Historic dispersal barriers determine genetic structure and connectivity in a sandy beach brooder

The supralittoral zones of sandy beaches are particularly vulnerable to coastal development and other activities that cause localised habitat destruction. Supratidal species, such as peracarid crustaceans, which lack a pelagic larval phase tend avoid direct contact with the swash, therefore expected be distributed isolated populations, implications for their long-term survival. Genetic population structure one pill bug Tylos capensis , was investigated based on mitochondrial cytochrome c oxidase subunit I (COI) haplotype sequences, assess demographic history regional connectivity in presence potential dispersal barriers (an estuary, cliffs) along Indian Ocean coast South Africa. Here, bugs demonstrated strong significant genetic at scale, 3 distinct clades across species’ geographic distribution. At spatial cliffs intersecting high shore appeared barrier gene flow between adjacent while permanently open estuary did not limit flow. Estimates historic patterns COI differentiation coincided greater continuity during Pleistocene glaciations sea levels -75 -120 m, when African south probably dominated by beaches. While among low-dispersing populations is unlikely benefit from network closely spaced protected areas, nature this coupled cryptic diversity inherent taxon, emphasizes need protection. importance protecting intact littoral active zone highlighted.