Unusual but consistent latitudinal patterns in macroalgal habitats and their invertebrate communities across two countries

Hannah B Lloyd,Tim M Glasby,Paul E Gribben,Juan J Cruz‐Motta,Pat A Hutchings,Amanda Taylor

doi:10.1111/ddi.13070

Abstract

AbstractAimThe physical characteristics of biogenic habitats and environmental conditions are important determinants of biodiversity, yet their relative importance can change across spatial scales. We aimed to understand how relationships between the physical characteristics of macroalgal habitats and their invertebrate communities varied across spatial scales and whether general ecological patterns occurred across two countries.LocationEighteen sites across the temperate east coasts of Australia (over 1,300 km) and New Zealand (over 1,000 km), with the latitudinal gradient in the two countries overlapping by 6.73 decimal degrees.Time periodJanuary to early April 2012.Major taxa studiedThree intertidal macroalgal habitats in each country and the invertebrate communities within them.MethodsWe measured variation in patch‐ and individual‐level characteristics of macroalgal habitats and their invertebrate communities. Patterns in macroalgal characteristics and communities were compared across latitude, and at smaller spatial scales, and correlated with 26 abiotic environmental variables using multiple multivariate analyses.ResultsSeparately, macroalgal habitat characteristics and communities showed unusual but consistent nonlinear latitudinal patterns, with greater similarity among sites at the edges of the sampled distribution (i.e., north and south) than at centrally located sites. Macroalgal characteristics did not correlate with a particular set of environmental variables; however, communities were structured by sea surface temperature at the country scale and by macroalgal habitat type and biomass within countries. Anthropogenic variables were also important and may have contributed to the unusual nonlinear patterns observed between macroalgal characteristics and communities across latitude.Main conclusionsOur results support other studies showing that large‐scale patterns can emerge from systems where there is high local‐scale variability. The results show that communities within macroalgal habitats respond to both the physical characteristics of the habitat and external environmental conditions (e.g., temperature), suggesting that local‐scale environmental factors, including anthropogenic stressors, may modulate environmental gradients over larger scales.

Highlights

In an era of unprecedented biodiversity loss, there is an increasing need to understand how ecological processes operating at multiple spatial scales influence biodiversity to inform global conservation actions (Gaston, 2000; Loreau, 2001)
We investigated the role of environmental factors in shaping the physical characteristics of macroalgae and the invertebrate communities inhabiting them at continental scales
We found little support for our hypotheses that the physical characteristics of macroalgae and communities would follow latitudinal gradients

Summary

| INTRODUCTION

In an era of unprecedented biodiversity loss, there is an increasing need to understand how ecological processes operating at multiple spatial scales influence biodiversity to inform global conservation actions (Gaston, 2000; Loreau, 2001) Biogenic habitats such as trees, corals and seaweeds are foundation species (sensu Dayton, 1972) that have a range of important ecological roles (Angelini, Altieri, Silliman, & Bertness, 2011; Bellwood, 2001; Ellison et al, 2005; Harley et al, 2012), most obviously they create physical habitat for other species (hereafter “communities”). We used multivariate analyses of invertebrate community structure and composition across a broad range of taxa, but with a lower taxonomic resolution as this approach can be effective at detecting large-scale diversity patterns even when there is high local-scale variability (Anderson, Connell, et al, 2005)

| METHODS

Findings

| DISCUSSION