Emergent diversity of an ecologically important parasite group

As organisms that can cause death and disease in their hosts, parasites are forms of life that can have important ecological effects on the host populations that they exploit. Switches in host can occur as parasites jump to new host species in new environments and in the process will adapt their biology. As every different animal is a new potential host, parasites can diversify greatly and huge numbers of uncharacterized parasite species may exist. Each of these parasites could potentially represent a future danger both to human health and ecosystems. This great diversity of parasites is not immediately obvious because of their mainly microscopic and hidden nature, which means that they cannot be easily seen or described without sampling and dissecting hosts. Therefore how many different species of parasites exist and how successfully they transfer to new hosts and habitats are still unknown factors. DNA-based methods represent a rapid and inexpensive way to sample a wide range of biological diversity present in environmental samples, and importantly provide a means to survey previously unsampled microscopic lifeforms. It is now possible to collect a wide diversity of invertebrates and other small animals present in soil, ponds and marine environments and then extract the DNA from all these organisms along with that of their associated parasites and use state of the art gene sequencing technology to sequence the same gene for each parasite in the sample. By studying the diversity of this DNA we can identify the number and diversity of microscopic parasites present in the original sample. Here we will use this strategy to begin to enumerate the number of particular parasite groups in diverse environments, varying in geographic location, season, and including marine, terrestrial and freshwater environments. The group of parasites that we will survey are the microsporidia. These are highly unusual relatives of fungi that are adapted to live inside the cells of a variety of different animals. In humans, microsporidia can cause serious infections in those with seriously impaired immune systems, for example in people in the late stages of AIDS, or recipients of organ transplants. They also infect economically important animals such as farmed fish and honeybees. Microsporidia have been found in all major animal lineages and in all environment types worldwide. Currently over 1200 species of microsporidia are known to exist, though research suggests that large amounts of uncovered species are present in the environment. We intend to sample freshwater, estuarine, marine and soil environments across different seasons and geographic locations and use DNA methodologies to enumerate the distinct molecular types of microsporidia in each sample as a measure of species number. We can then use this data to try to understand: 1) How our current estimates of parasite species numbers compares to actual environmental numbers 2) Whether numbers of microsporidian species vary with geographic location 3) Which environmental factors, for example season, latitude, or environment type are associated with high levels of diversity of microsporidian parasites This type of quantification of different species will enable us to tell how successfully microsporidia have diversified in different environments. It will indicate whether there are particular environments that have allowed these parasites to thrive over evolutionary timescales. By characterising the differences in types of parasites found in different environments we can understand whether climate change or human movement by trade or travel has the potential to introduce new parasites into new areas. This can indicate how much potential there is for microsporidia to cause new infections in humans and wildlife.