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Do parasites lower Daphnia hybrid fitness?
Author(s) -
Wolinska Justyna,
Keller Barbara,
Bittner Kerstin,
Lass Sandra,
Spaak Piet
Publication year - 2004
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2004.49.4_part_2.1401
Subject(s) - biology , daphnia galeata , hybrid , daphnia , fecundity , zoology , taxon , cladocera , ecology , population , branchiopoda , botany , demography , crustacean , sociology
In Greifensee (Switzerland), Daphnia galeata × hyalina hybrids cooccur with both parental taxa. Hybrids are the most abundant taxon, suggesting that hybrids have greater fitness. In addition to many known factors that promote hybrids, specific environmental conditions favoring parentals must also exist to explain their cooccurrence. We investigated the influence of the protozoan gut parasite Caullerya mesnili on the D. galeata × hyalina species complex. Up to 22% of the Daphnia population was infected with C. mesnili in October 2002. C. mesnili dramatically reduced the fecundity of its hosts. Only 2% of infected individuals carried eggs compared with 70% in the uninfected group, which suggests that C. mesnili exerts a strong selection pressure. Our results indicate that hybrids were frequently infected, whereas parental D. galeata were almost never infected. We also found genetic variation for infection within hybrids, evidenced by significant differences in clonal composition between the infected and uninfected parts of the taxon. Resistance of D. galeata might counterbalance the greater fitness of hybrids and therefore contribute to the maintenance of coexistence of hybrids and parentals in this lake.