Abstract
BackgroundInbreeding depression is an important evolutionary factor, particularly when new habitats are colonized by few individuals. Then, inbreeding depression by drift could favour the establishment of later immigrants because their hybrid offspring would enjoy higher fitness. Rotifers are the only major zooplanktonic group where information on inbreeding depression is still critically scarce, despite the fact that in cyclical parthenogenetic rotifers males are haploid and could purge deleterious recessive alleles, thereby decreasing inbreeding depression.Methodology/Principal FindingsWe studied the effects of inbreeding in two populations of the cyclical parthenogenetic rotifer Brachionus plicatilis. For each population, we compared both the parental fertilization proportion and F1 fitness components from intraclonal (selfed) and interclonal (outcrossed) crosses. The parental fertilization proportion was similar for both types of crosses, suggesting that there is no mechanism to avoid selfing. In the F1 generation of both populations, we found evidence of inbreeding depression for the fitness components associated with asexual reproduction; whereas inbreeding depression was only found for one of the two sexual reproduction fitness components measured.Conclusions/SignificanceOur results show that rotifers, like other major zooplanktonic groups, can be affected by inbreeding depression in different stages of their life cycle. These results suggest that haplodiploidy does not purge efficiently deleterious recessive alleles. The inbreeding depression detected here has important implications when a rotifer population is founded and intraclonal crossing is likely to occur. Thus, during the foundation of new populations inbreeding depression may provide opportunities for new immigrants, increasing gene flow between populations, and affecting genetic differentiation.
Highlights
Inbreeding depression, or the decrease in fitness due to mating between relatives, is an important ecological and evolutionary phenomenon, which has been widely studied from multiple perspectives, such as population genetics, mating system evolution or conservation biology, and for a broad range or organisms [1,2]
The relationship between inbreeding depression and gene flow has emerged as a relevant topic to explore in the case of planktonic invertebrates inhabiting lakes and ponds, due to the population genetic structure detected for these organisms through molecular studies
The results of this study show that inbreeding depression affects several fitness components of B. plicatilis life cycle
Summary
Inbreeding depression, or the decrease in fitness due to mating between relatives, is an important ecological and evolutionary phenomenon, which has been widely studied from multiple perspectives, such as population genetics, mating system evolution or conservation biology, and for a broad range or organisms [1,2]. De Meester et al [11], extending the founding effects hypothesis of Boileau et al [12], proposed the Monopolization Hypothesis to explain this paradox According to this hypothesis, founding effects would persist due to (1) dilution, after population founding, of new immigrants in a large number of residents and (2) selection against immigrants arriving in a locally adapted population. Rotifers are the only major zooplanktonic group where information on inbreeding depression is still critically scarce, despite the fact that in cyclical parthenogenetic rotifers males are haploid and could purge deleterious recessive alleles, thereby decreasing inbreeding depression
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