Chimerism is a coalescence of conspecific genotypes. Although common in nature, fundamental knowledge, such as the spatial distribution of the genotypes within chimeras, is lacking. Hence, we investigated the spatial distribution of conspecific genotypes within the brooding coral Stylophora pistillata, a common species throughout the Indo-Pacific and Red Sea. From eight gravid colonies, we collected planula larvae that settled in aggregates, forming 2–3 partner chimeras. Coral chimeras grew in situ for up to 25 months. Nine chimeras (8 kin, 1 non-related genotypes) were sectioned into 7–17 fragments (6–26 polyps/fragment), and genotyped using eight microsatellite loci. The discrimination power of each microsatellite-locus was evaluated with 330 ‘artificial chimeras,’ made by mixing DNA from three different S. pistillata genotypes in pairwise combinations. In 68% of ‘artificial chimeras,’ the second genotype was detected if it constituted 5–30% of the chimera. Analyses of S. pistillata chimeras revealed that: (a) chimerism is a long-term state; (b) conspecifics were intermixed (not separate from one another); (c) disproportionate distribution of the conspecifics occurred; (d) cryptic chimerism (chimerism not detected via a given microsatellite) existed, alluding to the underestimation of chimerism in nature. Mixed chimerism may affect ecological/physiological outcomes for a chimera, especially in clonal organisms, and challenges the concept of individuality, affecting our understanding of the unit of selection.
Bibliographical noteFunding Information:
We thank I.M. Ashkenazi and L. Guttman’s lab (National Center for Mariculture, Eilat) for hospitality and logistical support, the Nature and Parks Authority, Israel, for permits (41424/2016, 41552/2017) and to G. Paz for his help in preparing the illustrations. The study was supported by grants from the AID-MERC (M33-001) to B.R., by the Israeli-French high council for scientific and technological research program (Maïmonide-Israel) to B.R. and by the National Science Foundation (DEB, Grant No. 1839775) to T.L.G. G.G. was supported by a fellowship from BGU-Eilat Campus. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
© 2021, The Author(s).
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