Interspecific variation in damselfly–water mite associations

Submitted by editor on 19 November 2014. Get the paper!

Enallagma ebrium with Arrenurus water mites


Phenology and regional occurrence explain interspecific variation in damselfly-water mite associations

by Julia J. Mlynarek


When near a water body it is easy to spot damselflies perched on grass blades or whizzing past your head.  If you catch one, you may notice it is has little round spheres attached to its thorax or abdomen; those are water mites. If you continue catching damselflies, you will notice that some damselfly species have more water mites attached than other species. Then why are some damselfly species more parasitized than others?

We answered this question by collecting several damselfly species at thirteen sites in southeastern Ontario and southwestern Quebec, which were visited weekly for eight weeks.


Julia Mlynarek collecting damselflies

Our study suggests that host characteristics can, in part, be responsible for the interspecific variation in prevalence, intensity and parasite species richness.

Phenology of a host species, or when that species is most active, explained a lot in terms of parasite prevalence (percent of infected individuals) and intensity (average number of parasites per infected individual). We found that, in temperate North America, species that are most active during peak activity of all damselflies have the highest prevalence and intensity of parasitism.  But a species phenological activity did not tell the whole story; its geographic distribution is also a contributing factor to prevalence and intensity of water mite parasitism. In the case of geographic distribution, species with mid-size ranges tend to have highest levels of parasitism.

We identified the larval water mites using molecular techniques to determine what host character explains parasite species richness in different damselfly species. Regional occurrence (the number of sites a species is present within a region) was by far the strongest predictor of water mite species richness between the damselflies we collected.

So why are some damselflies species more parasitized than others? In the damselfly-water mite associations, it depends on spatial and temporal host characteristics. It is clear that measuring host characteristics at different scales (ecological, geographical and temporal) is important to have an understanding of host-parasite associations.


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