QUANTIFYING THE PLEISTOCENE HISTORY OF THE OAK GALL PARASITOID CECIDOSTIBA FUNGOSA USING TWENTY INTRON LOCI |
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Authors: | Konrad Lohse Barbara Sharanowski Graham N Stone |
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Institution: | 1. Institute of Evolutionary Biology, University of Edinburgh, King's Buildings, West Mains Road, EH9 3JT, United Kingdom;2. E‐mail: konrad.lohse@gmail.com;3. Department of Entomology, North Carolina State University, 2317 Gardner Hall, Campus Box 7613, Raleigh, North Carolina 27695 |
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Abstract: | The longitudinal spread of temperate organisms into refugial populations in Southern Europe is generally assumed to predate the last interglacial. However, few studies have attempted to quantify this process in nonmodel organisms using explicit models and multilocus data. We used sequence data for 20 intron‐spanning loci (12 kb per individual) to resolve the history of refugial populations of a widespread western Palaearctic oak gall parasitoid Cecidostiba fungosa (Pteromalidae). Using maximum likelihood and Bayesian methods we assess alternative population tree topologies and estimate divergence times and ancestral population sizes under a model of divergence between three refugia (Middle East, Balkans and Iberia). Both methods support an “Out of the East” history for C. fungosa, matching the pattern previously inferred for their gallwasp hosts. However, coalescent‐based estimates of the ages of population divides are much more recent (coinciding with the Eemian interglacial) than nodal ages of single gene trees for C. fungosa and other species. We also find that increasing the sample size from one haploid sequence per refugial population to three only marginally improves parameter estimates. Our results suggest that there is significant information in the minimal samples currently analyzable with maximum likelihood methods, and that similar methods could be applied to multiple species to test alternative models of assemblage evolution. |
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Keywords: | Ancestral population size coalescent theory parasitoid assemblages population divergence times statistical phylogeography |
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