High-latitude connectivity of the scleractinian coral Acropora tenuis in the south-western Indian Ocean, identified using nuclear intron and mitochondrial sequence data

All scleractinian corals in southern Africa occupy the high-latitude margins of their biogeographical range, with some straddling multiple biogeographical regions. Connectivity among these populations is essential to maintain genetic diversity, and thus their conservation value. Therefore, the aim of this study was to elucidate the genetic diversity, connectivity and structure of Acropora sp. populations. Acropora sp. were sampled at four intertidal and subtidal sites over a distance of ~320 km, and assessed using primers that amplify the 3/550 nuclear intron found within the carbonic anhydrase gene and the mitochondrially encoded cytochrome oxidase I region of DNA. Results resolved the presence of four putative Acropora clades, genetically disparate according to 3/550 nuclear intron data. In contrast to this, cytochrome oxidase I data confirmed the presence of a single species: A. tenuis. Cytochrome oxidase I data were highly conserved at species level, supporting previous notions that this gene may not be suitable for species level delineation in acroporids. Genetic structuring and diversity of A. tenuis  among the four sites revealed similar characteristics to Acropora austera of northern KwaZulu-Natal and Mozambique. Little genetic differentiation was found between all possible regions, suggesting no significant genetic differentiation across the biogeographical regions tested. A higher degree of isolation and lower differentiation and moderate to high connectivity indices suggested periods of lower-latitude colonisation and periods of population attrition may be a feature in the ecology of this species.Keywords: genetic connectivity, hybridisation, phylogeographyAfrican Journal of Marine Science 2013, 35(2): 233–24

Mitochondrial DNA is unsuitable to test for isolation by distance

CITATION: Teske, P. R., et al. 2018. Mitochondrial DNA is unsuitable to test for isolation by distance. Scientific Reports, 8:8448, doi:10.1038/s41598-018-25138-9.The original publication is available at https://www.nature.comTests for isolation by distance (IBD) are the most commonly used method of assessing spatial genetic structure. Many studies have exclusively used mitochondrial DNA (mtDNA) sequences to test for IBD, but this marker is often in conflict with multilocus markers. Here, we report a review of the literature on IBD, with the aims of determining (a) whether significant IBD is primarily a result of lumping spatially discrete populations, and (b) whether microsatellite datasets are more likely to detect IBD when mtDNA does not. We also provide empirical data from four species in which mtDNA failed to detect IBD by comparing these with microsatellite and SNP data. Our results confirm that IBD is mostly found when distinct regional populations are pooled, and this trend disappears when each is analysed separately. Discrepancies between markers were found in almost half of the studies reviewed, and microsatellites were more likely to detect IBD when mtDNA did not. Our empirical data rejected the lack of IBD in the four species studied, and support for IBD was particularly strong for the SNP data. We conclude that mtDNA sequence data are often not suitable to test for IBD, and can be misleading about species’ true dispersal potential. The observed failure of mtDNA to reliably detect IBD, in addition to being a single-locus marker, is likely a result of a selection-driven reduction in genetic diversity obscuring spatial genetic differentiation.https://www.nature.com/articles/s41598-018-25138-9/Publisher's versio