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Free keywords:
inbreeding; parasite fitness; genetic compatibility; genetic variability;
mating systems
Abstract:
Many parasitic helminths exhibit mixed mating systems, and switches between self-fertilization and 24
outcrossing may be influenced by environmental conditions and parasite demography. While inbreeding 25
depression selects against the development of purely self-fertilizing populations, genetic compatibility 26
may contribute to stabilizing mixed strategies. Here we study the effects of inbreeding and genetic 27
compatibility on offspring fitness in the digenean trematode Diplostomum pseudospathaceum, a parasite 28
with a three-host life cycle. Hatching rates and infection success in two intermediate hosts, the freshwa- 29
ter snail Lymnaea stagnalis and the three-spined stickleback, Gasterosteus aculeatus, were used as proxies 30
for parasite fitness. Single trematode clones and combinations of two and three different clones were 31
allowed to reproduce sexually using naïve herring gulls (Larus argentatus) as definitive hosts. The hatched 32
larvae were used to assess the proportion of selfed and outcrossed miracidia by means of microsatellite 33
genotyping. These results were matched with hatching rates and infection success of inbred and 34
outcrossed trematodes in both intermediate hosts. Inbreeding effects were obscured by differences in 35
clone performance. In addition, clones outcrossed to a lesser extent than expected in some experimental 36
pairings, indicating the importance of genetic compatibility.
