Looking at taxa that could dominate Anthropocene reefs, the fire corals, Millepora spp., represent compelling alternative because of their similar role than scleractinian corals. However, species identification has been the subject of much debate over the past 150 years. As they may turn as among the last refuges for reef biodiversity, it is critical to accurately delimit their species boundaries to appreciate better their resilience to future environmental conditions. Combining morphological and molecular approaches, we investigated Millepora species delimitation in Réunion Island where three species co-occur: Millepora exaesa, Millepora platyphylla and Millepora tenera. Our results showed that both pore characters and polyp morphologies successfully distinguished species. Gastropore and dactylopore numbers and diameters should be used as standard traits in Millepora. Regarding molecular delineation, the mitochondrial gene clearly segregated the species, whereas the nuclear gene showed shared haplotypes between species, likely influenced by ancestral polymorphism. Confirming the results of a recent study on Red Sea fire corals showing their distinction from the Indo-Pacific ones, we emphasize that formal re-descriptions of the Indo-Pacific M. cf. platyphylla and M. cf. exaesa are needed. Our study highlights the importance of a trait-based qualitative and quantitative approach coupled to molecular delineation, especially for structurally important reef species.
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EB was supported by a Marie Curie fellowship MC-CIG-618480 to study the biogeography of Indo-Pacific fire corals. This study was supported by the program BIOTAS from the French Government (National Agency for Research, ANR-06-BDIV-002). We want to thank the center of studies of marine turtles from Réunion Island (Kelonia) where the study of living polyps could be kindly carried out in aquariums. We are grateful to Xavier Pochon and Ruth Gates who allowed the sequencing of some specimens during the stay of JKL at the Hawaii Institute of Marine Biology. VD benefits from a grant from the Ministry of Science and Technology (Taiwan, no. 107-2611-M-002-011).
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GenBank accession numbers (MK990235-MK990274 and MK972718-MK972749).
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Electronic supplementary material
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Supplementary material 1 Sampling details and GenBank accession numbers for the 16S mitochondrial gene and the ITS nuclear gene. All samples were collected on the same site, “Kiosque” at Saint Leu, Réunion Island. (DOCX 16 kb)
Supplementary material 2 Maximum Likelihood phylogenetic reconstruction based on the ITS2 gene of Millepora specimens from Réunion Island together with specimens of M. cf. dichotoma, M. intricata, M. tenera, M. cf. platyphylla and M. cf. exaesa from Okinawa (Takama et al. 2018). Numbers near the nodes are bootstrap supports (PDF 50 kb)
Supplementary material 3 Pore measurements of the 27 Millepora colonies analyzed: 3 M. cf. exaesa (colony E2 to E4), 6 M. cf. platyphylla (colony P22 to 26 and P30) and 18 M. tenera at 4 pore traits of datatype 1: GD = gastropore diameter, ND/C = number of dactylopores per cyclosystem, DD = dactylopore diameter and dis = mean distance between a gastropore and each dactylopore around it (DOCX 28 kb)
Supplementary material 4 Pore measurements of the 27 Millepora colonies analyzed: 3 M. cf. exaesa (colony E2 to E4), 6 M. cf. platyphylla (colony P22 to 26 and P30) and 18 M. tenera at 9 pore traits of datatype 2 with 5 replicates per colony: NG = number of gastropores, NDC = number of dactylopores included in a cyclosystem, NFD = number of free dactylopores, NTD = number of total dactylopores (= NDC + NFD), LNDC = least number of dactylopores per cyclosystem, MNDC = maximum number of dactylopores per cyclosystem, NSeC = number of separate cyclosystems, NShC = number of shared cyclosystems, NOC = number of open cyclosystems (DOCX 26 kb)
Supplementary material 5 Photos of polyps: dactylozoids and gastrozoids of the three species of Millepora from Réunion Island. a) M. cf. exaesa, b) M. tenera, c) M. cf. platyphylla (DOCX 878 kb)
Supplementary material 6 Distribution of intra and inter-specific genetic distances showing a barcoding gap. Plot produced on the web server ABGC (Puillandre et al. 2012) using the Kimura-2-Parameters genetic distance. (PDF 14 kb)
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Boissin, E., Leung, J.K.L., Denis, V. et al. Morpho-molecular delineation of structurally important reef species, the fire corals, Millepora spp., at Réunion Island, Southwestern Indian Ocean. Hydrobiologia 847, 1237–1255 (2020). https://doi.org/10.1007/s10750-020-04179-0
- Morphological identification
- DNA barcoding
- Species delimitation methods
- Integrative taxonomy
- Trait-based quantitative approach