期刊
AMERICAN NATURALIST
卷 177, 期 2, 页码 E43-E53出版社
UNIV CHICAGO PRESS
DOI: 10.1086/657685
关键词
maintenance of sex; fitness; life-history evolution; cost of males; Brachionus calyciflorus; parthenogenesis
资金
- Fonds zur Forderung der wissenschaftlichen Forschung [P20735-B17]
- Austrian Science Fund (FWF) [P 20735] Funding Source: researchfish
- Austrian Science Fund (FWF) [P20735] Funding Source: Austrian Science Fund (FWF)
The ubiquity of sexual reproduction is an evolutionary puzzle because asexuality should have major reproductive advantages. Theoretically, transitions to asexuality should confer substantial benefits in population growth and lead to rapid displacement of all sexual ancestors. So far, there have been few rigorous tests of one of the most basic assumptions of the paradox of sex: that asexuals are competitively superior to sexuals immediately after their origin. Here I examine the fitness consequences of very recent transitions to obligate parthenogenesis in the cyclical parthenogenetic rotifer Brachionus calyciflorus. This experimental system differs from previous animal models, since obligate parthenogens were derived from the same maternal genotype as cyclical parthenogens. Obligate parthenogens had similar fitness compared with cyclical parthenogens in terms of the intrinsic rate of increase (calculated from life tables). However, population growth of cyclical parthenogens was predicted to be much lower: sexual female offspring do not contribute to immediate population growth in Brachionus, since they produce either males or diapausing eggs. Hence, if cyclical parthenogens constantly produce a high proportion of sexual offspring, there is a cost of sex, and obligate parthenogens can invade. This prediction was confirmed in laboratory competition experiments.
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