SPECIES DIVERSITY IN SUBTIDAL LANDSCAPES: MAINTENANCE BY PHYSICAL PROCESSES AND LARVAL RECRUITMENT

Abstract

Heterogeneous patterns of species diversity are rarely linked to the processes that maintain them on spatial scales larger than tens of meters. In this study, subtidal landscapes of a New Zealand fjord were used to study the spatial patterns of epifaunal invertebrate species diversity and to test hypotheses about the mechanisms maintaining the patterns. Patterns of species diversity were quantified along 1000-m2 sections of vertical rock wall habitat at three sites separated by 3–6 km of horizontal distance during April–August 1993. Species diversity data from random 0.25-m2 quadrats at four depth strata (3, 5, 10, and 18 m) within a 20 × 50 m area were contoured to reveal spatial patterns at each site. General patterns consisted of localized patches of 300–660 m2 of high diversity (i.e., H′ [Shannon-Weiner diversity index] of 2.0–3.2/0.25 m2 and S [species richness] of 28–32 species/0.25 m2) centered at 10 m depth. High-diversity patches, dominated by bryozoans, sponges, and ascidians, were bounded verti...