First record of the expansive harvestmen Dicranopalpus ramosus (Simon, 1909) (Arachnida: Opiliones) in Poland

The harvestmen Dicranopalpus ramosus (Simon, 1909) (Arachnida: Opiliones) is reported from Poland for the first time. It was found in the Dąbrówka near Poznań (Wielkopolska Lowland), more than 400 km East of the nearest known localities of this species in Germany.


INTRODUCTION
The genus Dicranopalpus Doleschal, 1852 is represented in Europe by two species: D. ramosus (Simon, 1909) and D. caudatus Dresco, 1948.For many years D. caudatus was considered a synonym of D ramosus (Staręga 1973, Martens 1978).Recently Wijnhoven and Prieto (2015) published the revalidation of taxonomical status of D. caudatus where the authors presented the accurate description of both species.According to them, D. caudatus is known from the Iberian Peninsula and two separate localities in southern England, while the range of D. ramosus extends from Morocco, northern coasts of Spain through France, England and Ireland, along the coastal zone of continental Europe reaching southern Sweden (Wijnhoven & Prieto 2015).
The natural area of the Dicranopalpus ramosus, originally covered probably only the northwestern periphery of the Mediterranean Sea and the southwestern part of the Atlantic coast, e.g.Morocco, northern Spain and southwestern France (Staręga 1973, Martens 1978, Hillard & Sankey 1989, Hillard 2005).Findings in Britain, however, supposedly are the result of the introduction of this species in 1950s from continental Europe (Hillard 2005, Hillard & Sankey 1989).
In the 90s of the 20th century there was a rapid expansion of the Dicranopalpus ramosus in Western Europe.Soon, this harvestmen was discovered in the Netherlands (Cuppen 1994), Ireland (Cawley 1995), Belgium (Slosse 1995), Germany (Schmidt 2004), western and central France (Delfosse 2004, Delfosse & Iorio 2009).Subsequent publications document the spreading of D. ramosus in the direction to north of Europe.Toft and Hansen (2011) report occurrence of this harvestman in Denmark, and Jonsson (2013) in southern Sweden (Fig. 1).Several publications indicate, that it became a very common species in a short period after its first record in Western Europe, what was documented in the reports from the Netherlands (Noordijk et. al. 2007, Wijnhoven 2009), Denmark (Toft & Hansen 2011), Luxemburg (Muster & Meyer 2014), Germany (Arachnologische Gesellschaft 2016) and Great Britain (Spider and Harvestman Recording Scheme 2016).Dicranopalpus ramosus is considered as an expansive species and according the current database of Arachnologische Gesellschaft (2016) the farthest east positions in Europe were distant by nearly 400 km from the western Polish border.
Therefore, the discovery of the population of the species in Dąbrówka near Poznań is now the easternmost locality of Dicranopalpus ramosus in Europe.

TAXONOMICAL IDENTIFICATION
Dicranopalpus ramosus is easy to identify.As the only species occurring in Western and Central Europe, it has long finger-like apophyses on the patella of the pedipalps present in both sexes (Figs 2g,h & 3).While resting, it takes a specific position, with all its legs spread sideways, unlike any other species of harvestman found in this part of the continent (Fig. 4).
Male (10 specimens): body ovoid, quite strongly flattened, length from 3.2 to 4.1 mm (3.7), covered with leathery cuticle (Fig. 2a).The color of the body variables, is a combination of different shades from yellow-brown to gray-brown in color.Cephalothoracic part lighter (yellowish-brown, dirty-yellowish, gray-yellowish) with a distinct darker (brown) lateral, trapezoidal or rectangular strip at the height of the eyes and darker areas of muscle insertions (Fig. 2a).Ocular tubercle unarmed, yellow-orange, away from the front edge approximately half of its length.Abdominal part gray-yellowish to gray-brown in color with a lighter stripe along the midline (Fig. 2a).Chelicerae honey in color, with numerous, darker tubercles tipped bristles on the dorsal surface of the basal segment and on the frontal surface of the second segment.Tips of pincers black-brown (Figs 2c, d).The length of the pedipalps approximately 4.4-5.1 mm (Fe Pe -1.3) yellow-brown to dark-brown in color (Figs 2g & 3), apical part of the foot distinctly darker.The femur of the pedipalp with short ventral process.Patella with long finger like apophysis on median side, reaching 2/3 of tibia length (Figs 2g & 3).The surface of the abdomen uniformly whitish.Coxa, genital operculum and abdominal sternites with quite a number of dark, short bristles.Coxa white to white-yellow, trochanters distinctly darker yellow-orange (brown-orange), other segments of the legs yellow-brown to brown, usually with slightly darker patella and lighter apical parts of femur and tibia.Tibia of all legs with pseudoarticulations, the number of which varies from 3 to 6 on Ti LI , LIII, LIV , and 4-9 on Ti LII .Often the number of pseudoarticulations on tibia of left and right side differs.Length of ♂ legs (Fe+Pa +Ti+Mt+Ta) (in parentheses length of femur): L I -28.2 (5.3); L II -51.0 (9.3); L III -27.6 (4.9); L IV -37.0 (6.5).The penis pale-yellow, slightly sclerotized, around 1.3-1.5 mm in length.Truncus of the penis rod like, in apical part with tear shaped cavity (Fig. 2i, j), the glans slightly darker, oval, stylus fixed and short, with a small tuft of bristles on the bottom side (Fig. 2j).
Female (6 specimens): body elongated, length 4.9-6.0mm (5.7) with distinct protuberance at the height of the 4-5 abdominal tergites (Figs 2b, m).Body coloration contrast, cephalothorax and first two tergites of the abdomen white-grayish other tergites distinctly darker (dark-gray).Along the midline of the abdomen extends brown framed, fingers like branched light spot (Fig. 2b).Ocular tubercle unarmed, yellow-orange, away from the front edge of the body approximately 2/3 of its length.Muscle insertions darker, as is darker spot behind ocular tubercle (Fig. 2b).The basic color of chelicera yellowish, with clear brown-black band on the II segment (Figs 2e, f) and black tips of the pincers.Tubercles on I and II segment of chelicera present, but in fewer number than in male.The length of the pedipalp 4.9 mm (Fe Pe -1.45).The femur of the pedipalp with short ventral process.Patella with long club like apophysis on median side, reaching almost to the end of the tibia (Fig. 2h).Trochanter and basal part of the femur whitish to white-yellow, apical part brownish, patella with the process dark brown, tibia light-brown with lighter apical part, foot gray-brown.Abdominal part of the body whitish, coxa slightly darker (yellow-whitish), trochanters yellow-orange.The femur and tibia white-yellowish or light-brown with distinctly darker ring in subapical part and with light (whitish) apical part.Patella distinctly darker than femur and tibia (brown), other segments of the legs yellow-brown.Tibia, alike the male with a variable number of pseudoarticulations: 3-7 on Ti LI , LIII, LIV , and 6-12 on Ti LII 1 .Length of ♀ legs (in parentheses length of femur): L I -24.5 (4.3); L II -42.2 (7.6); L III -23.4 (4.2); L IV -32.6 (5.6).Ovipositor length approximately 1.7-2.1 mm, width 0.30-0.40mm, light brown, with 22-27 segments.First 15-17 segments with a fairly long bristles, gradually declining toward the base.Receptaculum seminis small, fingers like (Fig. 2k), weakly sclerotized, located mostly in II and III full segment (Fig. 2l).

DISCUSSION
The newly discovered site in Poland is currently the most easterly known position of Dicranopalpus ramosus in Europe.The nearest noted locality of this harvestman are situated in central Germany (Lübeck -just about 440 km and Lehrte near Hanover (c.a.470 km) (Arachnologische Gesellschaft 2016, Fig. 1).The localization, where D. ramosus were found, is situated in a rapidly expanding suburban village belonging to the broader suburbs of Poznań.The harvestmen were collected and observed on a few hundred meter long wall surrounding a recently built residence, adjacent to the 19th-century park.Observations of many individuals over a period of several months suggest the existence of a sustainable population rather, than the effect of accidental introduction of a single individual, or a single deposit of eggs.However, this site of D. ramosus had to arise relatively recently, since searching for this species carried out in the immediate area and in several potential locations in western Poland gave a negative result.Presumably, the source of introduction of D. ramosus can be trees or ornamental plants brought from Western Europe, used to create a large garden.
In continental Europe Dicranopalpus ramosus is accounted for in mainly synanthropic environments, where it is found on the walls of buildings and on the trunks of trees, in parks, gardens, orchards, etc. (Hillard 2005, Noordijk et al. 2007, Wijnhoven 2009, Muster & Mayer 2014).It was also noted from ruderal environments, semi-natural forests, etc. (Muster & Mayer 2014).Data from the UK (Spider and Harvestman Recording Scheme 2016) point to the trunks, branches and leaves of trees and shrubs in natural environments as the main environment of occurrence of D. ramosus, and less likely, the data indicate the walls.It is possible that the advantage of synanthropic posts in continental Europe stems from the fact that these large, often resting in exposed places harvestmen are just easily noticeable there, in opposition to the individuals sitting on the trunks of trees, etc.The possibility of such a "methodical error" is mentioned by Noordijk et al. (2007).The second cause of the differences in the Dicranopalpus ramosus environmental preferences between Great Britain and continental Europe may be another phase of expansion.In Great Britain D. ramosus is present since 1950s of the 20th century, so it is now a long-established species and widely distributed (Spider and Harvestman Recording Scheme 2016).In the Benelux countries (Wijnhoven 2009, Muster & Meyer 2014), Germany (Arachnologische Gesellschaft 2016), Denmark (Toft & Hansen 2011), and Sweden (Jonsson 2013), D. ramosus is a relatively newcomer, therefore, its presence is limited mainly to anthropogenic environments, from where it is just starting to colonize the natural biotopes.The colonization scheme confirms the observations of the spread of other invasive harvestman species in Poland, e.g.Opilio canestrinii (Thorell) (Rozwałka & Staręga 2012) or Odiellus spinosus (Rozwałka et al. 2013(Rozwałka et al. , 2014)).

Fig. 1 .
Fig. 1.Distribution of Dicranopalpus ramosus in Europe: asterisk -newly found position, dots -known data from the nearest location only, shaded area -likely continuous range.