Estimating effective population size for a cestode parasite infecting three-spined sticklebacks

Area of Science:

• Ecology
• Evolutionary Biology
• Parasitology

Background:

• Estimating contemporary effective population size (Ne) for parasitic species is rare but vital for understanding parasite evolution and host-parasite coevolution.
• Previous research on the stickleback-cestode system suggests external physiographic factors influence parasite genetic variation.

Purpose of the Study:

• To estimate contemporary effective population size (Ne) for the cestode parasite Schistocephalus solidus and its host, the three-spined stickleback (Gasterosteus aculeatus).
• To investigate the factors influencing parasite and host Ne, particularly the role of host attributes.
• To assess the sensitivity of Ne estimates to population genetic structure and connectivity assumptions.

Main Methods:

• Utilized multi-locus microsatellite data to derive single-sample and temporal estimates of Ne.
• Analyzed data from cestode parasites and their stickleback hosts in Alaskan lakes.
• Examined the relationship between host attributes (body length, genetic diversity, infection) and parasite Ne.

Main Results:

• Both parasite and host Ne estimates were small and highly variable, consistent with prior studies.
• Ne estimates were sensitive to assumptions about population genetic structure and connectivity.
• Host attributes such as body length, genetic diversity, and infection intensity were found to shape contemporary parasite Ne, contrasting with previous findings emphasizing external factors.

Conclusions:

• Contemporary effective population size (Ne) in parasitic species is influenced by host-specific factors, including host body length, genetic diversity, and infection levels.
• These host-internal factors play a significant role in shaping parasite Ne, complementing previous research that highlighted external environmental influences.
• Accurate estimation of Ne in host-parasite systems requires careful consideration of both population structure and host-related variables.