Effects of genotypic diversity on growth and survival of an ecologically important coral

Abstract

Biodiversity loss threatens ecosystems worldwide, but we lack a thorough understanding of how genotypic diversity—as opposed to species diversity—impacts threatened foundation species, such as corals on tropical reefs. Corals of the genus Pocillopora have been important to natural reef recovery and human-assisted restoration in the Pacific. They consistently perform better in polycultures with other coral species than in monocultures, but whether genotypic diversity within a species enhances performance remains untested. We assessed whether increased genotypic diversity of the coral Pocillopora verrucosa (i.e., the number of genetically distinct source colonies per plot) improved growth, reduced tissue mortality, or increased resistance to invasion of competing seaweeds over 3.5 years in experimental plots on reefs in Mo‘orea, French Polynesia. We could detect no significant differences in any of these performance metrics among plots comprised of one, three, six, or nine genotypes. Moreover, when we quantified mitochondrial genetic divergence among genotypes within each plot using mean pairwise nucleotide distance, performance was unrelated to the degree of genetic differentiation represented. Thus, we detected no effect of genotypic diversity on Pocillopora performance. Pocillopora acclimates rapidly to variable physical and biological conditions, which may make genotypic diversity effects less critical for these corals.