The Significance of Genotypic Diversity in Coral Competitive Interaction: A Transcriptomic Perspective

N Andrade Rodriguez,D J Miller,A Moya,I R Cooke,R Jones

doi:10.3389/fevo.2021.659360

Abstract

Competitive interactions shape coral assemblages and govern the dynamics of coral ecosystems. Although competition is an ecological concept, the outcomes of competitive interactions are ultimately determined by patterns of gene expression. These patterns are subject to genotypic variation on both sides of any interaction. Such variation is typically treated as “noise”, but it is sometimes possible to identify patterns within it that reveal important hidden factors in an experiment. To incorporate genotypic variation into the investigation of coral competitive interactions, we used RNA-sequencing to study changes in gene expression in a hard coral (Porites cylindrica) resulting from non-contact competition experiment with a soft coral (Lobophytum pauciflorum). Hard coral genotype explained the largest proportion of variation between samples; however, it was also possible to detect gene expression changes in 76 transcripts resulting from interaction with the soft coral. In addition, we found a group of 20 short secreted proteins that were expressed as a coordinated unit in three interacting Porites-Lobophytum pairs. The presence of this secretion response was idiosyncratic in that it could not be predicted based on polyp behaviour, or the genotype of hard or soft coral alone. This study illustrates the significance of individual variation as a determinant of competitive behaviour, and also provides some intriguing glimpses into the molecular mechanisms employed by hard corals competing at a distance.

Highlights

Competition is an important ecological interaction, especially in highly productive tropical systems such as rainforests and coral reefs where it is a driver of ecosystem dynamics (Connell et al, 2004; Álvarez-Noriega et al, 2018)
Visible competitive strategies of corals include: overtopping to starve competitors of light; deployment of mesenteric filaments to externally digest a competitor; and elongation of polyps or development of sweeper tentacles to enable contact followed nematocyst discharge [reviewed by Lang and Chornesky, 1990; Chadwick and Morrow, 2011; Yosef et al, 2020). These physical signs are reliable indicators of competition when competitors are in contact, it is clear that a wide range of reef taxa including scleractinian corals, octocorals, sponges, and algae (Coll and Sammarco, 1983; Sammarco et al, 1983; Fearon and Cameron, 1996; Koh and Sweatman, 2000; Chadwick and Morrow, 2011) all produce toxins that could mediate competitive interactions without close contact
In this study we explore the transcriptomic response of Porites cylindrica, a hard coral, to competition with Lobophytum pauciflorum, a soft coral

Summary

Introduction

Competition is an important ecological interaction, especially in highly productive tropical systems such as rainforests and coral reefs where it is a driver of ecosystem dynamics (Connell et al, 2004; Álvarez-Noriega et al, 2018). Visible competitive strategies of corals include: overtopping to starve competitors of light; deployment of mesenteric filaments to externally digest a competitor; and elongation of polyps or development of sweeper tentacles to enable contact followed nematocyst discharge [reviewed by Lang and Chornesky, 1990; Chadwick and Morrow, 2011; Yosef et al, 2020) These physical signs are reliable indicators of competition when competitors are in contact, it is clear that a wide range of reef taxa including scleractinian corals, octocorals, sponges, and algae (Coll and Sammarco, 1983; Sammarco et al, 1983; Fearon and Cameron, 1996; Koh and Sweatman, 2000; Chadwick and Morrow, 2011) all produce toxins that could mediate competitive interactions without close contact. This bias could lead to underestimates of key competitive interactions, especially those for which non-contact competition is the primary mode

Methods

Results

Conclusion