our focal species of leech tend to feed preferentially on larger‐bodied mammals, with very little DNA from small mammals detected in their blood meals (Drinkwater et al., ). Therefore, a more nuanced metric of mammalian biodiversity, that considers leech feeding behavior, may yet reveal stronger associations.…”

“…As previous molecular work has demonstrated, both of our focal species of leech tend to feed preferentially on larger-bodied mammals, with very little DNA from small mammals detected in their blood meals (Drinkwater et al, 2018). Therefore, a more nuanced metric of mammalian biodiversity, that considers leech feeding behavior, may yet reveal stronger associations.…”

“…To test whether abundance of available prey influences leech detectability, we used a reduced leech survey dataset to compare the fit of models with and without the inclusion of mammal abundance as a covariate. In this study, we focus on mammals as a measure of available prey, because previous studies conducted in the same area were unsuccessful in detecting any other vertebrate groups in the diets of these two Bornean leech species (Drinkwater et al., ; Schnell et al., ). Firstly, we generated the covariate for mammal abundance from camera traps which had been deployed across the SAFE landscape from 2015 to 2017.…”

“…To test whether abundance of available prey influences leech detectability, we used a reduced leech survey dataset to compare the fit of models with and without the inclusion of mammal abundance as a covariate. In this study, we focus on mammals as a measure of available prey, because previous studies conducted in the same area were unsuccessful in detecting any other vertebrate groups in the diets of these two Bornean leech species (Drinkwater et al, 2018;Schnell et al, 2018 Models were constructed which had the optimal structure without the inclusion of mammals (identified from initial analysis of the full dataset) and with the addition of mammal abundance. AIC values were compared to evaluate whether the inclusion of mammals increases the model fit.…”

Vertebrate diversity revealed by metabarcoding of bulk arthropod samples from tropical forests

“…Since the field of iDNA originated, targeted collection followed by iDNA analyses of gut contents has been carried out on different invertebrate taxa such as leeches (Drinkwater et al, 2019;Pérez-Flores, Rueda-Calderon, Kvist, Siddall, & Oceguera-Figueroa, 2016;Schnell et al, 2018;Weiskopf et al, 2018), sand flies (Kocher, De Thoisy, et al, 2017), blow and flesh flies Hoffmann et al, 2018;Lee, Gan, Clements, & Wilson, 2016;Lee, Sing, & Wilson, 2015;Rodgers et al, 2017;Schubert et al, 2015), mosquitoes (Kocher, De Thoisy, et al, 2017), ticks (Gariepy et al, 2012), marine copepods (Meekan et al, 2017), and shrimps (Siegenthaler et al, 2019). This has offered a new and promising tool to complement traditional vertebrate monitoring methods, something of great value in the ongoing biodiversity monitoring efforts (Bohmann et al, 2013).…”