Abstract
Genetic variation in parasites has important consequences for host–parasite interactions. Prior studies of the ecologically important parasite Metschnikowia bicuspidata have suggested low genetic variation in the species. Here, we collected M. bicuspidata from two host species (Daphnia dentifera and Ceriodaphnia dubia) and two regions (Michigan and Indiana, USA). Within a lake, outbreaks tended to occur in one host species but not the other. Using microsatellite markers, we identified six parasite genotypes grouped within three distinct clades, one of which was rare. Of the two main clades, one was generally associated with D. dentifera, with lakes in both regions containing a single genotype. The other M. bicuspidata clade was mainly associated with C. dubia, with a different genotype dominating in each region. Despite these associations, both D. dentifera- and C. dubia-associated genotypes were found infecting both hosts in lakes. However, in lab experiments, the D. dentifera-associated genotype infected both D. dentifera and C. dubia, but the C. dubia-associated genotype, which had spores that were approximately 30% smaller, did not infect D. dentifera. We hypothesize that variation in spore size might help explain patterns of cross-species transmission. Future studies exploring the causes and consequences of variation in spore size may help explain patterns of infection and the maintenance of genotypic diversity in this ecologically important system.
Highlights
Most parasite species contain substantial diversity (Thompson and Lymbery, 1990), and one of the grand challenges in understanding the evolution of infectious diseases is to understand what promotes this genotype diversity (Metcalf et al, 2015)
Over all parasites isolated from D. dentifera and C. dubia, HS was 0.409 [95% confidence interval (CI): (0.379, 0.422)], but for parasites infecting each host species, HS was lower [D. dentifera HS = 0.291, 95% CI: (0.222, 0.333); C. dubia HS = 0.290, 95% CI: (0.232, 0.324)], indicating lower diversity of genotypes infecting each individual host species
Metschnikowia bicuspidata is a widespread parasite of Daphnia (Green, 1974; Ebert, 2005) with substantial impacts on the ecology (Duffy, 2007; Duffy and Hall, 2008; Penczykowski et al, 2020) and evolution (Duffy and Sivars-Becker, 2007; Duffy et al, 2008, 2012) of its hosts
Summary
Most parasite species contain substantial diversity (Thompson and Lymbery, 1990), and one of the grand challenges in understanding the evolution of infectious diseases is to understand what promotes this genotype diversity (Metcalf et al, 2015). Is genetic variation within parasites common, it is important to the ecology and evolution of host-parasite systems. In other cases, diversity of a parasite is surprisingly low even in systems where the parasite is not thought to have recently invaded new hosts and habitats. One example of this is the ecologically important host-parasite system comprised of the fungus Metschnikowia bicuspidata and its zooplankton (daphniid) hosts, where infections can reach high prevalences (∼60% of the population with late stage infections at the peak of large outbreaks (Shaw et al, 2020)). Research from the 1880s in Europe (Metschnikoff, 1884) and 1970s in the USA (Green, 1974) suggests that M. bicuspidata has likely had a world-wide distribution for centuries
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
