Abstract

ABSTRACT: The distribution patterns of 6 phytal amphipod species of the genus Hyale that occur on the intertidal rocky shores of Coquirnbo, Chile, are described. The species show habitat segregation with respect to the wave-exposure gradient: H. maroubrae (small species, < 0.6 mm cephalon length) and H. rubra (large species, >0.6 mm cephalon length) occurred in protected environments, whereas H. grandicornis, H hirtipalma and H. m e d ~ a(l arge species) and Hyale sp. (a small species) inhabited exposed environments. With the exception of Hyale sp., all the species were also found in areas with intermediate exposure. However, when they coexist, Hyale spp. show differential occurrence according to microhabitat utilization: in protected environments H rubra was found exclusively on algal patches with high canopies, whereas H. maroubrae was abundant on patches with low canopies. In the exposed sectors, the species were found mainly on algal patches with low canopies; they showed pronounced segregation among patches, with Hyale sp. being restricted to turf-forming filamentous algal patches. The association of amphipod occurrence with canopy height and with occasional and seasonal algal patch occurrence in protected environments suggests that the distribution and coexistence of Hyale spp. are controlled by predation and the proximity to the colonization sectors (subtidal). In contrast, the permanent algal patch occurrence in exposed env~ronmentss uggests that interspecific competition is the main factor influencing the distribution and coexistence patterns of Hyale spp., with low canopy algal patches and water movement playing important roles in maintaining the presence of small species with poor competitive ability.