Genetic variation and population structuring in two brooding coral species (Siderastrea stellata and Siderastrea radians) from Brazil

Abstract

Siderastrea stellata and S. radians are scleractinian coral species that present a remarkable overlap of diagnostic characteristics and sympatric distribution. Moreover, both are viviparous with similar reproductive strategies and with a gregarious larval behavior. Samples of both species from the Brazilian coast were analyzed using 18 isozymic loci to quantify their genetic variability and populational structure. Results confirmed species identity, high intrapopulational variability and revealed moderate genetic structuring among all samples (S. stellata: F (ST) = 0.070; S. radians: F (ST) = 0.092). Based on genotypic diversity analysis, there was evidence that local recruitment may have a minor role in the populations (mean, G ( o ):G ( e )= 1.00 +/- 0.0003 SD for S. stellata and 0.99 +/- 0.0023 SD for S. radians). Deviations towards heterozygote deficiencies found in both Siderastrea species could be explained by the Wahlund effect, since there was evidence that populations might be composed of colonies of different ages. In S. radians it is also likely that there is some inbreeding occurring in the studied populations. Despite the brooding pattern and the gregarious larval behavior, our data suggest the occurrence of gene flow along the Brazilian coast. This is the first study on population genetics of Brazilian reef corals.

Population dynamics of Siderastrea stellata Verrill, 1868 from Rocas Atoll, RN: implications for predicted climate change impacts at the only South Atlantic atoll

“…The taxonomy of this group has been debated and previously S. stellata was considered the only siderastreid in Brazil (Laborel 1974, Maida andFerreira 1997). Recently, the presence of S. radians and S. siderea was confirmed on the Brazilian coast (Neves et al 2008, 2010, Nunes et al 2011 however, neither of those investigations included specimens collected at Rocas Atoll and up to now, only the occurrence of S. stellata is confirmed in this atoll.…”

First record of Flabellina dana Millen and Hamann, 2006 (Mollusca: Nudibranchia) in the South Atlantic Ocean

“…It is the only known western Atlantic Flabellinidae with annulate rhinophores ( Figure 2C) (Millen and Hamann, 2006). Species distribution ranging from the Caribbean Sea as far as the Brazilian coast is not novelty among marine organisms, with examples in cnidarians (Neves et al 2006;Neves et al 2008;Neves et al 2010) and reef fishes Joyeux et al 2001;Rocha et al 2005;Floeter et al 2008;Olavo et al 2011). Concerning nudibranchs, the similarity between the Brazilian and Caribbean fauna has been reported since 1970's (Marcus 1970;Marcus and Marcus 1970;Padula and Santos 2006).…”

Pigmentation changes in Siderastrea spp. during bleaching events in the costal reefs of northeastern Brazil

“…Our results are sufficiently robust to support this argument, as pink colonies of Siderastrea spp. were observed on the coastal reefs of Cabo Branco in the summer of 2005, and then again in 2007-2008. Some colonies identified in the field as S. stellata could be in fact S. radians since, according to Neves et al (2008), both species may exhibit similar patterns of pigmentation changes during bleaching events in Brazilian reefs. We suggest that episodes of pigmentation changes in the Siderastrea of Brazilian reefs have been overlooked for the last 40 years (since Laborel 1970), and need to be examined more deeply.…”

“…All colonies analyzed in this study were reported as Siderastrea spp. in view of the difficulty in distinguishing two species of Siderastrea that occur in the Brazilian reefs (Neves et al, 2008): S. radians (Pallas, 1766) and S. stellata Verril, 1868. We hypothesized that bleaching is a function of environmental variables, and coral pigmentation shows various stages and intensity, that can be identified and monitored.…”