Abstract
Microsatellite markers are invaluable tools for assessing genetic diversity and elucidating population structure across any species. This study reports the development and application of ten novel polymorphic microsatellite loci for Tectarius striatus, a littorinid species native to the shores of Macaronesia, a geographical region that includes the archipelagos of the Azores, Madeira, Selvagens, Canary Islands, and Cabo Verde. These markers together with a portion of the COI gene were used to genotype 65 individuals, using Illumina amplicon -sequencing across five geographically distinct populations. Our analysis shows moderate to high levels of allelic diversity across all populations. Furthermore, microsatellite markers supported genetic structure between a distant population of Cabo Verde Archipelago and the northern Macaronesian archipelagos. Conversely variation of the COI showed high levels of homogeneity across the sampled populations. While the presence of null alleles and moderate levels of missing data at several loci represent challenges to this study, the overall consistency of our results with earlier research underscores the reliability of microsatellite markers for population genetic inference in this marine gastropod. Nevertheless, our findings highlight the need for cautious interpretation of diversity estimates and population structure metrics, particularly when null alleles are frequent, and underscore the value of expanding the panel of available microsatellite markers for Tectarius striatus and related taxa to improve resolution and accuracy for future studies.