Zhen-Wen Liu1, Diana D Jolles2, Jing Zhou3, Hua Peng4, Richard I Milne5. 1. Key Laboratory for Plant Diversity and Biogeography of East Asia, Kuming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China zhenwen1980@hotmail.com. 2. Rancho Santa Ana Botanic Garden, Claremont Graduate University, 1500 North College Avenue, Claremont, CA 91711, USA. 3. School of Pharmaceutical Science & Yunnan Key Laboratory of Pharmacology for Natural Products, Kunming Medical University, 1168 Western Chunrong Road, Yuhua Street, Chenggong New City, Kunming 650500, China. 4. Key Laboratory for Plant Diversity and Biogeography of East Asia, Kuming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China. 5. Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JH, UK.
Abstract
BACKGROUND AND AIMS: In the Northern Hemisphere, Tertiary relict disjunctions involve older groups of warm affinity and wide disjunctions, whereas circumboreal distributions in Arctic-Alpine taxa tend to be younger. Arctic-Alpine species are occasionally derived from Tertiary relict groups, but Pyrola species, in particular, are exceptional and they might have occurred multiple times. The aim of this study was to reconstruct the biogeographic history of Pyrola based on a clear phylogenetic analysis and to explore how the genus attained its circumboreal distribution. METHODS: Estimates of divergence times and ancestral geographical distributions based on neutrally evolving DNA sequence variation were used to develop a spatio-temporal model of colonization patterns for Pyrola. KEY RESULTS: Pyrola originated and most diversification occurred in Asia; North America was reached first by series Scotophyllae in the late Miocene, then by sub-clades of series Pyrola and Ellipticae around the Pliocene. The three circumboreal taxa, P. minor, P. chlorantha and the P. rotundifolia complex, originated independently of one another, with the last two originating in Asia. CONCLUSIONS: Three circumboreal Pyrola lineages have arisen independently and at least two of these appear to have originated in Asia. The cool, high-altitude habitats of many Pyrola species and the fact that diversification in the genus coincided with global cooling from the late Miocene onwards fits a hypothesis of pre-adaptation to become circumboreal within this group.
BACKGROUND AND AIMS: In the Northern Hemisphere, Tertiary relict disjunctions involve older groups of warm affinity and wide disjunctions, whereas circumboreal distributions in Arctic-Alpine taxa tend to be younger. Arctic-Alpine species are occasionally derived from Tertiary relict groups, but Pyrola species, in particular, are exceptional and they might have occurred multiple times. The aim of this study was to reconstruct the biogeographic history of Pyrola based on a clear phylogenetic analysis and to explore how the genus attained its circumboreal distribution. METHODS: Estimates of divergence times and ancestral geographical distributions based on neutrally evolving DNA sequence variation were used to develop a spatio-temporal model of colonization patterns for Pyrola. KEY RESULTS: Pyrola originated and most diversification occurred in Asia; North America was reached first by series Scotophyllae in the late Miocene, then by sub-clades of series Pyrola and Ellipticae around the Pliocene. The three circumboreal taxa, P. minor, P. chlorantha and the P. rotundifolia complex, originated independently of one another, with the last two originating in Asia. CONCLUSIONS: Three circumboreal Pyrola lineages have arisen independently and at least two of these appear to have originated in Asia. The cool, high-altitude habitats of many Pyrola species and the fact that diversification in the genus coincided with global cooling from the late Miocene onwards fits a hypothesis of pre-adaptation to become circumboreal within this group.
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