The currency of science

There is a lot of talk within the scientific world about publishing your research. When writing a paper it is important to think about whether the project is publishable, where the story you are working on is worth telling and where would be the best place to publish it so that the story reaches most of the people that will actually be interested in your story.

I have been fortunate recently to have the first of my thesis papers published in a well reputable journal, Ecological Entomology. This paper is entitled “Higher gregarine parasitism often in sibling species of host damselflies with smaller geographical distributions.” My co-authors, Chris Hassall and Mark Forbes (my supervisor), and I wanted to tell an interesting story about damselfly internal parasites. It is now available online at the following link.

I must first make a quick introduction of the associations between damselflies and their most common internal parasites, gregarines. Damselflies and dragonflies or even other insects eat gregarine eggs (for the remaining of this text, I will call damselflies hosts). These start to develop in the gut of the damselfly and are anchored to the host gut wall. Gregarines (Fig. 1) are around 1mm in size. They are one celled organisms that take in the nutrients that the host is digesting. In order to know that a damselfly is infected by a gregarine, you either have to dissect the abdomen of a damselfly or wait to see ‘eggs’ passed in the feces of the host. Dissecting is easier (Fig. 1). Gregarines are very difficult to identify but knowing that they are present is possible.

Fig. 1 Gregarine inside an Enallagma ebrium damselfly abdomen (picture taken by V. Putinsky)

Starting my thesis project, I was interested in seeing whether the size of a species geographic distribution had an effect on levels of parasitism. Previous work with marine fish, rodents and birds of prey has demonstrated that as the size of the geographic distribution increases so does parasite diversity, i.e. the number of parasite species a host species has. I was interested to determine whether this pattern would hold if you did not take how many species of parasites are in a host into account but whether levels of parasitism was also influenced by a host species geographic distribution. By measures of parasitism, I mean prevalence, or the number of host individuals that are infected by a particular group of parasite, and intensity, or the number of parasite individuals in only infected host individuals.

Damselfly-parasite associations have been studied for some time now and I thought it would be a good association to use. For this project, I decided to look at 14 species of damselflies. I grouped them in species pairs, meaning that 2 host species were always more evolutionarily related than the remaining 12 species. At the same time, I chose host species with contrasting geographic distribution sizes. Therefore 7 host species had small geographic distributions and the 7 larger ones. When you superimpose the species pairs onto the size of geographic distributions, I had one species per species pair with a small geographic distribution and the other had a larger one (Fig. 2). I thought that there would be a clear pattern.

Fig. 2 Distribution maps for the Calopteryx species pair. An example of what was used to get the distribution size data. (Maps created by C. Hassall)

I caught the damselflies around the Queen’s University biological station North of Kingston, Ontario during the summer of 2010. Interesting patterns came up. As the title suggests, and contrary to popular belief, host species with smaller geographic distributions tended to have more gregarine parasites (Fig. 3). This of course was not occurring across the board, certain species pairs showed the opposite relationship. Because there was variation in parasitism, I am now able to start looking at why those host species responded differently. These results are not as straight forward as I had hoped but they do allow me to continue telling this story which will, I have no doubt have much intrigue and hopefully a great conclusion.

Fig. 3 Prevalence differences between the species in the species pairs demonstrating the tendency of less widespread species having higher gregarine prevalence. (* represents significant differences in prevalence; reprouced from Mlynarek et al. 2012)


Mlynarek, J.J., Hassall, C. and Forbes, M.R. 2012. Higher gregarine parasitism often in sibling species of host damselflies with smaller geographical distributions. Ecological Entomology 37, 419–425.


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One response to “The currency of science

  1. Pingback: A new paper | Katatrepsis

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