A quantitative and statistical biological comparison of three semi-enclosed seas: the Red Sea, the Persian (Arabian) Gulf, and the Gulf of California

Abstract

Similar habitats separated by great distances can provide remarkable examples of convergent evolution in biological diversity, and have been influential in our understanding of community ecology, historical biogeography, and evolution. Here, we compare three semi-enclosed seas in arid regions of the northern hemisphere, the Red Sea, the Persian (Arabian) Gulf, and the Gulf of California, and test whether they show similar biodiversity patterns. Despite large geographic separations between the seas, the similar shapes and latitudinal locations lead to several analogous abiotic conditions. These similarities, however, do not result in equivalent biodiversity patterns, even when correcting for different regional species pools. Comparisons revealed that the Red Sea contains a greater species diversity of vertebrates, but that the Gulf of California contains the greatest species diversity of invertebrates. Notably, vertebrate abundance patterns were statistically similar between the Persian Gulf and the Gulf of California. Divergences are likely due to variable habitats within each sea, several influential abiotic differences, and dissimilar histories among the seas. While these results support a null hypothesis of biological dissimilarity despite abiotic similarities, they are the first statistical comparisons of the biotas of these three regions. Continued statistical comparisons among marine ecosystems have the potential to reveal ecological and evolutionary patterns that typically go unnoted.