Relationship between phylogeny and immunity suggests older Caribbean coral lineages are more resistant to disease.

Jorge H Pinzón C,Ernesto Weil,Laura D Mydlarz,Joshuah Beach-Letendre,Christian R Voolstra

doi:10.1371/journal.pone.0104787

Jorge H Pinzón C, Ernesto Weil + Show 3 more

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https://doi.org/10.1371/journal.pone.0104787

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Abstract

Diseases affect coral species fitness and contribute significantly to the deterioration of coral reefs. The increase in frequency and severity of disease outbreaks has made evaluating and determining coral resistance a priority. Phylogenetic patterns in immunity and disease can provide important insight to how corals may respond to current and future environmental and/or biologically induced diseases. The purpose of this study was to determine if immunity, number of diseases and disease prevalence show a phylogenetic signal among Caribbean corals. We characterized the constitutive levels of six distinct innate immune traits in 14 Caribbean coral species and tested for the presence of a phylogenetic signal on each trait. Results indicate that constitutive levels of some individual immune related processes (i.e. melanin concentration, peroxidase and inhibition of bacterial growth), as well as their combination show a phylogenetic signal. Additionally, both the number of diseases affecting each species and disease prevalence (as measures of disease burden) show a significant phylogenetic signal. The phylogenetic signal of immune related processes, combined with estimates of species divergence times, indicates that among the studied species, those belonging to older lineages tend to resist/fight infections better than more recently diverged coral lineages. This result, combined with the increasing stressful conditions on corals in the Caribbean, suggest that future reefs in the region will likely be dominated by older lineages while modern species may face local population declines and/or geographic extinction.

Highlights

Immune defenses are critical for species success on ecological and evolutionary time scales [1,2,3]
Phylogenetic reconstruction and time of divergence Sequences of the 28S rDNA region for three corals were generated and in each case these newly sequenced species clustered according to current taxonomy; Meandrina jacksoni with its sister species M. meandrites, Pseudodiploria strigosa with Diploria labyrinthiformis among the robust corals and Siderastrea radians with Porites spp. in the complex corals (Figure 1)
The genera Orbicella and Montastraea originated,105 Mya, with Orbicella radiating between,17 and,7 Mya (Figures 1 and 2). This allowed the sampled lineages to be grouped into older (S. radians, P. porites, P. astreoides, D. cylindrus, M. meandrites and M. jacksoni) and modern (M. aliciae, M. angulosa, D. labyrinthiformis, P. strigosa, M. cavernosa, O. faveolata, O. annularis and O. franksi) lineages

Summary

Introduction

Immune defenses are critical for species success on ecological and evolutionary time scales [1,2,3]. New sets of genetic, biological and/or environmental conditions are encountered making it necessary for emerging species to trade off costs and benefits within and between traits [4], including those related to immunity [5]. The evolutionary importance of immune traits in corals has not yet been evaluated. In other organisms such as fleas [17], termites [18] birds [19,20], and vertebrates in general [21], immune traits are related to phylogeny. A recent taxonomic reorganization [22] facilitates assessment of trait variation and their relationship to life-history

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