Abstract
We investigated the occurrence of intracolonial genetic variability (IGV) in Pocillopora corals in the southwestern Indian Ocean. Ninety‐six colonies were threefold‐sampled from three sites in Reunion Island. Nubbins were genotyped using 13 microsatellite loci, and their multilocus genotypes compared. Over 50% of the colonies presented at least two different genotypes among their three nubbins, and IGV was found abundant in all sites (from 36.7% to 58.1%). To define the threshold distinguishing mosaicism from chimerism, we developed a new method based on different evolution models by computing the number of different alleles for the infinite allele model (IAM) and the Bruvo's distance for the stepwise mutation model (SMM). Colonies were considered as chimeras if their nubbins differed from more than four alleles and if the pairwise Bruvo's distance was higher than 0.12. Thus 80% of the IGV colonies were mosaics and 20% chimeras (representing almost 10% of the total sampling). IGV seems widespread in scleractinians and beyond the disabilities of this phenomenon reported in several studies, it should also bring benefits. Next steps are to identify these benefits and to understand processes leading to IGV, as well as factors influencing them.
Highlights
Since the publication and the scientific recognition of the synthetic theory of evolution (Huxley, 1942), natural selection is recognized as the main engine of evolution
Mosaicism refers to organisms that are subject to intra‐organismal genetic modifications [e.g., so‐ matic mutations, mitotic recombination, mitotic gene conversion (Otto & Hastings, 1998; Youssoufian & Pyeritz, 2002), or gene du‐ plications (Santelices, 1999)], while chimerism designates a single organism resulting from the fusion or exchange of genetically dis‐ tinct parts from different organisms (Rinkevich & Weissman, 1987)
This study of intracolonial genetic variability (IGV) highlighted the existence of the phenomenon in high rates in different populations of Pocillopora corals from the southwestern Indian Ocean
Summary
Since the publication and the scientific recognition of the synthetic theory of evolution (Huxley, 1942), natural selection (i.e., the pres‐ ervation of beneficial individual differences or variations and the disappearance of those that are deleterious in a given environment; Darwin, 1859) is recognized as the main engine of evolution. These results should help understanding IGV and the processes leading to it in corals, as well as the potential benefits of having multiple geno‐ types in a context of declining coral reefs
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