Leijs, R.van Nes, E.Watts, C.Cooper, S.Humphreys, W.Hogendoorn, K.Hansson, B.2012-09-032012-09-032012PLoS One, 2012; 7(3):1-81932-62031932-6203http://hdl.handle.net/2440/72976Evidence is growing that not only allopatric but also sympatric speciation can be important in the evolution of species. Sympatric speciation has most convincingly been demonstrated in laboratory experiments with bacteria, but field-based evidence is limited to a few cases. The recently discovered plethora of subterranean diving beetle species in isolated aquifers in the arid interior of Australia offers a unique opportunity to evaluate alternative modes of speciation. This naturally replicated evolutionary experiment started 10-5 million years ago, when climate change forced the surface species to occupy geographically isolated subterranean aquifers. Using phylogenetic analysis, we determine the frequency of aquifers containing closely related sister species. By comparing observed frequencies with predictions from different statistical models, we show that it is very unlikely that the high number of sympatrically occurring sister species can be explained by a combination of allopatric evolution and repeated colonisations alone. Thus, diversification has occurred within the aquifers and likely involved sympatric, parapatric and/or microallopatric speciation.enCopyright: © 2012 Leijs et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.AnimalsModels, StatisticalBayes TheoremReproducibility of ResultsAnimal MigrationEcosystemPhylogenySpecies SpecificityGeographyModels, GeneticAustraliaGenetic SpeciationBiological EvolutionColeopteraJournal article002011815410.1371/journal.pone.00342600003053391001412-s2.0-8485913405725016Cooper, S. [0000-0002-7843-8438]Hogendoorn, K. [0000-0002-4942-8062]