Leiobunum C.L. Koch, 1839

Martens, Jochen & Schönhofer, Axel L., 2016, The Leiobunum rupestre species group: resolving the taxonomy of four widespread European taxa (Opiliones: Sclerosomatidae), European Journal of Taxonomy 216 (216), pp. 1-35 : 3-5

Genus Leiobunum C.L. Koch, 1839

Type species

Designation by Thorell, 1876: Opilio fasciatus Herbst, 1798 = Leiobunum rotundum (Latreille, 1798) .

Remark

Of the representative material investigated, we found the four hypothesized species well separable upon a number of somatic and male genital morphological characters, which are summarized in Table 1 for convenient use. Species appear largely allopatric, except for L. subalpinum , which is firmly nested within the area of L. rupestre . In addition, parapatric and locally sympatric occurrences of two species under discussion in East-Central Europe cannot be excluded, especially in South Poland, the central Alps and close to the Czech/Slovak border area ( Fig. 2 ).

Leiobunum subalpinum Komposch, 1998 is considered most closely related to L. rupestre ( Komposch 1998) and, as such, is also regarded as a member of the L. rupestre species group. As it is easily discriminated from all discussed forms by its dark coxal markings and, apart from L. rupestre , by its restricted alpine range, it is not featured here (see Komposch 1998; Komposch & Gruber 2004 for

details) except for general remarks; its geographic range is indicated in Fig. 2 . In addition, the poorly known Leiobunum nigripalpe Simon, 1889 , described from the western Alps ( France), was reinvestigated. However, the type series represents a composite collection of at least two different small Nelima Roewer species, both unaffiliated to the L. rupestre species group. This holds true, too, for the specimen depicted as Leiobunum nigripalpe in Martens (1978) , representing a yet to be identified Leiobunum species.

Figures

Fig. 2. Distribution of the species of the Leiobunum rupestre species group. Red squares = L. rupestre Herbst, 1799; blue circles = L. gracile Thorell, 1876; green triangles = L. apenninicum (Martens, 1969); stippled line circumscribes area of L. subalpinum Komposch, 1998. Type localities are indicated by abbreviated taxon names (ape = apenninicum; gla = glabrum; gra = gracile; lae = laeve; nor = norvegicum; rup = rupestre; sub subalpinum; tis = tisciae). Arrows indicate a specified locality, if unprecisely given, the general area is indicated (rupestre = Saxony; gracile, laeve = Scania).

Tables

Table 1. Comparison of somatic characters of Leiobunum apenninicum (Martens, 1969), L. gracile Thorell, 1876 and L. rupestre Herbst, 1799. L. subalpinum Komposch, 1998 is not included, because it is very similar to L. rupestre and is easily identified by its black coxal markings. For comparison with L. rupestre we refer to Komposch (1998). If not otherwise mentioned, characters apply to males only. Characters outlining a single species are given in bold, more variable characters are given in italics. The combination of several characters for determination is advised. Palpal spination is variable, apparently the appearance in ordered rows is an individual character. Body coloration varies with age and population, aged specimens are darkest.

L. rupestre Herbst, 1799	L. gracile Thorell, 1876	L. apenninicum ( Martens, 1969)
in both sexes dorsum smooth, granulation cannot be distinguished with 250×, with a few pointed granules present	in both sexes dorsal granulation consisting of flat, pointed granules, regularly spaced, well visible at 250×	in both sexes dorsal granulation consisting of flat, pointed granules, regularly spaced, well visible at 250×
palp-femur with irregular rows of medium-sized triangular spines on ventral side; dorsal side few on distal part, ventral spines more slender, many pointing downward	palp-femur with irregular rows of large triangular spines on ventral side; dorsal side few on distal part, ventral spines broader, not so slender	palp-femur with few spines, normally restricted to ventrodistal, rarely few large spines on ventral side, only single spines on dorso-distal side
palp-tibia slightly concave in lateral view at ventro-distal end, therefore forming a flat S-bend	palp-tibia slightly concave at ventro-distal end, therefore forming a flat S-bend	palp-tibia not concave at ventro-distal end, therefore forming a flat C-bend
palp-patella appears longer and less massive	palp-patella appears longer and less massive	palp-patella appears shorter and more massive
palp-tarsus bent over its whole length	palp-tarsus mostly straight, bent only in distal third	palp-tarsus bent over its whole length
denticles and hairs on ventral side of palp-tibia darker and therefore well visible	spines and hairs on ventral side of palp-tibia lighter and therefore hard to be seen	spines and hairs on ventral side of palp-tibia lighter and therefore hard to be seen
eye mound in both sexes always without spines	eye mound in both sexes without spines, sometimes one spine present	eye mound in both sexes with 1–3 small spines on each side, rarely absent
in both sexes dorsal coloration without pair of white spots on each area along the median line	in both sexes dorsal coloration with small white spots on each area along the median line	in both sexes dorsal coloration with pair of white spots on each area along the median line
in females no lateral coloration of opisthosoma with a blurred parallel pattern of zigzag lines	in females lateral coloration of opisthosoma with a blurred parallel pattern of zigzag lines, best seen at low magnification	in females lateral coloration of opisthosoma with a blurred parallel pattern of zigzag lines, best seen at low magnification