Relative geographic range of sibling species of host damselflies does not reliably predict differential parasitism by water mites

Abstract

BackgroundOne of the main challenges in evolutionary parasitology is to determine the factors that explain variation among host species in parasitism. In this study, we addressed whether host phylogeny or ecology was important in determining host species use by water mites. Parasitism (prevalence and intensity) by Arrenurus water mites was examined in relation to geographic distribution of host damselflies from sibling species pairs. In addition, the likelihood of putative mite species parasitizing both species of a host species pair was explored.ResultsA total of 1162 damselflies were examined for water mites across four sites in Southeastern Ontario. These damselflies represent ten species (five closely related host species pairs) in the Coenagrionidae. Only two of the five species pairs showed near significant or significant differences in prevalence of infection by mites. In one of those species comparisons, it was the less widespread host that had higher water mite prevalence and in the other species comparison, the less widespread host species had lower water mite prevalence. Only one of the five pairs showed a significant difference in intensity of infection; intensity was higher in the species with a smaller geographic distribution. Based on the COI barcode, there were nine water mite clades (OTU) infecting these ten host species. Three Arrenurus OTUs may be host monospecific, four OTUs were specific to a given host species pair, and two OTUs infected at least three host species. Host species in each species pairs tend to share at least one of the Arrenurus OTU. No striking differences in mite species diversity were found among species in any species pair. Finally, the Arrenurus examined in this study appear to be ecological specialists, restricted to a particular type of habitat, parasitizing few to many of the host species present in that site or habitat.ConclusionsAlthough differences in levels of parasitism by water mites exist for some closely related hosts species, no such differences were found between other related host species. Differences in geographic range of related host species does not reliably explain differential levels of parasitism by water mites.

Host phenology, geographic range size and regional occurrence explain interspecific variation in damselfly–water mite associations

“…Similarly, the prediction of the geographic range hypothesis was supported in a study comparing two species of Calopteryx in Finland (Ilvonen et al 2011). In contrast, the geographic range hypothesis was not supported in two studies comparing gregarine and water mite parasitism in several pairs of closely related coenagrionid damselflies where the less widespread species of the species pairs had higher parasitism levels (Mlynarek et al 2012(Mlynarek et al , 2013). In the current study based on an increased number of non-phylogenetically paired host species, we find some support for the geographic range hypothesis.…”

“…Homologous sequences from four Arrenurus sp. individuals collected from Nehalennia gracilis and N. irene damselflies (Mlynarek et al ) and four Enallagma ebrium (Mlynarek et al ) were included in the COI alignment, and seven water mite species were selected from GenBank to serve as outgroups (AB530314, JX838402, JX836526, JX835088, JN018105, JN018109, AB530311).…”

Explaining Interspecific Variation in Susceptibility and Resistance to Parasitism in Damselflies

“…The geographic range of damselfly hosts explained in part the prevalence and intensity of gregarine endoparasites . In contrast, host geographic range was a poor predictor of Arrenurus water mite prevalence and intensity when comparing pairs of closely related damselfly host species from single sites (Mlynarek et al 2013).…”

“…Evaluating ecological patterns of resistance to parasitism might aid in the explaining the differences in parasitism between hosts. Studies with closely related odonate host species have documented differential levels of immunity (Kanost and Gorman 2008) and resistance to parasites , Nagel et al 2011, Mlynarek et al 2013, Rynkiewicz et al 2013) but the link between immunity and resistance has not been clear (Nagel et al 2011).…”

“…In this study, I tested the extent to which geographic range, regional representation, local abundance, phenology and body size of host species are good predictors of prevalence, and intensity of water mite parasitism and, predictors of proxies of species richness of mite parasites. My study was restricted to damselflies of the family Coenagrionidae, but I expand upon Mlynarek et al (2013) by examining more host species across many sites and by using parasite species diversity as an additional measure of parasitism. I tested the generality of regional representation, local abundance and body size in explaining interspecific variation in parasitism, because they have been shown to be important factors in vertebrate-parasite systems (Poulin 2007).…”