How diverse is Mitopus morio? Integrative taxonomy detects cryptic species in a small-scale sample of a widespread harvestman WOLFGANG ARTHOFER,* 1 HANNES RAUCH,* 1 BARBARA THALER-KNOFLACH,* KARL MODER, † CHRISTOPH MUSTER, ‡ BIRGIT C. SCHLICK-STEINER* 2 and FLORIAN M. STEINER* 2 *Molecular Ecology Group, Institute of Ecology, University of Innsbruck, Technikerstrasse 25, 6020, Innsbruck, Austria, †Institute of Mathematics and Applied Statistics, Department of Spatial, Landscape, and Infrastructure Sciences, University of Natural Resources and Life Sciences, Peter Jordan-Strasse 82, 1180, Vienna, Austria, ‡General Zoology and Zoological Systematics, Zoological Institute and Museum, University of Greifswald, Johann Sebastian Bach-Str 11/12, 17487, Greifswald, Germany Abstract Mitopus morio is a widespread harvestman species occurring in most of Europe and in moderate and cold-moderate zones of Asia and North America. The species is charac- terized by extreme variability in body size and leg length. As leg length is correlated with habitat temperature, M. morio has been considered as an example of Allen’s rule. Recently, observations for a single location in Tyrol, Austria, indicated the absence of mating between short- and long-legged individuals. This study examines for signs of putative cryptic species in M. morio using an integrative approach that combines mat- ing trials, amplified fragment length polymorphism whole-genome scans, mitochon- drial sequences and morphometrics. The mating trials did not corroborate the initial hypothesis of a reproductive barrier associated with leg size. Both types of genetic data revealed the existence of three distinct groups, in line with the mating results but lar- gely unrelated to leg morphology and geographical origin of specimens. Morphometric characters supporting the findings of the other disciplines were identified using a supervised approach. We infer from all data together the existence of strongly diverged cryptic lineages among the analysed individuals, cautiously interpret them as three sympatric species and conclude that in these harvestmen Allen’s rule applies at differ- ent levels. Due to the unexpected amount of differentiation found within a geographi- cal scale very small compared with the distribution of M. morio, we suggest a thorough revision of the genus prior to formal taxonomic changes. Our case study underlines the general applicability of the integrative taxonomic protocol used and highlights the relevance of several rationales implemented in the protocol. Keywords: AFLP, Allen’s rule, cryptic species, integrative taxonomy, Mitopus morio, mtDNA Received 15 May 2012; revision received 4 April 2013; accepted 8 April 2013 Introduction The Holarctic harvestman Mitopus morio (Fabricius, 1779) is the most widespread species of Opiliones. It occurs in cold temperate parts of North America and Europe, including Greenland and Iceland, in Siberian coniferous zones and in Palaearctic regions of Japan and China. Its vertical distribution ranges from sea level up to locally more than 3000 m above sea level (Mar- tens 1978). Mitopus morio exhibits high variability in body size and absolute as well as relative leg lengths (Hillyard & Sankey 1989). Resulting from this variabil- ity, more than ten species were described, which are currently considered as junior synonyms of M. morio (Jennings 1983; Hillyard & Sankey 1989). The leg Correspondence: Wolfgang Arthofer, Fax: +43 512 507 51799; E-mail: wolfgang.arthofer@uibk.ac.at 1 equally contributing first authors 2 equally contributing senior authors © 2013 Blackwell Publishing Ltd Molecular Ecology (2013) doi: 10.1111/mec.12340