Taking into account phylogenetic and divergence-time uncertainty in a parametric biogeographical analysis of the Northern Hemisphere plant clade Caprifolieae

Authors

  • Stephen A. Smith

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    1. Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
    2. National Evolutionary Synthesis Center, Durham, NC, USA
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*Stephen A. Smith, National Evolutionary Synthesis Center, 2024 W. Main Street, Suite A200, Durham, NC 27705, USA. E-mail: samsmith@nescent.org

Abstract

Aim  To examine the biogeographical history of the angiosperm clade Caprifolieae (Caprifoliaceae) using parametric biogeographical reconstruction methods. The existing parametric method was extended to evaluate biogeographical reconstructions over the distribution of dated phylogenies. This method provides a framework for reconstructing large-scale biogeography with parametric methods, while accounting for uncertainty in the phylogenetic relationships and divergence time.

Location  Asia, Europe and North America.

Methods  The biogeographical history of the major lineages of Caprifolieae was reconstructed over the posterior distribution of dated trees generated from Bayesian divergence-time analyses. Results from a model with no geological constraints were compared with those from one where movement is disallowed across the North Atlantic after the Eocene. The most plausible scenarios were segregated at each node to test whether particular scenarios were reconstructed for particular divergence times. The parametric biogeographical method was also extended to estimate connectivity between areas so that the probability of dispersal between the major areas of the Northern Hemisphere could be explored.

Results  Phylogenetic results for Caprifolieae agreed with previous estimates using smaller sampling, but uncertainty remained despite efforts to resolve the relationships of the four genera within this clade using multiple markers. In addition to topological uncertainty, there were few fossils available for calibrations, resulting in large confidence intervals for divergence times. Divergence-time analyses put the diversification of Caprifolieae at between 36 and 51 Ma and showed that Caprifolieae probably originated in Asia, with multiple movements into Europe and western and eastern North America.

Main conclusions  Newly developed parametric methods for biogeographical reconstruction incorporate more data and better models. Here, the parametric biogeographical reconstruction method has been extended to allow for topological and divergence-time uncertainty. The analyses of Caprifolieae demonstrated that biogeographical hypotheses can be explored even where there are large confidence intervals on divergence times and uncertainty in topology. These results add to the growing evidence that Asia was an important source of Northern Hemisphere diversity throughout the Cenozoic.

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