The shrubland systems of the Socotra Islands and Madagascar are unique with a large diversity of species for relatively small areas. Four vegetation zones are recognized for the Socotra Island shrublands: arid coastal plain (0-200 m [0-656 ft]), transition zone (200-400 m [656-1312 ft]), arid limestone zone (400-1000 m [1312-3281 ft]), and semi-arid upper zone (Haghier Mountains, 1000-1500 m [3281-4921 ft]). Seven native shrub complexes exist on Socotra Island and include such plant genus as croton (Croton), nettle spurge (Jatropha) and desert rose (Adenium). Madagascar shrublands are dominated by species of Euphorbia shrubs and receive less than 600 mm (24 in) in the interior section of the bioregion, and less than 400 mm (16 in) along the coast. The Vezo fishing people live along the coast, while the interior edge is inhabited by the Mikea hunter-gatherer groups.