Low genetic diversity and homogeneity in Diadema africanum across distant islands with different population densities
Diadema africanum is an important macro-herbivore that inhabits the subtropical and tropical rocky reefs of the western African coast and the archipelagos of Macaronesia. This species is investigated due to its impact on coastal rocky substrates through its considerably high density. Although much is known about the ecological role of Diadema species, studies on population genetics have not been yet performed. To explore the genetic diversity levels, phylogeographic patterns and demographic features of D. africanum, we analysed sea urchins of 14 localities across the Canary Islands and Cabo Verde archipelagos using mitochondrial marker. This study allowed us to explore the genetic connectivity across, close and within distant areas inside each archipelago. Our results indicated low levels of genetic, haplotype and nucleotide diversity of this species compared to other common sea urchins in the areas. Most populations from the two regions did not show structural genetic differences. Within the Canarian archipelago, two populations obtained a rather low number of different haplotypes and low population density, and a general genetic homogeneity was found across the studied areas. Through our finds of a recent speciation followed by population demographic expansion, we discuss the occurrence of a potential founder effect of D. africanum along the subtropical eastern Atlantic, which explains the obtained genetic features.