Phylogenetically conserved host traits and local abiotic conditions jointly drive the geography of parasite intensity

Abstract

1. The role of biotic interactions in shaping species distributions is a cornerstone of biogeographic theory; yet, it remains elusive. Such interactions are more likely to have an influence on organisms with obligate associations, such as hosts and their parasites. Whereas abiotic conditions may affect the abundance and distribution of parasites in ways similar to free-living species, attributes of the host could also play a part. 2. Here, we focus on parasitic water mites and their dragonfly and damselfly hosts, and use a hierarchical Bayesian model to examine the relative influence of the abiotic environment and biotic factors such as local host community structure and individual host characteristics on parasite intensity along a broad-scale environmental gradient. Specifically, we assessed how climate, surrounding vegetation, water chemistry, host community structure as well as the relative abundance and body mass of host species affected the intensity of parasitism on individual hosts along a latitudinal gradient. 3. We found that water chemistry and body mass of the host were the best predictors of variation in parasite intensity among hosts. High parasite intensity was observed in hosts sampled from lakes with high pH, dissolved oxygen and conductivity. Additionally, we found that the intensity of parasitism was strongly influenced by host species identity. In particular, body mass, which shows strong phylogenetic signal, was negatively related to parasite intensity. It may be that larger species, or individuals within species, are more immune to high level of parasitism and/or body mass is correlated with other traits of the host which relate to immunity. 4. Considering both the abiotic environment and attributes of host species is necessary to understand why certain host individuals and locations exhibit more intense parasitism. Amid widespread decline of insect populations worldwide , some of which are attributed to pathogens and parasites, models predicting rates of parasitism in space and time could become an essential tool for guiding management and conservation efforts.

A role for the local environment in driving species‐specific parasitism in a multi‐host parasite system

“…We examined the relationships between parasite prevalence and intensity and host immune function (total PO activity) and five environmental factors (fish density, larval density, prey density, pH, and mean air temperature). We focused on these factors because previous studies have suggested that they can either directly or indirectly shape parasitism in this system (e.g., da Silva et al, 2021;Hasik et al, 2021;LoScerbo et al, 2020;Worthen & Turner, 2015).…”

“…We examined the relationships between parasite prevalence and intensity and host immune function (total PO activity) and five environmental factors (fish density, larval density, prey density, pH, and mean air temperature). We focused on these factors because previous studies have suggested that they can either directly or indirectly shape parasitism in this system (e.g., da Silva et al, 2021; Hasik et al, 2021; LoScerbo et al, 2020; Worthen & Turner, 2015). Full details of sampling procedures for fish density, larval density, prey density, and pH have been previously published (Siepielski et al, 2010), and thus we only briefly summarise them here (full details can be found in the Appendix S1).…”

“…Mites attack when larval damselflies transition into flying adults (Forbes & Robb, 2008;Smith et al, 2010), and the number of mites on a single damselfly ranges from one to >400 (e.g., Worthen & Turner, 2015). As in other studies (LoScerbo et al, 2020;Mlynarek et al, 2013Mlynarek et al, , 2015Worthen & Hart, 2016;Worthen & Turner, 2015), we did not identify mites to species level, as the subgenus Arrenurus is a large and diverse group of cryptic species, and it is unknown how many species parasitise Enallagma. Like Enallagma, Arrenurus mites probably are limited in their dispersal, as they rely on the dispersal ability of their hosts (Bohonak et al, 2004).…”

La ecología de los parásitos zoonóticos en Carnivora

“…En general, las especies con estrategias de alimentación terrestre, presentan más parásitos zoonóticos que las especies de alimentación marina a pesar de más esfuerzo de estudio dedicado a las especies marinas en promedio (según lo determinado por los resultados de búsqueda de temas de Web of Science). Los parásitos que se encuentran en estos grupos de hospederos, podrían esperarse que se agrupen con especies relacionadas filogenéticamente, ya que la transmisión exitosa, depende de los comportamientos del hospedero y las tasas de contacto infeccioso que varían con la ecología funcional [23][24][25][26].…”

The ecology of zoonotic parasites in the Carnivora

“…In general, species with terrestrial foraging strategies have more zoonotic parasites than marine foraging species despite more study effort devoted to marine species on average (as measured by Web of Science topic search hits; data available in Table S3). The parasites found across these host groups may be expected to cluster among phylogenetically related species since successful transmission depends on host behaviors and rates of infectious contact that vary with functional ecology [23][24][25][26]. For instance, foraging behaviors vary widely from strict endotherm predators (e.g., cheetah, family Felidae) to nearly strict herbivores (e.g., giant panda, family Ursidae), which may influence the sources from which zoonotic pathogens are acquired (prey vs. plants).…”