Supraspecies phylogenetic relationships in the subfamily Arvicolinae (voles and lemmings): nuclear versus mitochondrial genes. Could hard polytomies be resolved? N.I. Abramson Zooological Institute, Russian Academy of Sciences

Overview of the talk What are arvicolids and why they present an excellent model to test evolutionary and phylogenetic hypotheses and approaches to phylogeny recovery Brief historical background Material and methods Unexpected results of molecular research in phylogeny reconstruction Mitochondrial versus nuclear genes Could hard polytomies be resolved? Molecular data in paleontological context

Subfamily Arvicolinae (voles and lemmings)

Arvicolinae as a model  one of the most young and species rich groups of Muroidea (over 100 known species).  widely distributed in all landscape types in the temperate and arctic zones of the Northern Hemisphere  unprecedented paleontological record, rapid evolution rate, and continuous diversification  morphological, cytogenetic, biochemical and molecular data sets available

BRIEF HISTORICAL BACKGROUND

Journal of Mammalian Evolution, Vol. 6, No. 3, 1999 MtDNA Evidence for Repeated Pulses of Speciation Within Arvicoline and Murid Rodents Chris J. Conroy and Joseph A. Cook1 Mitochondrial phylogeny of Arvicolinae using comprehensive taxonomic sampling yields new insights ELENA V. BUZAN, BORIS KRYSTUFEK, BERND HÄNFLING2 and WILLIAM F. HUTCHINSON The evolutionary radiation of Arvicolinae rodents (voles and lemmings): relative contribution of nuclear and mitochondrial DNA Phylogenies Thomas Galewski et al.

Objective To separate the phyletic lineages that diverged during the basal (first) radiation wave from the groups arising at the later steps of the evolution of Arvicolinae

Material and methods 21 vole species belonging to 14 (out of 28) genera of eight (out of ten) tribes Vole tribes Ellobiusini and Lagurini, which were not examined before, and whose phylogenetic positions are questionable Akodon (Sigmodontinae), Peromyscus (Neotominae), and Cricetulus (Cricetinae), used as an outgroup The sample includes : Molecular markers : GHR, 10 exon, 921 bp; LCAT, 612 bp: exons 2-5; introns, 330 bp Phylogenetic analysis : MP for both the concatenated matrix and the two separate genes ML for exons for both genes Bayesian analysis Relaxed molecular clock, using the Bayesian algorithm of the Multidivtime package( BRCA1, RAG1,IRBP,and cmyc)

Results III I I wave II wave III wave

Results Chronogram of radiation in the subfamily Arvicolinae. The divergence time corresponds to the mean a posteriori estimate of the age. Gray bars show the confidence intervals of the nodes. Myodini Lagurini Ellobiusini Arvicolini

Mitochondrial versus nuclear genes Cyt b Buzan et al., 2008

Possible evolutionary scenario

Morphological and paleontological evidence

Molecular data in paleontological context  The first radiation wave Our results suggest that basal subfamily radiation occurred in the late Miocene, which is in accordance with paleontological data indicating that the most primitive undoubted members of the group appeared about 7.0 million years ago in Pon tic deposits of eastern Europe  The second radiation wave. This step corresponds to the divergence of the ancestors of modern Myodini. The divergence time corresponds to the Late Miocene–Early Pliocene according to molecular data. Our findings indicate that Myodini diverged from the common branch of Arvicolinae after the first (basal) radiation wave but before Lagurini/Ellobiusini/Arvicolini radiation. The distribution of modern species and paleontological findings indicate that the group originates from East Asia and that level and highland forests were its initial habitats.  The third radiation wave of Arvicolinae includes the divergence of Lagurini/Ellobiusini/Arvicolini. The divergence dates back to the Early Pliocene according to our results. This means that Palearctic voles of a pro-Mimomys organization level might be a common ancestor of the group. Lagurini and Arvicolini developed along the main evolutionarily pathway of the subfamily, gradually adapting to eating vegetative parts of grasses and colonizing predominantly meadow (Arvicolini) and steppe (Lagurini) landscapes. Ellobiusini provide a remarkable example of rapid evolutionary changes associated with the adaptation to subterranean life; in particular, they preserved the primitive molar structure, while their cranium and limbs were changed. Rapid adaptive evolution explains why it is difficult to infer the phylogennetic position of Ellobiusini from classical morphological data

Aknowledgements This work is coauthored by Vladimir Lebedev, Anna Bannikova and Alexei Tesakov A.S. Smorktcheva provide invaluable material on yellow steppe vole A.Kostygov, E.Rodchenkova, T.Petrova & S.Bodrov assist in the laboratory Financial support was provided by RFFI grant and Programs of Fundamental Research RAS: “Biosphere Origin and Evolution” and “Biodiversity”