Molecular diet studies of water mites reveal prey biodiversity

to chironomid larvae and oligochaetes. Future experiments may apply the techniques demon- strated here to water mites living in more stagnant waters, also found on Belle Isle and known to have a plethora of water mite species (pers. obs.). Given that mosquitoes are vectors of many human diseases (malaria, Zika, West Nile virus, etc.) and therefore among the most harmful insects known, the predatory behavior of water mites, along with the ability of Lebertia larvae to parasitize adult mosquitoes [42], indicate that the negative impacts of water mites on mos- quitos may be an important ecosystem service provided by water mites [12]. Other ecosystem services provided by water mites include their potential roles in protecting local species from invasive species and their potential uses as bioindicator species. Water mites have been described as useful in containing an invasion of water boatman insects in waters of the Iberian Peninsula [10]. Some species of the Dipteran larvae Megaselia (prey item for the mite illustrated in Fig 6E) are known as scuttle flies and their larvae are known to inhabit water filled containers and wet areas in urban habitats [43]. They are of interest due to their ability to infest human corpses [43]. Comparably, previous work has investigated the potential use of water mites as a forensic tool for determining post-mortem timelines of corpses in aquatic habitats [44]. Water mites also represent a potentially important bioindicator of water quality for which studies have been conducted in Central America and Europe [45–47].

A 1989 review by Proctor and Pritchard [5] was the last comprehensive work reviewing the diet of water mites. This seminal work was based on the literature available at the time on water mite diets and included some original observations by the authors as well. However, their review is over 30 years old and an update is due. They stated that beyond laboratory observation, very few “feasible alternatives” were available [5]. With the advent of next-genera- tion sequencing, we have upgraded water mite diet studies and propose to extend these studies beyond the Lebertia genus on which the present study focused. Indeed, initial comparisons to Arrenurus (e.g., Fig 6) already showed interesting differences and confirmation of ostracods in their diet [5, 34, 48]. Conclusions We predict that expanding similar research on other water mite genera will result in a signifi- cant body of evidence that would support the importance of water mite predatory behavior in freshwater ecosystems. Their food web importance may have been largely overlooked in past literature and research, viz.: a survey of species-level DNA barcodes for Great Lakes inverte- brates in 2015 listed water mites as “nil” in the public databases [49]. Sampling reports on groups in ecological studies often just group water mites in the “other” category or simply “Acari”, diminishing their potential importance at species or even generic level by omission. Since then, we have improved this database, highlighting the great diversity of water mites in

several Great Lakes sites [2, 20]. Given the predator-prey interactions that the present work reveals, this update on current knowledge of water mites prey in the Great Lakes region may help gain increased recognition of these organisms in food web dynamics and a greater appre- ciation of their ecosystem services. Supporting information S1 Table. Water mite specimens with dates of collection and gut contents. (PDF) S2 Table. Non-mite DNA in water mites from nature. (PDF) PLOS ONE Prey DNA diversity in water mites PLOS ONE | https://doi.org/10.1371/journal.pone.0254598 July 29, 2021 15 / 18