title: Parallel ecological diversification in Antarctic notothenioid fishes as evidence for adaptive radiation.
abstract: Antarctic notothenioid fishes represent a rare example of a marine species flock. They evolved special adaptations to the extreme environment of the Southern Ocean including antifreeze glycoproteins. Although lacking a swim bladder, notothenioids have diversified from their benthic ancestor into a wide array of water column niches, such as epibenthic, semipelagic, cryopelagic and pelagic habitats. Applying stable carbon (C) and nitrogen (N) isotope analyses to gain information on feeding ecology and foraging habitats, we tested whether ecological diversification along the benthic-pelagic axis followed a single directional trend in notothenioids, or whether it evolved independently in several lineages. Population samples of 25 different notothenioid species were collected around the Antarctic Peninsula, the South Orkneys and the South Sandwich Islands. The C and N stable isotope signatures span a broad range (mean δ(13) C and δ(15) N values between -25.4‰ and -21.9‰ and between 8.5‰ and 13.8‰, respectively), and pairwise niche overlap between four notothenioid families was highly significant. Analysis of isotopic disparity-through-time on the basis of Bayesian inference and maximum-likelihood phylogenies, performed on a concatenated mitochondrial (cyt b) and nuclear gene (myh6, Ptr and tbr1) data set (3148 bp), showed that ecological diversification into overlapping feeding niches has occurred multiple times in parallel in different notothenioid families. This convergent diversification in habitat and trophic ecology is a sign of interspecific competition and characteristic for adaptive radiations.
authors.affiliation: Zoological Institute, University of Basel, Vesalgasse 1, CH-4051 Basel, Switzerland.
authors.forename: Sereina
authors.initials: S
authors.lastname: Rutschmann
authors.forename: Michael
authors.initials: M
authors.lastname: Matschiner
authors.forename: Malte
authors.initials: M
authors.lastname: Damerau
authors.forename: Moritz
authors.initials: M
authors.lastname: Muschick
authors.forename: Moritz F
authors.initials: MF
authors.lastname: Lehmann
authors.forename: Reinhold
authors.initials: R
authors.lastname: Hanel
authors.forename: Walter
authors.initials: W
authors.lastname: Salzburger
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D000864:Antarctic Regions; D001499:Bayes Theorem; D005075:Biological Evolution; D002247:Carbon Isotopes / Q000032:analysis; D017753:Ecosystem; D005399:Fishes / Q000235:genetics*; D016013:Likelihood Functions; D009587:Nitrogen Isotopes / Q000032:analysis; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes