Soft coral reproductive phenology along a depth gradient: Can “going deeper” provide a viable refuge?

Liberman, Ronen; Shlesinger, Tom; Loya, Yossi; Benayahu, Yehuda

doi:10.1002/ecy.3760

Cited by 8 publications

(5 citation statements)

References 70 publications

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“…5) along steep environmental gradients can arise from immigrant inviability 44,115 (i.e., heterozygous disadvantage) or strong habitat selection 116 promoting adaptive divergence between locally adapted phenotypes 117 . Similarly, differential temperature regimes across depths may influence the onset of the gametogenesis causing desynchronization of reproductive cycles leading to temporal reproductive isolation across depths 12,118 .…”

Section: Light As a Driver Of Diversity On Reefsmentioning

confidence: 99%

“…Segregation across depth between closely related lineages 8,9 is a particularly promising area of study for understanding the possible role of ecological speciation in light-dependent corals (i.e., with photosynthetic symbionts). Corals living at different depths are exposed to distinct light levels, which affects not only photosynthetic physiology but also many aspects of gamete release and larval settlement cued by light, such as small differences in the timing of spawning, namely a narrow and discrete temporal window (i.e., minutes or hours apart) between species 10 , both of which are well documented for some groups [11][12][13] . However, key remaining questions are: 1) whether genes displaying divergence between nascent depth-segregated species are tied to adaptation to different depths, 2) whether these same genes are linked to reproduction contributing to reproductive isolation, 3) whether natural selection has shaped the evolution of these genes, and 4) whether processes operating within species fuel divergence between species.…”

Section: Introductionmentioning

confidence: 99%

“…/www.ncbi.nlm.nih.gov/gene/?term=110042296 Fig.S5| Example of a cline fitting shape typical of a neutral random locus at intermediate allele frequency across linear distances and among sampling depths. Vertical dashed lines mark collection depth in meters(6,9,12,18,19).…”

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confidence: 99%

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Speciation across depth gradients in reef corals

Prada,

Gómez-Corrales,

González

et al. 2024

Preprint

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Ecological speciation through adaptation to different habitats has been proposed for a variety of terrestrial, freshwater, and marine species. Such divergence of lineages in the absence of strong geographic isolation occurs most readily when the same traits are involved in both adaptation to different ecologies and reproductive isolation. In corals with photosynthetic symbionts and environment-mediated spawning events, adaptation to different light regimes associated with varying depths could provide opportunities for this kind of speciation. Here we show that differences in depth distribution are common in sister lineages of corals from a variety of taxonomic groups and locations. We then explore in detail the molecular drivers behind depth-associated adaptive divergence by documenting patterns of sequence divergence for proteins related to environmental sensing in depth-segregated and light-dependent lineages in the Orbicella species complex. Specifically, we analyzed 1) two ecotypes of Orbicella faveolata that exhibit genetic divergence across a depth gradient that may reflect an incipient recent (~200 Kyr; < 6K generations) speciation event, and 2) two depth-segregated sister species (~500 Kyr), O. annularis and O. franksi, that have been monitored for over two decades and spawn at different times following sunset. Genome-wide variation suggests divergence across depth occurred by adaptation via positive selection on rhodopsin-like G-protein-coupled receptors (GPCRs). These molecules are known to serve as chemo/photo/thermo-receptors mediating environmental transduction signals to enhance physiological adaptation across different environments, while also involved in reproductive isolation via differences in time of spawning in corals. Our study posits a molecular mechanism for the origin of depth-segregated coral species, common across the anthozoan tree of life, in systems in which ecological divergence operates at spatial scales smaller (< 1 km) than their larval dispersal potential, and highlights avenues contributing to generating biodiversity in the sea.

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Section: Light As a Driver Of Diversity On Reefsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Speciation across depth gradients in reef corals

Prada,

Gómez-Corrales,

González

et al. 2024

Preprint

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“…Our results suggest that a temperature increase of up to 6°C for 35 days might not affect the survival of D. erythraeanus, which survived throughout the experiment under the different thermal treatments. However, the experiment was conducted during the autumn, when the ambient temperature was generally lower (mean 5 m: 23.4°C, 45 m: 23.2°C) than the maximum temperature that these sponges experience seasonally during the summer (max temp 5 m: 28.9°C, 45 m: 27.1°C, Shlesinger et al, 2018;Liberman et al, 2022). Therefore, although the moderate temperature treatment (~26°C) exceeded the typical autumn temperatures that these sponges encounter, it was not beyond the temperature range they are exposed to throughout the year.…”

Section: Sponge Physiological Responses Imply a Tolerance To Elevated...mentioning

confidence: 99%

A comparison of mesophotic and shallow sponge holobionts resilience to predicted future temperature elevation

et al. 2023

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Climate change is predicted to have detrimental impacts on sessile invertebrates, including sponges. Mesophotic ecosystems have been suggested to play a major role as refugia for coral reef sponge species, however knowledge regarding the ability of mesophotic sponges to cope with thermal stress is scarce. In this study we compared the response of the sponge Diacarnus erythraeanus, a widespread Red Sea sponge, from the shallow and mesophotic reef, to moderate and acute temperature elevation (2°C and 6°C, respectively) for short and long term periods (two and 35 days, respectively) by measuring physiological parameters (respiration, oxygen removal, pumping rates, and photosynthetic efficiency), and the microbiome composition change. The results indicated that mesophotic and shallow populations of D. erythraeanus are highly tolerant to both moderate and acute heat stress, demonstrating a high survival rate (100%) across the experimental treatments, with no visible signs of bleaching or necrosis. Exposure to heat stress resulted in significant alterations in the physiological parameters of sponges, including higher respiration rate and lower photosynthetic efficiency. These alterations were accompanied by correspondingly significant microbial adjustments, thus emphasizing the essential role of the microbiome in the host’s ability to persist when facing essential environmental stress. Moreover, while shallow and mesophotic sponges showed similar physiological tolerance to heat stress, their microbial response differed: while the microbiome diversity of the mesophotic sponges remained stable throughout the experiment, the shallow one significantly changed. This result suggests that their underlying coping mechanisms might differ between mesophotic and shallow populations. Since the associated-microbiome is largely regulated by the sponge-host genetics, difference in microbial adjustments to stress between populations, could indicate genetic variability between hosts. Therefore, while the results of this study support the hypothesis that mesophotic coral reefs could serve as thermal refugia for some sponge species, it raises the question regarding the validity of MCEs as a refuge for shallow populations. Finally, it emphasizes the crucial need to elucidate the underlying mechanisms governing the sponge-microbiome interactions, specifically in the context of the anticipated climate change scenarios.

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“…MCE community structure is affected by the exponential decrease of light across depth (Kahng et al, 2019) and by the corals' reliance on photoautotrophic carbon production via their endosymbionts (Rädecker et al, 2021). Most coral species at these depths are adapted to certain environmental conditions and can only thrive within a narrow depth range (i.e., "depth-specialists"; Liberman et al, 2022). A few corals, however, are able to thrive across a wider depth range (i.e., "depth-generalists").…”

Section: Introductionmentioning

confidence: 99%

Octocorals in the Gulf of Aqaba exhibit high photosymbiont fidelity

2022

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Symbiotic associations, widespread in terrestrial and marine ecosystems, are of considerable ecological importance. Many tropical coral species are holobionts, formed by the obligate association between a cnidarian host and endosymbiotic dinoflagellates of the family Symbiodiniaceae. The latter are abundant on coral reefs from very shallow water down to the upper mesophotic zone (30–70 m). The research on scleractinians has revealed that the photosymbiont lineages present in the cnidarian host play an important role in the coral’s ability to thrive under different environmental conditions, such as light regime and temperature. However, little is known regarding octocoral photosymbionts, and in particular regarding those found deeper than 30 m. Here, we used ribosomal (ITS2) and chloroplast (23S) markers to uncover, for the first time, the dominant Symbiodiniaceae taxa present in 19 mesophotic octocoral species (30–70 m depth) from the Gulf of Aqaba/Eilat (northern Red Sea). In addition, using high-throughput sequencing of the ITS2 region we characterized both the dominant and the rare Symbiodiniaceae lineages found in several species across depth. The phylogenetic analyses of both markers were in agreement and revealed that most of the studied mesophotic octocorals host the genus Cladocopium. Litophyton spp. and Klyxum utinomii were exceptions, as they harbored Symbiodinium and Durusdinium photosymbionts, respectively. While the dominant algal lineage of each coral species did not vary across depth, the endosymbiont community structure significantly differed between host species, as well as between different depths for some host species. The findings from this study contribute to the growing global-catalogue of Cnidaria-Symbiodiniaceae associations. Unravelling the Symbiodiniaceae composition in octocoral holobionts across environmental gradients, depth in particular, may enable a better understanding of how specialized those associations are, and to what extent coral holobionts are able to modify their photosymbionts.

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Soft coral reproductive phenology along a depth gradient: Can “going deeper” provide a viable refuge?

Cited by 8 publications

References 70 publications

Speciation across depth gradients in reef corals

Speciation across depth gradients in reef corals

A comparison of mesophotic and shallow sponge holobionts resilience to predicted future temperature elevation

Octocorals in the Gulf of Aqaba exhibit high photosymbiont fidelity

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