More than one genotype: how common is intracolonial genetic variability in scleractinian corals?

Abstract

In recent years, a few colonial marine invertebrates have shown intracolonial genetic variability, a previously unreported phenomenon. Intracolonial genetic variability describes the occurrence of more than a single genotype within an individual colony. This variability can be traced back to two underlying processes: chimerism and mosaicism. Chimerism is the fusion of two or more individuals, whereas mosaicism mostly derives from somatic cell mutations. Until now, it remained unclear to what degree the ecologically important group of hermatypic (reef building) corals might be affected. We investigate the occurrence of intracolonial genetic variability in five scleractinian corals: Acropora florida, Acropora hyacinthus, Acropora sarmentosa, Pocillopora species complex and Porites australiensis. The main focus was to test different genera for the phenomenon via microsatellite markers and to distinguish which underlying process caused the genetic heterogeneity. Our results show that intracolonial genetic variability was common (between 46.6% for A. sarmentosa and 23.8% for P. species complex) in all tested corals. The main process was mosaicism (69 cases of 222 tested colonies), but at least one chimera existed in every species. This suggests that intracolonial genetic variability is widespread in scleractinian corals and could challenge the view of a coral colony as an individual and therefore a unit of selection. However, it might also hold potential for colony survival under rapidly changing environmental conditions.

Contrasting futures for ocean and society from different anthropogenic CO 2 emissions scenarios

“…Most coral species have clearly adapted to warm environments (54,55) although the time scale of adaptation is likely to be long given the relatively lengthy generation times of corals [3 to 100 years (56)]. Recent studies have shown short-term acclimation and adaptation in some fast-growing species (57) and suggested that some genetic mechanisms may allow faster rates of change (58). It is, however, doubtful that corals will be able to adapt quickly enough to maintain populations under most emissions scenarios (56,59,60), especially where temperature keeps increasing over time (RCP4.5 and higher).…”

Climate Change Impacts on Seagrass Meadows and Macroalgal Forests: An Integrative Perspective on Acclimation and Adaptation Potential

“…However, they do exist in long-lived seagrasses clones (Reusch and Boström, 2010) and may confer fitness advantages. Interestingly, in corals, genetic heterogeneity has also been observed within clones (Schweinsberg et al, 2015).…”

Do reef corals age?

“…Phenotypically observable mutation rate is similarly high, with 300-500 mutations estimated to accumulate over the lifetime of the colony in Orbicella faveolata (Barfield et al, 2016). High frequencies of somatic mutations have also been proposed to explain significant intra-colonial variability observed in other coral species (Maier et al, 2012;Schweinsberg et al, 2015Schweinsberg et al, , 2016. In addition, significant levels of somatic mutation have been reported in microsatellite loci between ramets within the genet of A. palmata from sites across the Caribbean (Devlin-Durante et al, 2016).…”