Abstract
Closely related species with a worldwide distribution provide an opportunity to understand evolutionary and biogeographic processes at a global scale. Hazel (Corylus) is an economically important genus of tree and shrub species found in temperate regions of Asia, North America and Europe. Here we use multiple nuclear and chloroplast loci to estimate a time-calibrated phylogenetic tree of the genus Corylus. We model the biogeographic history of this group and the evolutionary history of tree and shrub form. We estimate that multiple Corylus lineages dispersed long distances between Europe and Asia and colonised North America from Asia in multiple independent events. The geographic distribution of tree versus shrub form of species appears to be the result of 4–5 instances of convergent evolution in the past 25 million years. We find extensive discordance between our nuclear and chloroplast trees and potential evidence for chloroplast capture in species with overlapping ranges, suggestive of past introgression. The important crop species C. avellana is estimated to be closely related to C. maxima, C. heterophylla var. thunbergii and the Colurnae subsection. Our study provides a new phylogenetic hypothesis or Corylus and reveals how long-distance dispersal can shape the distribution of biodiversity in temperate plants.
Highlights
Related species with a worldwide distribution provide an opportunity to understand evolutionary and biogeographic processes at a global scale
Ancestral biogeographic estimation methods can be used to model these historical patterns and typically separate cladogenesis into three types: where the new species occupy the same range as their ancestors, where a new species occupies a subset of the ancestral range or where speciation occurs as a result of a vicariance event
Fossil calibrations allow the estimation of a detailed temporal scale of diversification in hazel, with most divergence events taking place in the Miocene
Summary
Related species with a worldwide distribution provide an opportunity to understand evolutionary and biogeographic processes at a global scale. Hazel (Corylus) is an economically important genus of tree and shrub species found in temperate regions of Asia, North America and Europe. Long distance dispersal events can provide sufficient isolation from the ancestral population for a new lineage to diverge, potentially leading to speciation. Such founder-event speciation[4,5] (which is not necessarily the result of founder effects) may play an important role in generating species diversity, especially in clades that are present worldwide, having presumably spread far from a single point of origin. Understanding the evolutionary history of this genus is important from both a scientific and economic standpoint
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