Aim: Herbivorous reef fishes are considered to have difficulty digesting plant material at extratropical temperatures, and are thus largely restricted to tropical waters where they are thought to have evolved. However, the herbivorous Kyphosidae, with both temperate and tropical species, provides an ideal opportunity to test this view. Previous studies have resolved the taxonomy and distribution patterns of all species. Here, we use a calibrated phylogeny to analyse the age, geographical origin and pattern of diversification of kyphosids to determine their origins in space and time, and thus refine hypotheses on the evolutionary origins of herbivory in reef fishes. Location: Pacific Ocean, Atlantic Ocean, Indian Ocean, Western Australia. Methods: The age and geographic origin of Kyphosidae were determined by incorporating fossil calibrations and species distributions onto a phylogeny of all extant species based on fragments from mitochondrial markers and three nuclear markers, and using Bayesian modelling to reconstruct ancestral distributions. Evolution of both diet and tooth shape were also examined using Bayesian ancestral reconstruction. Results: Ancestral reconstruction suggested a subtropical, southern hemisphere Indo-Pacific origin for the family. The chronogram indicates that Kyphosus originated in the early Miocene, and that tropical diversity reflects very recent diversification. Main conclusions: Contrary to the general perception that herbivorous reef fishes invaded high latitudes from the tropics, herbivorous kyphosids evolved at intermediate latitudes in the southern hemisphere and subsequently diversified into low latitudes where several species dispersed recently to achieve circumglobal distributions. The southern temperate/subtropical reef environment appears to have generated episodes of diversification in several, well-established, widespread reef fish taxa. Some of these reef fish taxa have remained restricted to southern temperate reef environments despite a long tenure in the Cenozoic (e.g. odacines and aplodactylids), and some such as the kyphosids which diversified very recently in both hemispheres resulting in both regional endemics and species with worldwide distributions.

High_latitude_origin_of_sea_chubs_Knudsen_etal_2019_J_BiogeogrThe tar.gz file holds multiple directories with bash codes for unix and R-codes for analysis of time calibrated phylogenetic trees and xml-files to be used with BEAST v1.8.4. The tar.gz file can be uncompressed in a unix terminal, and can also be git cloned from this bitbucket repository: https://xanthic_Rudderfish@bitbucket.org/xanthic_Rudderfish/high_latitude_origin_of_sea_chubs_suppl_info_knudsen_etal_2019.git . The README file has instructions and guides on how the different files and directories can be used to rerun the analysis and reproduce the phylogenetic trees presented in the publication. The supporting information associated with this publication also holds information and instructions to how the analysis were done.High_latitude_origin_of_sea_chubs_Knudsen_etal_2019.tar.gz