Axel L. Schönhofer

Phylogenomic Resolution of Paleozoic Divergences in Harvestmen (Arachnida, Opiliones) via Analysis of Next-Generation Transcriptome Data

Next-generation sequencing technologies are rapidly transforming molecular systematic studies of non-model animal taxa. The arachnid order Opiliones (commonly known as “harvestmen”) includes more than 6,400 described species placed into four well-supported lineages (suborders). Fossil plus molecular clock evidence indicates that these lineages were diverging in the late Silurian to mid-Carboniferous, with some fossil harvestmen representing the earliest known land animals. Perhaps because of this ancient divergence, phylogenetic resolution of subordinal interrelationships within Opiliones has been difficult. We present the first phylogenomics analysis for harvestmen, derived from comparative RNA-Seq data for eight species representing all suborders. Over 30 gigabases of original Illumina short-read data were used in de novo assemblies, resulting in 50–80,000 transcripts per taxon. Transcripts were compared to published scorpion and tick genomics data, and a stringent filtering process was used to identify over 350 putatively single-copy, orthologous protein-coding genes shared among taxa. Phylogenetic analyses using various partitioning strategies, data coding schemes, and analytical methods overwhelmingly support the “classical” hypothesis of Opiliones relationships, including the higher-level clades Palpatores and Phalangida. Relaxed molecular clock analyses using multiple alternative fossil calibration strategies corroborate ancient divergences within Opiliones that are possibly deeper than the recorded fossil record indicates. The assembled data matrices, comprising genes that are conserved, highly expressed, and varying in length and phylogenetic informativeness, represent an important resource for future molecular systematic studies of Opiliones and other arachnid groups.

Hidden Mediterranean diversity: Assessing species taxa by molecular phylogeny within the opilionid family Trogulidae (Arachnida, Opiliones)

This is the first comprehensive study to evaluate the relationships between the western palearctic harvestman families Dicranolasmatidae, Trogulidae and Nemastomatidae with focus on the phylogeny and systematics of Trogulidae, using combined sequence data of the nuclear 28S rRNA and the mitochondrial cytochrome b gene. Bayesian analysis and Maximum parsimony do not reliably resolve Dicranolasma as distinct family but place it on a similar phylogenetic level as several lineages of Trogulidae. Nemastomatidae and Trogulidae turned out to be monophyletic, as did genera Anelasmocephalus and Trogulus within the Trogulidae. The genera Calathocratus, Platybessobius and Trogulocratus each appeared para or polyphyletic, respectively and are synonymized with Calathocratus. The monotypic genus Kofiniotis is well supported. We show molecular data to be in general concordance with taxa characterized by morphology. Molecular data are especially useful to calibrate morphological characters for systematic purposes within homogeneous taxa. In the majority of closely related valid species we show the lowest level of genetic distance to be not lower than 5%. By this threshold in terms of traditionally accepted species the estimated number of species turns out to be 1.5-2.4 times higher than previously believed. With respect to European fauna cryptic diversity in Trogulidae is obviously extraordinarily high and hitherto largely underestimated.

A taxonomic catalogue of the Dyspnoi Hansen and Sørensen, 1904 (Arachnida: Opiliones)

An update of the systematics and determination key of the Opiliones suborder Dyspnoi is provided. The included catalogue represents the first comprehensive species and synonymy listing since Roewer (1923). It summarises all taxonomic changes to date and attempts to be a sound basis against the exponential growing number of online errors, for which examples are given. Species taxonomy features most obvious changes within the Nemastomatidae. The number of species in the collective genus Nemastoma is reduced from 96 (Hallan 2005) to its sensu stricto definition of 7, and the excluded names are transferred to other genera or considered as nomina dubia, predominantly in Paranemastoma. The systematics of the superfamily Ischyropsalidoidea is discussed and family-level diagnoses are renewed to support taxonomical changes: The morphological heterogeneity in the Sabaconidae is resolved by reverting the family to its original monogeneric state. Taracus and Hesperonemastoma are separated as Taracidae fam. n., and Crosbycus is tentatively transferred to this assembly. The remaining genera of Ceratolasmatidae, Acuclavella and Ceratolasma, are included as subfamily Ceratolasmatinae in the Ischyropsalididae and Ischyropsalis is assigned subfamily status, respectively. Other nomenclatural acts are restricted to species-group level with the following synonymies established: Sabacon jonesi Goodnight & Goodnight, 1942 syn. n. (=cavicolens (Packard, 1884)), Dicranolasma diomedeum Kulczyński, 1907 syn. n. (=hirtum Loman, 1894), Mitostoma (Mitostoma) sketi Hadži, 1973a syn. n. (=chrysomelas (Hermann, 1804)), Mitostoma asturicum Roewer, 1951 syn. n. (=pyrenaeum (Simon, 1879a)), Nemastoma formosum Roewer, 1951 syn. n. (=Nemastomella bacillifera bacillifera (Simon, 1879a)), Nemastoma reimoseri Roewer, 1951 syn. n. (=Paranemastoma bicuspidatum (C.L. Koch, 1835)), Nemastoma tunetanum Roewer, 1951 syn. n. (=Paranemastoma bureschi (Roewer, 1926)), Phalangium flavimanum C.L. Koch, 1835 syn. n. (=Paranemastoma quadripunctatum (Perty, 1833)), Crosbycus graecus Giltay, 1932 syn. n. (=Paranemastoma simplex (Giltay, 1932)), Nemastoma bimaculosum Roewer 1951 syn. n. (=Paranemastoma titaniacum (Roewer, 1914)), Trogulocratus tunetanus Roewer, 1950 syn. n. (=Calathocratus africanus (Lucas, 1849)), Trogulus albicerus Sø-rensen, 1873 syn. n. (=Calathocratus sinuosus (Sørensen, 1873)), Metopoctea exarata Simon, 1879a syn. n. (=Trogulus aquaticus Simon, 1879a), Trogulus galasensis Avram, 1971 syn. n. (=Trogulus nepaeformis (Scopoli, 1763)) and Trogulus roeweri Avram, 1971 syn. n. (=Trogulus nepaeformis (Scopoli, 1763)). Paranemastoma werneri (Kulczyński, 1903) is elevated from subspecies to species. Ischyropsalis luteipes Simon, 1872b is proposed as nomen protectum, taking precedence over Lhermia spinipes Lucas 1866 nomen oblitum. The same accounts for Anelasmocephalus cambridgei (Westwood, 1874) nomen protectum, taking precedence over Trogulus violaceus Gervais, 1844 nomen oblitum, Trogulus closanicus Avram, 1971 nomen protectum over Trogulus asperatus C.L. Koch, 1839a nomen oblitum, as well as Trogu-lus martensi Chemini, 1983 nomen protectum over Trogulus tuberculatus Canestrini, 1874 nomen oblitum. New combinations, all from Nemastoma, are Histricostoma anatolicum (Roewer, 1962), Mediostoma globuliferum (L. Koch, 1867), Nemastomella hankiewiczii (Kulczyński, 1909), Nemastomella maarebense (Simon, 1913), Nemastomella monchiquense (Kraus, 1961) and Paranemastoma simplex (Giltay, 1932); from Mitostoma: Nemastomella armatissima (Roewer, 1962). Revived combinations are Nemastomella cristinae (Rambla, 1969) (from Nemastoma) and Nemastomella sexmucronatum (Simon, 1911) (from Nemastoma). The following Nemastoma are transferred to Paranemastoma but suggested as nomina dubia: aeginum (Roewer, 1951), amuelleri (Roewer, 1951), bolei (Hadži, 1973a), caporiaccoi (Roewer, 1951), carneluttii (Hadži, 1973a), ferkeri (Roewer, 1951), gigas montenegrinum (Nosek, 1904), gostivarense (Hadži, 1973a), ikarium (Roewer, 1951), quadripunctatum ios (Roewer, 1917), kaestneri (Roewer, 1951), longipalpatum (Roewer, 1951), macedonicum (Hadži, 1973a), multisignatum (Hadži, 1973a), nigrum (Hadži, 1973a), perfugium (Roewer, 1951), santorinum (Roewer, 1951), senussium (Roewer, 1951), sketi (Hadži, 1973a), spinosulum (L. Koch, 1869). Further suggested nomina dubia are Trogulus coreiformis C.L. Koch, 1839a, Trogulus lygaeiformis C.L. Koch, 1839a and Trogulus templetonii Westwood, 1833.

Molecular phylogeny of the harvestmen genus Sabacon (Arachnida: Opiliones: Dyspnoi) reveals multiple Eocene–Oligocene intercontinental dispersal events in the Holarctic

We investigated the phylogeny and biogeographic history of the Holarctic harvestmen genus Sabacon, which shows an intercontinental disjunct distribution and is presumed to be a relatively old taxon. Molecular phylogenetic relationships of Sabacon were estimated using multiple gene regions and Bayesian inference for a comprehensive Sabacon sample. Molecular clock analyses, using relaxed clock models implemented in BEAST, are applied to date divergence events. Biogeographic scenarios utilizing S-DIVA and Lagrange C++ are reconstructed over sets of Bayesian trees, allowing for the incorporation of phylogenetic uncertainty and quantification of alternative reconstructions over time. Four primary well-supported subclades are recovered within Sabacon: (1) restricted to western North America; (2) eastern North American S. mitchelli and sampled Japanese taxa; (3) a second western North American group and taxa from Nepal and China; and (4) eastern North American S. cavicolens with sampled European Sabacon species. Three of four regional faunas (wNA, eNA, East Asia) are thereby non-monophyletic, and three clades include intercontinental disjuncts. Molecular clock analyses and biogeographic reconstructions support nearly simultaneous intercontinental dispersal coincident with the Eocene-Oligocene transition. We hypothesize that biogeographic exchange in the mid-Tertiary is likely correlated with the onset of global cooling, allowing cryophilic Sabacon taxa to disperse within and among continents. Morphological variation supports the divergent genetic clades observed in Sabacon, and suggests that a taxonomic revision (e.g., splitting Sabacon into multiple genera) may be warranted.

Revision of the genus Trogulus Latreille: the Trogulus coriziformis species-group of the western Mediterranean (Opiliones : Trogulidae)

Within the well researched European fauna of harvestmen, the genus Trogulus Latreille exhibits unexpectedly high cryptic diversity. The species’ uniform morphology hinders an exclusively morphological approach to their systematics and taxonomy, and a preliminary molecular study estimated the number of species to be three times higher than currently known. The current study focuses on a clearly defined species-group within Trogulus, combining molecular (~1700 bp 28S rRNA and the cytochrome b gene), distributional, morphometric and morphological data. Relationships are reconstructed using Bayesian inference, maximum parsimony and maximum likelihood and this information is subsequently used to evaluate morphological characters for systematic usability and to identify biogeographical processes leading to speciation events. The Trogulus coriziformis species-group is defined and diagnosed and includes eight species. Three species are redefined: T. coriziformis C. L. Koch, 1839, for which a neotype is designated, and T. aquaticus Simon, 1879 and T. cristatus Simon, 1879 for which lectotypes are designated. Four species are described as new: T. balearicus, sp. nov. from the Balearic Islands, T. huberi, sp. nov. from southern Portugal, T. prietoi, sp. nov. from Andalusia, Spain, and T. pyrenaicus, sp. nov. from the central Pyrenees. Trogulus lusitanicus Giltay, 1931 is used as collective name and probably refers to a composite of species presently difficult to tell apart. Trogulus salfii De Lerma, 1948 is proposed as a synonym for T. coriziformis. Within Trogulus, the molecular genetic data support monophyly and basal placement of the Trogulus coriziformis species-group. The species to differ in external morphology (size, papillation of palps, apophyses of legs, pattern of body papillation, morphometric data), 28S and cytochrome b autapomorphies and to a lesser degree by male genital morphology. The species-group is confined to the western Mediterranean area and its species are allopatrically distributed. Their present distribution corresponds to geological processes in the Miocene and Pliocene indicating that this group of organisms may be of considerable value for further biogeographic studies.

Phylogenetic relationships of the spider family Psechridae inferred from molecular data, with comments on the Lycosoidea (Arachnida : Araneae)

Abstract. We investigated the relative phylogenetic position of the spider genera Psechrus Thorell, 1878 and Fecenia Simon, 1887 comprising the family Psechridae Simon, 1890 within the order Araneae (plus 50 outgroup taxa) using molecular data of the nuclear 28S rRNA gene and the mitochondrial cytochrome c oxidase subunit I (COI) gene. We further revised the placement of genera formerly hypothesised in Psechridae and tested morphological species and species-group hypotheses recently proposed for Psechrus and Fecenia. Our results showed both genera as monophyletic and included within Lycosoidea but indicated no support for a monophyletic family Psechridae. Support for relationships to particular genera of other families (Lycosidae, Pisauridae) was found to be equally low. Previous removal of the genera Stiphidion Simon, 1902, Poaka Forster & Wilton, 1973, Tengella Dahl, 1901 (Metafecenia F. O. Pickard-Cambridge, 1902) and Themacrys Simon, 1906 from Psechridae is confirmed by recovering most of them outside Lycosoidea. For Tengella (part of Lycosoidea) a close relation to Psechridae is not supported. In the species-rich genus Psechrus, morphologically predefined species groups were generally recovered as monophyletic. COI information was applied to test the morphological species hypotheses for 28 Psechridae species, most of them represented by more than one specimen. Our analyses corroborated all proposed species and indicated COI as reliable for barcoding both Psechrus and Fecenia. COI enabled assignment of a juvenile specimen to Fecenia protensa, establishing the first species record for Brunei.

Gluing the ‘unwettable’: soil-dwelling harvestmen use viscoelastic fluids for capturing springtails

Gluing can be a highly efficient mechanism of prey capture, as it should require less complex sensory–muscular feedback. Whereas it is well known in insects, this mechanism is much less studied in arachnids, except spiders. Soil-dwelling harvestmen (Opiliones, Nemastomatidae) bear drumstick-like glandular hairs (clavate setae) at their pedipalps, which were previously hypothesized to be sticky and used in prey capture. However, clear evidence for this was lacking to date. Using high-speed videography, we found that the harvestman Mitostoma chrysomelas was able to capture fast-moving springtails (Collembola) just by a slight touch of the pedipalp. Adhesion of single clavate setae increased proportionally with pull-off velocity, from 1 μN at 1 μm s−1 up to 7 μN at 1 mm s−1, which corresponds to the typical weight of springtails. Stretched glue droplets exhibited characteristics of a viscoelastic fluid forming beads-on-a-string morphology over time, similar to spider capture threads and the sticky tentacles of carnivorous plants. These analogies indicate that viscoelasticity is a highly efficient mechanism for prey capture, as it holds stronger the faster the struggling prey moves. Cryo-scanning electron microscopy of snap-frozen harvestmen with glued springtails revealed that the gluey secretions have a high affinity to wet the microstructured cuticle of collembolans, which was previously reported to be barely wettable for both polar and non-polar liquids. Glue droplets can be contaminated with the detached scaly setae of collembolans, which may represent a counter-adaptation against entrapment by the glue, similar to the scaly surfaces of Lepidoptera and Trichoptera (Insecta) facilitating escape from spider webs.

The enigmatic Alpine opilionid Saccarella schilleri gen. n., sp. n. (Arachnida: Nemastomatidae)—isolated systematic placement inferred from comparative genital morphology

In Opiliones, male genital morphology plays a key role in systematics and understanding the evolution of the group because functional modifications often outline higher taxonomic levels. In Nemastomatidae, different lateral stabilizing structures on the penial truncus cane developed independently. These wing-like protuberances serve as anchor points for two muscular tendons and are interpreted traditionally as generic characters. A newly discovered species from Monte Saccarello in the Ligurian Alps of North-western Italy is unique in providing anchor points as stabilizing parts of the distal truncus cane below the glans by short and narrow lateral folds. To place this unusual species within the Nemastomatidae one must re-evaluate the usefulness of male genital morphological and other characters used in the systematics of the family. The resulting phylogenetic framework is supplemented with available molecular genetic data. Based on both datasets, the creation of a new genus seems justified. Saccarella schilleri gen. n. sp. n. is subsequently described and further defined. The endemism and biogeography of the harvestmen fauna in the South-western Alps are discussed with respect to this enigmatic genus.

Chemosystematics in the Opiliones (Arachnida): a comment on the evolutionary history of alkylphenols and benzoquinones in the scent gland secretions of Laniatores.

Large prosomal scent glands constitute a major synapomorphic character of the arachnid order Opiliones. These glands produce a variety of chemicals very specific to opilionid taxa of different taxonomic levels, and thus represent a model system to investigate the evolutionary traits in exocrine secretion chemistry across a phylogenetically old group of animals. The chemically best‐studied opilionid group is certainly Laniatores, and currently available chemical data allow first hypotheses linking the phylogeny of this group to the evolution of major chemical classes of secretion chemistry. Such hypotheses are essential to decide upon a best‐fitting explanation of the distribution of scent‐gland secretion compounds across extant laniatorean taxa, and hence represent a key toward a well‐founded opilionid chemosystematics.

Molecular phylogeny, biogeographic history, and evolution of cave-dwelling taxa in the European harvestman genus Ischyropsalis (Opiliones: Dyspnoi)

Abstract We estimated a multigenic molecular phylogeny and reconstructed biogeographic history for the European harvestman genus Ischyropsalis C.L. Koch 1839 (Dyspnoi). To reconstruct historical biogeographic patterns we conducted an algorithmic VIP analysis which revealed patterns consistent with a vicariance-dominated history. The existing morphology-based systematic framework for Ischyropsalis is mostly inconsistent with molecular phylogenetic results, and a new informal system is established that recognizes three main clades and several sub-clades. Species-level analyses revealed two non-monophyletic species (I. pyrenaea Simon 1872 and I. luteipes Simon 1872); subspecies of I. pyrenaea are distant relatives, and are formally elevated to species (I. pyrenaea pyrenaea to I. pyrenaea and I. pyrenaea alpinula to I. alpinula). A preference for cryophilic microhabitats has favored the diversification of high-altitude and cave-dwelling Ischyropsalis species; molecular phylogenetic data suggest that cave-dwelling species have evolved multiple times independently.