Pathogens have got this reproduction thing figured out. Clone yourself and grow populations quickly? Sure. Occasionally reproduce sexually? Absolutely. The have-your-cake-and-eat-it-too reproductive modes among biological lineages that are capable of both sexual and asexual reproduction throw a mighty wrench into a bulk of evolutionary theory.
A new paper in Evolution from Bryan Falk, Rich Glor, and Susan Perkins tests three predictions about these types of lineages using a malarial parasite found in lizards, Plasmodium floridense:
- Cryptic species should exist
- Lineages that clonally reproduce will have low intraspecific genetic variation
- Putative species will be recently diverged
Using a suite of species delimitation techniques, the authors identify 11 putative “species” of P. floridense, buuuut:
The species we delimited may or may not be philosophically sound.
As I’ve (mis)quoted above, these cryptic lineages are tough to classify using any species concept:
Rather than describe the 11 P. floridense species at this time, we hope to initiate dialogue among systematists about the taxonomic issues associated with clonally reproducing species, and to move forward with consensus. A desirable quality of the classification of these species is that species delimitation be objective and repeatable, and philosophically grounded in biology. In the context of our study, it is important to ask whether the species we delimited should be considered species, and we discuss this question in terms of both our analytic approach and species concept.
Each of these separate lineages have relatively low genetic diversity, and the divergence times between them are relatively recent. Together, these results clearly support the conclusion that clonal lineages that are capable of sexual reproduction can have diversity that is flying under the radar.
Knowledge of the factors that determine pathogen diversification is valued at a premium, and taking first steps with pathogens infecting wild hosts is a valuable investment for the future.
Falk, B. G., Glor, R. E., & Perkins, S. L. (2015). Clonal reproduction shapes evolution in the lizard malaria parasite Plasmodium floridense. Evolution. DOI: 10.1111/evo.12683