Molecular divergence in the eastern Asia– eastern North America disjunct section Rytidospermum of Magnolia (Magnoliaceae)

摘要: Molecular divergence in the eastern Asia-eastern North American disjunct section Rytidospermum of Magnolia was investigated by allozyme electrophoresis, chloroplast DNA (cpDNA) restriction site analysis, and gene sequencing. We calculated Nei's genetic identities between two Asian species, M. officinalis var. biloba hypoleuca, three tripetala, fraseri fraseri, macrophylla macrophylla, using frequency data from 17 nuclear-encoded loci 67 populations. then estimated cpDNA sequence five species examining variation for ten endonucleases over entire genome. Finally, nucleotide sequences rbcL were compared macrophylla. All methods consistently yielded low values tripetala its sister taxa, hypoleuca (Nei's I = 0.712 0.809, respectively; D-cpDNA 0.083% both pairs; D-rbcL 0.000% hypoleuca). The other neither which is to exhibited much higher taxa. interpreted taxa as a result recent separation (the late Miocene early Pliocene), based on time estimates molecular well geological paleoclimatic evidence. A comparison our results with those earlier studies revealed diverse array levels several pairs. Though different extinction patterns evolutionary rates may be partly responsible, this heterogeneous pattern best explained times disjunction turn suggests that floristic similarity continents most likely attained multiple migrations via Bering Atlantic land bridges, or possibly even involvement dispersal.