Evidence of species-specific habitat selectivity of Acropora corals based on identification of new recruits by two molecular markers

One of the most abundant genera of scleractinian corals, Acropora, shows considerable zonation along reef slopes. The zones are thought to be established by both selective larval settlement and post-settlement selection. The latter has been credited as more important, possibly due to the obvious relationship between colony shapes and habitat-specific environmental stress. However, there is no evidence that the former has less influence on the creation of the zones. To test the hypothesis that larvae settle selectively on species-specific suitable habitat, we identified recruits using mitochondrial and nuclear molecular markers. A 2-step molecular sorting process successfully identified the 7 most dominant species in the area. Comparing the species composition of 3 different depths, the distribution of the settlement of the 3 dominant species A. digitifera, A. hyacinthus and A. tenuis was significantly related to adult zonation, suggesting that Acropora larvae selectively settle on the suitable habitat. This is the first in situ evidence showing selective settlement of coral larvae, and from it we can conclude that the initial stage of the life cycle plays an important role in establishing habitat segregation at the species level in Acropora.