Vertical stratification of mobile epiphytal arthropod assemblages between the canopy and understorey of subtidal macroalgae

• Published in: Marine biology Vol. 150; no. 3; pp. 427 - 441
• Main Author: Hirst, Alastair J
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer-Verlag 01.01.2007; Berlin Springer; Springer Nature B.V
• Subjects: Algae; analysis of variance; analytical methods; Animal and plant ecology; Animal, plant and microbial ecology; Aquatic ecosystems; Arthropods; Biological and medical sciences; biomass; canopy; fauna; Fundamental and applied biological sciences. Psychology; Habitats; herbivores; macroalgae; Marine; Marine biology; Multivariate analysis; Sea water ecosystems; Statistical analysis; Stratification; Synecology; understory; Variance analysis; Vertical; Algae; Arthropoda; Invertebrata; Stratification; Community; Thallophyta; Canopy(vegetation)
• ISSN: 0025-3162; 1432-1793
• DOI: 10.1007/s00227-006-0345-x

This study examined patterns of faunal stratification between vertical strata by partitioning subtidal macroalgal communities into vertically contiguous (and hence paired) canopy and understorey habitats. Such floristic strata are often clearly defined in temperate subtidal communities and have been the focus of a range of other, primarily botanical, studies. Previous studies that have touched upon this subject have used statistical tests that require spatially independent samples, yet have collected samples that are often spatially contiguous and therefore not statistically independent. Here an analytical approach for examining faunal stratification in subtidal macroalgal assemblages using split-plot ANOVA for univariate data and a novel multivariate test suitable for analysing assemblage-level paired-sampled data is proposed. Differences in faunal assemblage structure between habitats were primarily attributed to the distribution of two functional feeding groups: filter-feeding and scavenging arthropods. Filter-feeders were more abundant amongst the canopy, whereas scavengers were more abundant in the understorey. No pattern was detected for herbivorous arthropods. These patterns are consistent with the feeding ecology of these functional groups and reflect expected differences in the relative availability of trophic resources between habitats, commensurate with the physical structure of the environments. Contrary to expectation, understorey algal habitats supported faunal assemblages that were as diverse, or more diverse than the canopy habitats, despite comprising smaller habitable spaces (in terms of algal biomass) and generally supporting fewer faunal individuals. Trophic stratification of epifaunal assemblages is suggested as a mechanism whereby faunal diversity is enhanced in these environments.