Species Boundaries ofAstreoporaCorals (Scleractinia, Acroporidae) Inferred by Mitochondrial and Nuclear Molecular Markers

Abstract

The genus Astreopora is a small but ancestral group in Acroporidae, which is one of the most diverse and dominant families of scleractinian coral in Indo-Pacific reefs. We estimated the species boundaries of Astreopora corals using two molecular markers: a mitochondrial non-coding region and a nuclear ribosomal 5.8S region. Seven species (59 specimens) commonly observed around Japan (Astreopora expansa, A. gracilis, A. incrustans, A. listeri, A. myriophthalma, A. cf. suggesta, and Astreopora sp.1) were investigated, and we observed no genetic divergence in the mitochondrial marker, suggesting that these species are closely related, consistent with a species complex or recent divergence, although genotyping by the marker is not so sensitive. In the nuclear 5.8S region, 121 clones consisted of six species were divided into the four major genetic groups. Although there were no monophyletic clades, the two dominant species A. myriophthalma and A. gracilis rarely shared the same haplotypes, suggesting that gene flow is limited between them. However, A. incrustans frequently shared the same haplotypes with A. gracilis although the distributions do not overlap. We found that the ancestral genus Astreopora in Acroporidae shows less genetic variation than traditionally identified morphospecies. Although further research on fertilization rate among these species is required to determine if there are reproductive barriers, the low level of genetic diversification in this genus hints that some ecological differences among acroporid corals play a role in the evolution of scleractinian corals, considering that the other members of this family, Acropora and Montipora, are highly diversified.

The New Systematics of Scleractinia: Integrating Molecular and Morphological Evidence

“…Larger geographic contrasts such as between Red Sea and Pacific Ocean populations of Dipsastraea and Stylophora have also revealed molecular separation between regions Arrigoni et al 2012;Keshavmurthy et al 2013). However, to reach a stage where taxonomic revisions can be attempted, broad geographic sampling across the Indo-Pacific and detailed studies of closely-related species are necessary, such as in the case of species in Astreopora (Suzuki and Nomura 2013), Pocillopora (Pinzón and LaJeunesse 2010;Pinzón et al 2012Pinzón et al , 2013Torda et al 2013a, b;Marti-Puig et al 2014;Schmidt-Roach et al 2013, 2014 and Psammocora (Benzoni et al 2010;Stefani et al 2008a). In particular, boundaries among Psammocora species were clarified through a series of rigorous molecular and morphological analyses (Stefani et al 2008a, b;Benzoni et al 2007Benzoni et al , 2010, which saw 24 nominal species reorganised as seven valid species-P. albopicta, P.…”

A Likely Ancient Genome Duplication in the Speciose Reef-Building Coral Genus, Acropora

“…The Acroporidae is a family of reef-building corals within the phylum Cnidaria, one of the basal phyla of the animal clade (Richards et al., 2013, Wallace, 2012, Wallace and Rosen, 2006). Astreopora (Anthozoa: Acroporidae) is the sister genus in the acroporid lineage according to fossil records and molecular phylogenetic evidence (Fukami et al., 2000, Suzuki and Nomura, 2013, Wallace, 2012). Importantly, Acropora (Anthozoa: Acroporidae), one of the most diverse genera of reef-building corals, including more than 150 species in the Indo-Pacific Ocean, is thought to have originated from Astreopora ∼60 mya with several species turnovers (Edinger and Risk, 1994, Renema et al., 2008, Wallace, 2012, Wallace and Rosen, 2006).…”

A framework for in situ molecular characterization of coral holobionts using nanopore sequencing

“…However, due to slow nucleotide substitution rates for mitochondrial genes within anthozoans 9 , common genetic markers such as the cytochrome c oxidase subunit I or the cytochrome b are not discriminant enough to identify corals at the species level 10,11 . Nuclear markers like the 18S or the 5.8S rRNA 12,13 are generally more variable between species although multi-locus and microsatellite analysis are often required to precisely determine species boundaries 14 .…”