Abstract
Traits that influence reproductive success and contribute to reproductive isolation in animal and plant populations are a central focus of evolutionary biology. In the present study we used an experimental approach to demonstrate the occurrence of environmental effects on sexual and asexual reproduction, and provide evidence for sexual plasticity and inter-clonal fertilization in laboratory-cultured lines of the sea anemone Aiptasia diaphana. We showed that in A. diaphana, both asexual reproduction by pedal laceration, and sexual reproduction have seasonal components. The rate of pedal laceration was ten-fold higher under summer photoperiod and water temperature conditions than under winter conditions. The onset of gametogenesis coincided with the rising water temperatures occurring in spring, and spawning occurred under parameters that emulated summer photoperiod and temperature conditions. In addition, we showed that under laboratory conditions, asexually produced clones derived from a single founder individual exhibit sexual plasticity, resulting in the development of both male and female individuals. Moreover, a single female founder produced not only males and females but also hermaphrodite individuals. We further demonstrated that A. diaphana can fertilize within and between clone lines, producing swimming planula larvae. These diverse reproductive strategies may explain the species success as invader of artificial marine substrates. We suggest that these diverse reproductive strategies, together with their unique evolutionary position, make Aiptasia diaphana an excellent model for studying the evolution of sex.
Highlights
Traits that influence reproduction in animal and plant species have been a central focus of evolutionary biology since Darwin
Asexual reproduction in sessile Anthozoa is important as it provides a means of rapid colonization of a new habitat, as well as providing a means for supplying multiple copies of genotypes that have already proven successful under the prevailing conditions [2]
Under the experimental conditions of this study, asexual reproduction allowed the quick establishment of founding sea anemone populations especially during summer temperature and photoperiod conditions The observed increased rate of pedal laceration in A. diaphana under summer temperature and photoperiod conditions, when compared to the rate under winter conditions, suggests that metabolic components affected by differences in irradiance and/or water temperature, may play a key role in regulating asexual propagation in this species
Summary
Populations of organisms that rely on asexual reproduction are characterized by the number of genetic individuals (genets) being lower than the number of actual individuals (ramets) in an area [3] At times such local populations may be asexual products of single clones. If this is the case, that the possibility of fertilization occurring within a genet or clone (defined here as self-fertilizing or ‘‘selfing’’) may be an important reproductive option for such organisms. The evolution of these species may be enhanced by the meiosis and recombination that occur during sexual reproduction [4,5,6] while asexual reproduction may enhance their successful occupation of new spaces [7]. Genetic variability may be attained via either reproductive isolation or possible hybridizations [10]
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