title: RAD-seq data point to a northern origin of the arctic-alpine genus Cassiope (Ericaceae).
abstract: Many arctic-alpine plants display a highly disjunct distribution between the Arctic/Boreal regions and the southern Asian mountains. Two main hypotheses have been proposed to explain the origin of this biogeographic pattern: (1) south-to-north migration in the late Pliocene/early Pleistocene, and (2) north-to-south migration during the Miocene. The genus Cassiope is disjunctly distributed between the Arctic/Boreal regions and the Himalayan-Hengduan Mountains (HHM) and was selected to test these hypotheses. We constructed a fossil-calibrated phylogeny of Ericaceae using two plastid regions to estimate the crown group age of Cassiope, and used sequence data from thousands of loci produced by restriction site associated DNA sequencing (RAD-seq) to reconstruct the phylogeny of Cassiope. We also performed Bayesian divergence time analysis and biogeographic analysis. The Cassiope crown group was estimated to have originated in the Miocene, which predates the onset of Northern hemisphere glaciation. All HHM species formed a clade together with one eastern Siberian species, and this clade was sister to all other Arctic/Boreal species. This topology implies a northern origin of Cassiope, which is confirmed by our biogeographic analysis. Our results thus suggest that the ancient north-to-south migration hypothesis is most consistent with the origin of Cassiope.
authors.affiliation: Natural History Museum, University of Oslo, NO-0318 Oslo, Norway. Electronic address: yan.hou@nhm.uio.no.
authors.forename: Yan
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Natural History Museum, University of Oslo, NO-0318 Oslo, Norway; Science for Life Laboratory, Stockholm University, Tomtebodavägen 23, S-17165 Solna, Sweden.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Nowak
authors.affiliation: Natural History Museum, University of Oslo, NO-0318 Oslo, Norway.
authors.forename: Virginia
authors.initials: V
authors.lastname: Mirré
authors.affiliation: Natural History Museum, University of Oslo, NO-0318 Oslo, Norway.
authors.forename: Charlotte Sletten
authors.initials: CS
authors.lastname: Bjorå
authors.affiliation: Natural History Museum, University of Oslo, NO-0318 Oslo, Norway.
authors.forename: Christian
authors.initials: C
authors.lastname: Brochmann
authors.affiliation: Natural History Museum, University of Oslo, NO-0318 Oslo, Norway.
authors.forename: Magnus
authors.initials: M
authors.lastname: Popp
mesh_terms: D001110:Arctic Regions; D001483:Base Sequence; D001499:Bayes Theorem; D002681:China; D029791:Ericaceae / Q000145:classification* / Q000235:genetics*; D005580:Fossils; D049810:Genetic Speciation; D002052:Myanmar; D009390:Nepal; D010802:Phylogeny; D058974:Phylogeography; D018087:Plastids / Q000235:genetics; D017422:Sequence Analysis, DNA / Q000379:methods
keywords: Arctic/Boreal; Disjunction; Himalayan–Hengduan Mountains; RAD-seq