Testing the Mating System Model for the Evolution of Parasite Complex Life-Cycles Grant uri icon


  • Parasites can have complex life cycles that involve two or three different host species. Why such complex life cycles persist has long puzzled biologists. This research project will test the theory that the complex life cycles of parasites are maintained or generated by the need to avoid inbreeding, i.e., mating with relatives. It will specifically test whether inbreeding has negative effects on fitness, such as reduced survival or reproduction. The study will be made a parasitic fluke species that has some populations that require three hosts and other populations that require only two hosts. This variation in number of hosts presents an ideal opportunity to test an important mating system model in evolutionary theory. The results will also provide key insights into infectious disease transmission relating to the potential for parasites to infect new host species. The project provides research opportunities and training for graduate and undergraduate students in the fields of parasitology and population genetics. Undergraduates from under-represented groups will be recruited from the Texas A&M Regents Scholars (low income, first generation students) program and Louis Stokes Alliance for Minority Participation. This project will test the mating system model, which proposes that parasite mating systems maintain or generate complex life cycles, specifically that the cost of losing a host is to increase inbreeding. The project has two major aims. Aim 1 will test the underlying assumption of the model that a more complex life cycle will have less inbreeding compared to a simpler life cycle. Aim 2 will test the prediction of the model that inbreeding depression is not manifested when evolving a simpler life cycle. To address these questions, population genetic comparisons will be made within and between species in the trematode genus Alloglossidium. This study system provides an opportunity to test the mating system model because of its among-population variation in life cycle complexity. Populations will be compared for the amount of inbreeding and its potential association with fitness reductions. The results will have an impact on models of evolution concerning host-parasite life cycles and fitness.

date/time interval

  • 2017 - 2020