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Ingrid Olivares1 Sren Faurby2 Rodrigo Cmara-Leret1 Alex Pigot3

1 Department of Systematic and Evolutionary Botany, University of Zurich, Switzerland 2 Department of Biological & Environmental Sciences, University of Gothenburg, Sweden 3 Centre for Biodiversity and Environment Research, University College London

Linking phylogenies to the geographical distribution of a lineage allows inferring the geographical mode of speciation. Here, we used the geographical distribution of sister species and their estimated divergence times to infer if there is a predominant mode of geographical speciation (allopatry or sympatry) in two diverse groups of plants from tropical (palms) and temperate regions (pines). We selected two approaches previously used to infer the mode of speciation in vertebrates: 1) the proportion of sister species showing zero and complete range overlap, and 2) a modelling framework that calculates the probability that a sister species pair exists in its current geographical state (i.e., allopatry or sympatry). In contrast to birds, for which the first indicator shows that sympatric speciation accounts for only 5% of speciation events, our results hint towards a greater role of sympatric speciation (ca. 3045%) in palms and pines. We further find that palms and pines can diverge through either allopatry or sympatry and undergo reverse transitions back to the initial state. In contrast, previous studies showed that the best suited model for primates, amphibians, and birds is one in which species diverge exclusively in allopatry and then undergo an irreversible transition to sympatry. Our work therefore suggests that the sympatric speciation of Howea palms might not be an exceptional case, but rather, that sympatric speciation might be an important mode of plant speciation in palms and other plant families.