Perapion connexum (Schilsky, 1902) (Coleoptera, Apionidae) in Central Europe, a case of plant expansion chase

Abstract Perapion connexum (Schilsky) is recorded for the first time from Hungary and Kyrgyzstan, and new distribution data from Ukraine and Russia are provided. Preliminary placements of this weevil in faunal checklists for Poland and Slovakia are here documented with detailed data. Its occurrence in Austria based on older evidence, is discussed. The neophytic and invasive in Central Europe sorrel Rumex confertus Willd. is confirmed to be its unique host plant in Poland. Morphology of the newcoming weevil is described and illustrated, and the key to all Central European species of Perapion is presented.


Introduction
The title weevil species was originally described from Aulie-Ata (currently Taraz) in SE Kazakhstan and long considered as confined to Asian fauna (Schilsky 1902, Wagner 1930. After the World War II it was found on several distant localities in the European part of Russia, both in the extreme south (vicinity of Krasnodar) and well north of the 50 th parallel of north latitude (Bryansk, Ul'yanovsk), as well as in Eastern Ukraine (Luhansk and Kharkiv regions) and in Moldova (Korotyaev 1987, Poiras 1998). Further spines. It strongly resembles Aizobius sedi in the colour of integument, but the latter species has different frons sculpture, with well defined punctures and long median fovea, pronotum distinctly rounded at sides, and a ventrally spined basal segment on all male tarsi. See the key to species of Perapion occurring in Central Europe given below.
Morphology. Body length 2.0-2.3 mm. Integument and vestiture. clearly black with slight "oily" glint ( Fig. 1). Body covered with sparse and extremely fine white-semitransparent hair-like scales, on pronotum as long as diameter of the largest punctures, on elytral disc not longer than half interval's width and unordered on intervals, not aggregated in any part of elytra, slightly denser on mesothoracic epimera and anepisterna, along metanepisterna condensed to form a thin white line. Entire body surface with dense microreticulation, scale-like and rough on head and the basal half of rostrum.
Rostrum in dorsal view subcylindrical with obtuse widening at antennal insertion, obscuredly punctured throughout, except distal third completely mat.
Head narrow, subconical, nearly as long as wide, about 1.5× narrower than pronotum (Figs 7,8); eyes gently convex; frons slightly depressed in middle, with a few indictinct strigae partly obscured by dense microsculpture; puncturation on vertex lacking or indefinite, rarely with few punctures much smaller than on pronotal disc; head ventrally between eyes evenly scale-like microsculptured, without irregular asperities.
Pronotum small, slightly shorter than wide, with weakly rounded sides, at base 1.1-1.2× as wide as at apex, coarsely punctured, the punctures usually of 3-4 combined ommatidia size, with flat, heavily and somewhat roughly microreticulate interspaces; prescutellar fovea not wider than single puncture, as long as 3-4 neighbouring punctures combined.
Wing without radial window.
Ventrites. Metaventrite and abdominal ventrites I, II microreticulate and evently punctate, shiny, the punctures much smaller than on pronotal disc, well over a diameter apart from each other; abdominal ventrites III-V with strong, scale-like microsculpture.
Male. Rostrum slightly shorter than pronotum, 2.20-2.35× longer than wide, in profile almost straight and somewhat wedge-like, distinctly narrowing apicad in distal half (Fig. 11). Antennal insertion at basal 0.38-0.42 of rostrum. Abdominal ventrite V very broadly rounded apically. Metatarsus unarmed. Pygidium half exposed, with very broad complete transverse sulcus. Terminalia only slightly different from those of P. curtirostre, mainly in more elongate tegminal plate and aedeagus. Sternite VIII broad, with very short and indistinct lobes. Sternite IX with slightly asymmetrical fork half as long as apodeme. Tegmen with phallobase as long as apodeme; tegminal plate fused, short, devoid of macrochaetae, with broadly and very deeply emarginate prostegium. Aedeagus short and flattened, with pedon about 4.5× as long as wide, membranous tectum and free apophyses less than 0.2× as long as pedon; endophallus finely and more or less evenly microspinose.
Material examined.   (Schilsky) in Central Europe mentioned in the text (circles -new records; black square -record by Gosik (2006) in Gródek nr. Hrubieszów, Poland; black triangle -record by Mazur and Kuśka (1994)  Biology. Korotyaev (1987) collected this weevil from broad-leaved sorrel species. The senior author (MW) collected it in Ukraine by general sweeping of wet meadows in the Dniester valley, where an unidentified broad-leaved sorrel was abundant. Poiras (1998) identified the host plant as Rumex confertus Willd. and, indeed, in Poland the weevil was collected exclusively from this sorrel species. In the Udmurt Republic Dedyukhin (2009) confirms the same host plant, but he collected adults also from the sorrels resembling Rumex crispus L. The life cycle of P. connexum remains unknown, but the adults were in Poland mostly beaten in summer from mature infruitescences, which may indicate larval feeding on developing seeds or eventually in fruit petioles, rather than in thick main stem or leaf petioles. In Poland teneral beetles were observed since mid-July.
Comments. Korotyaev (1987) reported a specimen from the collection of ZIN labelled "Austria", which was then approximately 800 km distant from the westernmost known locality in Moldova. This outstanding record was ignored by the authors of subsequent Centraleuropean weevil catalogues (Lucht 1987, Böhme 2005, Alonso-Zarazaga 2011), but in the light of our current findings and proximity of current Slovak and Hungarian localities, this opinion should be verified and the occurrence of P. connexum in Austria should be considered as likely, though obviously requiring confirmation with new data. Unfortunately, the information on distribution of its host plant in Austria is poor and equivocal. It was missing from the first two editions of Austrian Excursionsflora by Fritsch (1897Fritsch ( , 1909, but it was noticed from Austria since at least mid-20 th c. (Tutin et al. 1964). Then Jalas and Suominen (1979) did not justify Austrian records of this sorrel, and they were consequently removed from the revised editions of Flora Europaea. Most recently the occurrence of R. confertus in Austria has been confirmed in the departments of Wien, Niederösterreich, Steiermark and Kärnten (Fischer et al. 2008), but the history of its invasion(s) remains unclear.
The occurrence of P. connexum in Poland, as based on the abovementioned data, was earlier generally announced by Wanat and Mokrzycki (2005), and further confirmed by Gosik (2006). Analogously, the weevil has been just placed on the list in Slovakia (Benedikt et al. 2010). The range of this weevil in Poland seems still strictly limited to the southern section of the Bug River Valley, which constitutes there the country border between Poland and Ukraine, but one of the listed localities (Kosyń) is situated ca. 18 km "inland" West of the river. Along the Bug River Valley the southernmost site is Gródek near Hrubieszów (Gosik 2006 (Korotyaev 1987) and even 57°N in the Udmurt Republic (Dedyukhin 2009) and the northernmost Siberian sites (Legalov 2002), despite of continental climate. Thus the Lower Bug Valley seems to be the most obvious natural area for further spreading of P. connexum in Poland and presently limited range of the weevil there may indicate a stage of current invasion.
Rumex confertus is an invasive plant in Europe, and its natural range ends probably close to Southeastern Poland, in Southern Slovakia and Hungary (Rechinger and Schreiber 1957, Tutin et al. 1964, Jalas and Suominen 1979, Dostál 1989, Jehlík et al. 2001). However, although it is known from the Bug River Valley in Poland since 1873 (Eichler and Łapczyński 1892), its autochtonous status in Poland is doubtful. According to Trzcińska-Tacik (1963) andTacik (1992), who studied distribution of this sorrel species in most detail, its natural range North of the Carpathians rather ends in Western Ukraine. Its spreading to the West of Poland started probably since 1950 (Tokarska-Guzik 2005) and currently it appears a common plant in Poland east of the Vistula river, reaching even the Baltic coast to the North, and it has many diffused localities also in the Western Poland (Trzcińska-Tacik 1963, Zając and Zając 2001, Stosik 2006. It extends its range widely also to the North, being probably introduced to Skandinavia with the Soviet army transports since the very early 20 th century in Finland, and about mid 20 th century in Norway and Sweden (Snogerup 2000). It is now widespread also in Baltic countries and treated as invasive plant in Lithuania (Gudžinskas 1999). The Southern stream of its invasion to Central Europe seems less active. The plant is still very rare in Czech Rep. with just a few isolated and ephemeral localities (Jehlík et al. 2001) and, as stated above, it has quite similar status in Austria.
Following current distribution of the host plant, further expansion of P. connexum in Central Europe from the sites showed in Fig. 12 seems very likely especially through the territory of Poland, and it could be monitored quite easily by summer sweeping of mature inflorescences of R. confertus. The same method should be applied on stabilized localities of Rumex confertus in Austria to record its occurrence and expansion.

Key to Central European species of Perapion † :
The key includes also Aizobius sedi (Germar, 1818), a related and morphologically similar species.