The reef-building coral genus Acropora is essential for coral
reefs due to its role in the reef, as a habitat for other marine
organisms. The diversity of coral species might have arisen explosively,
accompanied by hybridization in response to historical climate change,
Pleistocene, with sea level changes. Here, we aimed from integrative
approaches (morphology, genetics, and reproduction) to evaluate the
speciation history of the four tabular Acropora species
(Acropora aff hyacinthus, A. cf bifurcata,
A. cf cytherea, and A. cf subulata). Here,
we show that introgression might have a minor role in specifying the
four tabular Acropora spp. Instead, rapid genetic divergence
occurred, accompanied by morphological differences and gamete
incompatibility. Furthermore, extensive morphological analyses showed
that these four species were distinguishable from morphology, and their
gamete incompatibility was sufficiently high to prevent hybridization.
Population structure and principal component analyses with the SNPs
(>60,000) indicated these four species were also
distinctive, and the ABBA-BABA test did not support introgression among
these species. In addition, many coding and noncoding RNA sequences were
in the high genetic variances among four species with high Fst loci
along the genome. Comparing these orthologs among other Acropora
species suggests that many of these genes were under positive selection,
which could be associated with their divergence at spawning time, gamete
incompatibility, and morphological differences. These results show that
the speciation of the tabular Acropora occurred without
hybridization, and divergence accompanying the genes’ rapid evolution
could be associated with specifying in the species-rich Acropora.