Austral Ecology (2021) 46, 965–981 Functional beta diversity of New Zealand fishes: Characterising morphological turnover along depth and latitude gradients, with derivation of functional bioregions ELISABETH M. V. MYERS,*1 DAVID EME,1,2 LIBBY LIGGINS,3,4 EUAN S. HARVEY,6 CLIVE D. ROBERTS5 AND MARTI J. ANDERSON1 1New Zealand Institute for Advanced Study (NZIAS), Massey University, Albany Campus, Auckland, 0745, New Zealand (Email:
[email protected]); 2Unite´ Ecologie et Modeles` pour l’Halieutique, IFREMER, Nantes, France; 3School of Natural and Computational Sciences (SNCS), Massey University, Auckland, New Zealand; 4Auckland Museum, Tamaki¯ Paenga Hira, Auckland, New Zealand; 5Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand; and 6School of Molecular and Life Sciences, Curtin University, Bentley, Western Australia, Australia Abstract Changes in the functional structures of communities are rarely examined along multiple large-scale environmental gradients. Here, we describe patterns in functional beta diversity for New Zealand marine fishes versus depth and latitude, including broad-scale delineation of functional bioregions. We derived eight functional traits related to food acquisition and locomotion and calculated complementary indices of functional beta diver- sity for 144 species of marine ray-finned fishes occurring along large-scale depth (50–1200 m) and latitudinal gradients (29°–51°S) in the New Zealand Exclusive Economic Zone. We focused on a suite of morphological traits calculated directly from in situ Baited Remote Underwater Stereo-Video (stereo-BRUV) footage and museum specimens. We found that functional changes were primarily structured by depth followed by latitude, and that latitudinal functional turnover decreased with increasing depth. Functional turnover among cells increased with increasing depth distance, but this relationship plateaued for greater depth distances (>750 m).