The Cones of Oman: Endemism and Divergence in a Remarkable Marine Setting

The enormous diversity of Conidae in the Indo-West Pacific (IWP) makes the group an attractive model for testing tropical marine diversification, but its incredible richness makes species delineation challenging. Throughout his career, Alan Kohn championed an integrative taxonomic approach and a deep study of variation to delimit cone-snail species to understand this radiation. Most recently, sequence data has provided objective measures of genetic connectivity of populations and is helping to test species limits in light of distributions and ecologies. To expand and better frame our understanding of cone diversity, we provide a broad overview of the cones of Oman, a previously genetically poorly sampled area of the world ocean with unusual and heterogeneous oceanography, where corals and kelp mix, and seasonal upwelling and oxygen minimum zones influence ecosystems. We provide mitochondrial sequence data for 30 of the 54 nominal species recorded from Oman based on new collections and analyze genetic differentiation across the IWP based on available comparative sequence data. We found that endemism is remarkable, with 37–41% of genetically characterized species and 53–56% of all species unique to Oman, Arabia, or the Arabian Sea. Several wide-ranging cone species are geographic mosaics, composed of divergent, allopatric populations, fitting Mayr's concept of polytypic species. Genetic data show other putative endemic species to be genetically connected to species outside the region, suggesting that they are variants, rather than species. These include Conus nigropunctatus G. B. Sowerby II, 1858 (= C. catus Hwass, 1792), C. sumatrensis Hwass, 1792 (= C. vexillum Gmelin, 1791), and C. thomasi G. B. Sowerby III, 1881 (= C. terebra Born, 1778). Life history is an important determinant of endemism. Nearly all (94%) of the broadly distributed IWP species have multispiral protoconchs suggestive of longer planktonic development and exchange potential, whereas two-thirds of regional endemics do not, indicating more restricted geographic exchange.