DOI: 10.5061/dryad.352th
title: Data from: Evolution of codfishes (Teleostei: Gadinae) in geographical and ecological space: evidence that physiological limits drove diversification of subarctic fishes

description: Aim: To develop a holistic biogeographical history of codfishes in the
 subfamily Gadinae based on historical relationships, ecological niche, and
 evolution of physiological tolerances. Two alternative diversification
 scenarios were tested in two co-distributed, Northern Hemisphere clades:
 (1) clade ancestors were temperate, and environmental niche has been
 conserved over evolutionary time, implying that speciation was driven by
 vicariance associated with ice sheet formation; and (2) clade ancestors
 were Arctic, and species convergently adapted to temperate environmental
 conditions, implying that speciation was driven by repeated adaption to
 temperate environments. Location: Northern Hemisphere Arctic and subarctic
 oceans. Methods: Fifty-five new sequences of four genes from 23 tissue
 samples were combined with 10 GenBank sequences to generate a
 time-calibrated phylogenetic hypothesis. Combining the phylogeny with
 information on species' ecological niche tolerances inferred from
 correlational models, I reconstructed ancestral environmental tolerances
 of each of the focal clades. These results were combined with Bayesian
 area-based biogeographical analysis and regional palaeoclimatic history to
 develop a holistic biogeographical history of Gadinae. Results: Of 18
 environmental variables describing species' tolerances to salinity,
 temperature, sea ice concentration, and mixed layer depth, only mean,
 maximum and minimum sea bottom temperature, and mean and minimum sea
 surface temperature showed phylogenetic signal across Gadinae. Both
 ecological niche and geographical distributions of gadine fishes are
 largely conservative, but two clades contain both Pacific and Atlantic
 species. Focal clade divergence time estimates suggest a Pliocene origin
 for both, with further Pleistocene divergence. Main conclusions:
 Reconstructed ancestral environmental tolerances of crown cods and tomcods
 support a temperate origin of both groups. The timing of diversification
 of these two clades and the intolerance of temperate species to sea ice
 suggest that cyclical Arctic ice formation drove divergence. Future sea
 ice reduction may have dramatic consequences for distributions and
 persistence of commercially important species when currently allopatric
 temperate species come into secondary contact.
description: Niche Reconstruction
 & Hypothesis TestingR script for niche
 reconstruction and hypothesis testing. Written for R version 3.1.0 Patched
 (2014-04-10 r65396) -- "Spring Dance" on
 x86_64-apple-darwin10.8.0 (64-bit) platform.NicheReconstruction&HypothesisTesting.RProject DirectoryData to perform analysis in script NicheReconstruction&HypothesisTesting.R. Includes phylogenetic tree, environmental projection data for Northern Hemisphere oceans, median suitability from ecological niche models, and median ecological niche model projection results. Refer to manuscript for additional information on data sources and processing.ProjectDirectory.zip