Searching for phylogenetic patterns of Symbiodiniaceae community structure among Indo-Pacific Merulinidae corals

Abstract

Over half of all extant stony corals (Cnidaria: Anthozoa: Scleractinia) harbour endosymbiotic dinoflagellates of the family Symbiodiniaceae, forming the foundational species of modern shallow reefs. However, whether these associations are conserved on the coral phylogeny remains unknown. Here we aim to characterise Symbiodiniaceae communities in eight closely-related species in the genera Merulina, Goniastrea and Scapophyllia, and determine if the variation in endosymbiont community structure can be explained by the phylogenetic relatedness among hosts. We perform DNA metabarcoding of the nuclear internal transcribed spacer 2 using Symbiodiniaceae-specific primers on 30 coral colonies to recover three major endosymbiont clades represented by 23 distinct types. In agreement with previous studies on Southeast Asian corals, we find an abundance of Cladocopium and Durusdinium, but also detect Symbiodinium types in three of the eight coral host species. Interestingly, differences in endosymbiont community structure are dominated by host variation at the intraspecific level, rather than interspecific, intergeneric or among-clade levels, indicating a lack of phylogenetic constraint in the coral-endosymbiont association among host species. Furthermore, the limited geographic sampling of four localities spanning the Western and Central Indo-Pacific preliminarily hints at large-scale spatial structuring of Symbiodiniaceae communities. More extensive collections of corals from various regions and environments will help us better understand the specificity of the coral-endosymbiont relationship.

Endosymbiont diversity and community structure in Porites lutea from Southeast Asia are driven by a suite of environmental variables

“…Consistent with previous work in Southeast Asia (LaJeunesse et al 2010; Leveque et al 2019;Qin et al 2019), the top three most common types identified in host colonies from all three regions belonged to the genus Cladocopium (Table 1), though the specific composition differed between regions (Fig. 2 & SI Fig.…”

The promotion of stress tolerant Symbiodiniaceae dominance in juveniles of two coral species due to simulated future conditions of ocean warming and acidification

“…Adult G. retiformis are typically dominated by Symbiodiniaceae of the genus Cladocopium (Leveque et al, 2019), however studies conducted on other species propose that under elevated temperature, an increase in more thermally tolerant Durusdinium would be expected (Baker et al, 2004, Berkelmans & van Oppen, 2006, Stat et al, 2013. Similar to adults, G. retiformis juveniles in this study were typically dominated by Cladocopium, but only at T0, although Cladocopium abundances remained higher in juveniles through time under ambient conditions compared to the 2050 and 2100 treatments (Fig.…”

“…2). While Cladocopium C66 has not been previously identified in Goniastrea adults (Leveque et al, 2019), it has been found at low abundance in corals (LaJeunesse et al, 2003). However, C66 has been reported from A. tenuis juveniles, with an increase of C66 over 71 days in the wild (Quigley et al, 2019).…”

A review of soft corals (Octocorallia: Alcyonacea) and their symbionts: Distribution of clades and functionality

“…From 40 soft corals sampled, association was highest with the genus Cladocopium (Clade C). Similarly, the work by Leveque et al (2019) showed Cladocopium as being the most abundant endosymbiont identified in all the Merulinidae corals, accounting for 78.2 % of sequences retained. Clade C strains exhibited more within-clade diversity as compared to the other functional clades (Lesser et al, 2013).…”