Latitudinal patterns of diversity and abundance in North Atlantic intertidal boulder-fields

In order to study taxon richness, biodiversity and abundance patterns in the North Atlantic from temperate latitudes through Arctic to high Arctic latitudes, we recorded the faunas (at ELWS level) colonizing 20 cobbles from three sites at each of seven boulder-field localities (south-west England, 50 degrees N; Wales, 51 degrees N; west Scotland, 56 degrees N; Iceland, 64 degrees N; Tromso, 70 degrees N; Svalbard, 77 degrees N, 79 degrees N). Inverse correlations were found between latitude and all measures of richness (species, orders, and phyla numbers) and biodiversity (S-W, P). However, these correlations were driven mostly by the consistently impoverished Arctic sites; an even cline of decreasing diversity from south to north did not exist. Multidimensional scaling revealed two communities, temperate-subarctic species-rich and high arctic species-poor. Evenness as measured by Pielou's index was similar across all latitudes. Abundance data exhibited a similar trend to the species richness and diversity data with a significant negative correlation with latitude, but when Arctic data were excluded the correlation vanished.