RESEARCH PAPER Aggregate patterns of macrofaunal diversity: An interocean comparison Omar Defeo 1 | Carlos A. M. Barboza 2 | Francisco R. Barboza 1 | William H. Aeberhard 3 | Tatiana M. B. Cabrini 4 | Ricardo S. Cardoso 4 | Leonardo Ortega 5 | Viviane Skinner 4 | Boris Worm 6 1 Unidad de Ciencias del Mar, Facultad de Ciencias, Igu a 4225, Montevideo 11400, Uruguay 2 N ucleo em Ecologia e Desenvolvimento S ocio-Ambiental de Maca e, Universidade Federal do Rio de Janeiro. Av. S~ ao Jos e do Barreto, 764 - S~ ao Jos e do Barreto, Maca e, RJ 27965-045, Brazil 3 Department of Mathematics and Statistics, Dalhousie University, Halifax, NS B3H4R2, Canada 4 Laborat orio de Ecologia Marinha, Depto. de Ecologia e Recursos Marinhos, Universidade Federal do Estado do Rio de Janeiro, Av. Pasteur, 458, Rio de Janeiro, RJ 22290-240, Brazil 5 Laboratorio de Oceanografía, DINARA, Constituyente 1497, Montevideo 11200, Uruguay 6 Department of Biology, Dalhousie University, Halifax, NS B3H4R2, Canada Correspondence Omar Defeo, Unidad de Ciencias del Mar, Facultad de Ciencias, Igu a 4225, 11400 Montevideo, Uruguay. Email: odefeo@dinara.gub.uy Editor: Sally Keith Funding information Programa Pesquisador Visitante Especial, Grant Number: 88881.030807/2013-01; CSIC-Grupos Uruguay Abstract Aim: While geographical patterns of species richness are reasonably well explored for single well- studied taxa, less is known about aggregate patterns of total richness for major biomes and their environmental correlates. Here we analyse continental-scale aggregate patterns of macrofaunal diversity for sandy beaches, a dominant habitat along the Atlantic and Pacific coasts of South America. Location: South American coastlines. Time period: Present day (data amassed from studies performed since 1971). Major taxa studied: Benthic macrofauna, including crustaceans, polychaetes and molluscs. Methods: We compiled richness information for all macrofaunal groups on 263 sandy beaches in South America using standard criteria. We further matched these data with environmental varia- bles including sea surface temperature (SST), chlorophyll a, grain size, beach slope, tide range and various morphometrics. We used generalized linear mixed models to relate environmental factors to observed variation in total macrofaunal richness across all beaches, testing competing hypothe- ses about environmental correlates and possible drivers of latitudinal diversity. Results: Macrofaunal richness decreased from tropical to temperate beaches in the Pacific and fol- lowed a parabolic trend in the Atlantic, with the highest biodiversity found at tropical and mid- latitudinal bands. Beach slope, tidal range and chlorophyll a mostly explained latitudinal trends in macrofaunal richness, followed by grain size, SST and ocean basin. Main conclusions: This study indicates that richness of macrofaunal species at a given beach is most closely related to characteristics of the physical habitat, such as beach slope, area and grain size. At this scale, planktonic food supply also appeared to be more important than temperature, which is a dominant explanatory variable of global-scale variation in species richness. KEYWORDS benthic macrofauna, environmental correlates, latitudinal diversity, macroecology, sandy beaches, South America 1 | INTRODUCTION Striking non-random latitudinal patterns in diversity on land and in the ocean have been a major research topic in ecology and biogeography (Hillebrand, 2004; Gaston, 2000; Rohde, 1992). While monotonic increases in species richness are observed for vertebrates and plants on land (Belmaker & Jetz, 2011; Kreft & Jetz, 2007), marine species groups can show more varied patterns, including subtropical or temper- ate peaks in diversity (Tittensor et al., 2010; Woolley et al., 2016). Yet the majority of studies have focused on single taxa, while aggregate Global Ecol Biogeogr. 2017;26:823–834. wileyonlinelibrary.com/journal/geb V C 2017 John Wiley & Sons Ltd | 823 Received: 27 September 2016 | Revised: 29 November 2016 | Accepted: 2 December 2016 DOI: 10.1111/geb.12588