Abstract

It has been proposed that species associated with shallow rocky bottoms in the southern Colombian Caribbean Sea are affected by two biogeographic barriers: the Magdalena River plume (MRP) and the combination of the absence of rocky bottoms and the almost permanent upwelling in the Guajira peninsula (ARB+PUG). We evaluated whether these barriers had generalized genomic effects on the phylogeographic structure of the West Indian top shell (Cittarium pica), a crucial fishery resource in many areas of the Caribbean Sea. Ten species-specific microsatellite loci, 55,112 SNPs from ddRADseq, and COI gene were used on samples of C. pica collected at five Colombian localities (Cabo de la Vela; Santa Marta; Cartagena; Isla Fuerte; and Capurganá). Genetic structure analyses performed for microsatellite and SNP loci indicated that there are three genetic groups of C. pica in Colombia (pop 1: Cabo de la Vela; pop 2: Santa Marta; pop 3: Cartagena+Isla Fuerte+Capurganá). However, both SNPs and COI gene were congruent in showing a phylogeographic break caused by only the ARB + PUG (AMOVA: ΦCT-SNP=0.224, p < 0.05; ΦCT-COI=0.722, p < 0.05), which was confirmed by the maximum-likelihood and network trees. In contrast, MRP was shown to be a permeable barrier to gene flow. Demographic history analysis indicated that C. pica experienced historical changes in population size during the last glaciation period. Cittarium pica is a biological model to demonstrate how the ARB + PUG barrier could affect marine organisms living in shallow rocky habitats, mainly those lacking larvae or having a short-lived larval phase in the southern Caribbean Sea. Finally, some recommendations for fisheries management and conservation C. pica populations are discussed.