Species-Level Para- and Polyphyly in DNA Barcode Gene Trees: Strong Operational Bias in European Lepidoptera

Syst. Biol. 65(6):1024–1040, 2016 © The Author(s) 2016. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact DOI:10.1093/sysbio/syw044 Advance Access publication June 10, 2016 Species-Level Para- and Polyphyly in DNA Barcode Gene Trees: Strong Operational Bias in European Lepidoptera MARKO MUTANEN1,∗ , SAMI M. KIVELÄ2 , R UTGER A. VOS3 , CAMIEL DOORENWEERD3 , SUJEEVAN R ATNASINGHAM4 , AXEL HAUSMANN5 , PETER HUEMER6 , VLAD DINCĂ4,7 , ERIK J. VAN NIEUKERKEN3 , CARLOS LOPEZ-VAAMONDE8,9 , ROGER VILA7 , LEIF AARVIK10 , THIBAUD DECAËNS11 , KONSTANTIN A. EFETOV12 , PAUL D. N. HEBERT4 , ARILD JOHNSEN10 , OLE KARSHOLT13 , MIKKO PENTINSAARI1 , R ODOLPHE R OUGERIE14 , ANDREAS SEGERER5 , GERHARD TARMANN6 , REZA ZAHIRI4,15 , AND H. CHARLES J. GODFRAY16 Received 14 December 2015; reviews returned 18 May 2016; accepted 18 May 2016 Associate Editor: Karl Kjer Abstract.—The proliferation of DNA data is revolutionizing all fields of systematic research. DNA barcode sequences, now available for millions of specimens and several hundred thousand species, are increasingly used in algorithmic species delimitations. This is complicated by occasional incongruences between species and gene genealogies, as indicated by situations where conspecific individuals do not form a monophyletic cluster in a gene tree. In two previous reviews, nonmonophyly has been reported as being common in mitochondrial DNA gene trees. We developed a novel web service “Monophylizer” to detect non-monophyly in phylogenetic trees and used it to ascertain the incidence of species nonmonophyly in COI (a.k.a. cox1) barcode sequence data from 4977 species and 41,583 specimens of European Lepidoptera, the largest data set of DNA barcodes analyzed from this regard. Particular attention was paid to accurate species identification to ensure data integrity. We investigated the effects of tree-building method, sampling effort, and other methodological issues, all of which can influence estimates of non-monophyly. We found a 12% incidence of non-monophyly, a value significantly lower than that observed in previous studies. Neighbor joining (NJ) and maximum likelihood (ML) methods yielded almost equal numbers of non-monophyletic species, but 24.1% of these cases of non-monophyly were only found by one of these methods. Non-monophyletic species tend to show either low genetic distances to their nearest neighbors or exceptionally high levels of intraspecific variability. Cases of polyphyly in COI trees arising as a result of deep intraspecific divergence are negligible, as the detected cases reflected misidentifications or methodological errors. Taking into consideration variation in sampling effort, we estimate that the true incidence of non-monophyly is ∼23%, but with operational factors still being included. Within the operational factors, we separately assessed the frequency of taxonomic limitations (presence of overlooked cryptic and oversplit species) and identification uncertainties. We observed that operational factors are potentially present in more than half (58.6%) of the detected cases of non-monophyly. Furthermore, we observed that in about 20% of non-monophyletic species and entangled species, the lineages involved are either allopatric or parapatric—conditions where species delimitation is inherently subjective and particularly dependent on the species concept that has been adopted. These observations suggest that species-level non-monophyly in COI gene trees is less common than previously supposed, with many cases reflecting misidentifications, the subjectivity of species delimitation or other operational factors. [DNA barcoding; gene tree; Lepidoptera; mitochondrial COI; mitochondrial cox1; paraphyly; polyphyly; species delimitation; species monophyly.] There has been endless debate over the definition of a species and whether the concept has any biological reality (Wheeler and Meier 2000; De Queiroz 2007; Mallet 2007; Hausdorf 2011). While there is now a broad consensus that more inclusive taxonomic categories are defined solely following cladistic principles (Hennig 1966) (i.e., by monophyly criterion and hierarchical order) and are largely arbitrary, species are generally viewed as natural entities with observable distances between them, resulting from the differentiation of lineages through speciation (Wright 1940; Mayr 1942; Coyne and Orr 2004). However, species boundaries are often much harder to discern when individuals are sampled across geographical scales or through time (Baselga et al. 2013), and the complexity in gathering direct evidence on the potential for interbreeding creates challenges for rigorous testing of species boundaries. Nonetheless, the species rank has maintained its status as a central concept in virtually all fields of biology, one with particular societal relevance because of its centrality in conservation, legislation, or food trade (e.g., Avise 1989; Isaac et al. 2004). Although there are species 1024 1 Department of Genetics and Physiology, University of Oulu, Finland; 2 Department of Ecology, University of Oulu, Finland; 3 Naturalis Biodiversity Center, Leiden, The Netherlands; 4 Centre for Biodiversity Genomics, Biodiversity Institute of Ontario, University of Guelph, Canada; 5 SNSB – Bavarian State Collection of Zoology, Munich, Germany; 6 Tiroler Landesmuseen-Betriebsgesellschaft m.b.H., Innsbruck, Austria; 7 Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain; 8 INRA, UR633 Zoologie Forestière, 45075 Orléans, France; 9 Institut de Recherche sur la Biologie de l’Insecte, CNRS UMR 7261, Université François-Rabelais de Tours, UFR Sciences et Techniques, 37200 Tours, France 10 Natural History Museum University of Oslo, Norway; 11 Centre d’Écologie Fonctionnelle et Évolutive, UMR 5175 CNRS / University of Montpellier / University of Montpellier 3 / EPHE / SupAgro Montpellier / INRA / IRD, 1919 Route de Mende, 34293 Montpellier Cedex 5, France; 12 Crimean Federal University, Simferopol, Crimea; 13 Zoologisk Museum, Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen Ø, Denmark; 14 Département Systématique et Evolution, Muséum National d’Histoire Naturelle, Institut de Systématique, Evolution, Biodiversité, ISYEB–UMR 7205 MNHN, CNRS, UPMC, EPHE, Sorbonne Universités, Paris, France; 15 Ottawa Plant Laboratory, Canadian Food Inspection Agency, Canada; 16 Department of Zoology, University of Oxford, UK; ∗ Correspondence to be sent to: Department of Genetics and Physiology, University of Oulu, PO Box 3000, Oulu FI-90014, Finland; E-mail: marko.mutanen@ou (...truncated)