Question of Space May Hold Answers to Parasite Diversity

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The theory that diversity begets diversity proposes that the number of parasite species grows as hosts evolve into new species. According to a new article in the Journal of Parasitology, spatial scale is the key to how this diversity increases.

Vol. 102 Issue 5 (October 2016)

Vol. 102 Issue 5 (October 2016)

Individual studies have tested ‘diversity begets diversity’ at extremely divergent spatial scales, but no attempt has been made to integrate the concept of spatial scale into theory supporting this hypothesis.

Journal of Parasitology – Parasites and their hosts often have a positive relationship. As hosts grow and change, so do the parasites that rely on them. What researchers don’t yet understand is how diversity in two such species is linked. A recent study in the current issue of the Journal of Parasitology adds a new element that may change how people look at parasites and the diseases they spread.

Researchers from the University of Michigan and University of Colorado Boulder offer several ideas about why it is difficult to compare the results from studies of host–parasite relationships. Using previously published studies, the researchers tested their theories and suggest a better way to look at relationships between such species.

The theory that diversity begets diversity has been well studied, particularly because it can affect the risk and spread of disease. Parasites depend on their hosts, so the theory proposes that the number of parasite species grows as hosts evolve into new, distinct species. More hosts mean more niches and ultimately more parasite species.

According to the researchers of the study, the missing key to how this diversity increases is the idea of spatial scale. Space refers not just to the boundaries of a study area but also to the opportunities for individuals to interact. When studies do not use the same spatial scale or ignore this factor, comparing the results between studies can be like comparing apples to oranges.

“Individual studies have tested ‘diversity begets diversity’ at extremely divergent spatial scales, but no attempt has been made to integrate the concept of spatial scale into theory supporting this hypothesis,” states Chelsea Wood, corresponding author of the article. She and co-author Pieter Johnson suggest that focusing on space could make it easier to understand the extent to which host richness relates to parasite richness. Studying how many parasite species are added for each host species could help researchers estimate the number of parasite species on Earth and learn more about disease risk and spread.

Although the researchers of this study write that their work raises more questions than it does answers, Wood points out that “this paper is the first to integrate the problem of spatial scale into theory on how host and parasite diversity are linked.” The paper argues that to better understand the diversity relationship between host and parasite, researchers need to test different data in new ways. A new study that looks at the diversity of a single parasite and its host across spatial scales could provide many of the missing answers.

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Caitlyn Ziegler
Allen Press
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