Platycampus luridiventris ( Fallen , 1808)

Prous, Marko, Liston, Andrew, Kramp, Katja, Savina, Henri, Vardal, Hege & Taeger, Andreas, 2019, The West Palaearctic genera of Nematinae (Hymenoptera, Tenthredinidae), ZooKeys 875, pp. 63-127 : 63

Platycampus luridiventris ( Fallen, 1808)

Tenthredo alnicola Bechstein & Scharfenberg, 1805: 867. Syntypes, larvae, lost. Type locality: Germany. Synonymy with Leptopus luridiventris by Brischke (1883b: 216). Nomen oblitum after Blank et al. (2009: 47).

Tenthredo luridiventris Fallén, 1808: 115-116. Syntype(s) ♀, not examined (revised by Lindqvist 1956: 9), in MZLU. Type locality: Sweden. Nomen protectum after Blank et al. (2009: 47).

Nematus hypogastricus Hartig, 1837: 184. Syntypes ♀, Deutschland, lectotype ♀ here designated, (GBIF-GISHym3464, images: https://doi.org/10.6084/m9.figshare.4788550), in ZSM. Type locality: Germany. Paralectotype ♀ (GBIF-GISHym3465), in ZSM. Listed in synonymy with Leptopus luridiventris by Thomson (1871: 78).

Nematus alnivorus Hartig, 1840: 27. Syntypes ♀, Norddeutschland, lectotype ♀ here designated (GBIF-GISHym4675) in NFVG. Type locality: Harz, Roßtrappe (Germany). Paralectotype 1♀, in FMNH. Synonymy by Lindqvist (1965: 31-32).

Nematus rufipes Tischbein, 1846: 77. Syntypes ♂♀(?), lost. Type locality: Eutin (Germany). Listed in synonymy with Leptopus luridiventris by Konow (1905: 78).

Leptopus rufipes Förster, 1854: 276-277. Syntypes ♂, Aachen, lectotype ♂ here designated, (GBIF-GISHym3468, images: https://doi.org/10.6084/m9.figshare.4788580), in ZSM. Type locality: Aachen (Germany). Paratype ♂ (GBIF-GISHym3469), in ZSM. Synonymy with Leptopus luridiventris by Brischke (1883b: 216).

Nematus protensus Förster, 1854: 322-323. Syntype(s) ♀, Aachen, lectotype ♀ here designated, (GBIF-GISHym3467, images: https://doi.org/10.6084/m9.figshare.4788595), in ZSM. Type locality: Aachen (Germany).

Camponiscus Healaei [sic!] Newman, 1869: 215-217. Syntypes ♂♀, larvae, lost. Type locality: United Kingdom. Synonymy with Tenthredo luridiventris by Cameron (1873: 84).

Nematus Tischbeini [sic!] André, 1880: 120. Replacement name for Nematus rufipes Tischbein, 1846.

Nematus Fennicus [sic!] André, 1880: 133. Syntype(s) ♀, deposition unknown. Type locality: Finland. Synonymy by Forsius (1920: 111).

Nematus alnicola Zaddach in Brischke, 1883b: 188-189. Holotype ♀, "wohl im westlichen Deutschland", lost. Type locality: Germany(?). Synonymy with Leptopus luridiventris by Brischke (1883b: 216). Secondary homonym of Tenthredo alnicola Bechstein & Scharfenberg, 1805.

Nematus cellularis Brischke, 1884: 138-139. Syntypes ♂♀, Danzig, lost. Type locality: Gdansk (Poland). Primary homonym of Nematus cellularis Dahlbom, 1836. Synonymy with Leptocercus luridiventris by Konow (1901: 89).

Platycampus luridiventris var. pleuritica Enslin, 1915: 322. Syntype(s) ♀, no data, lectotype ♀ here designated (GBIF-GISHym3466, images: https://doi.org/10.6084/m9.figshare.4788727) in ZSM. Type locality: Lisieux (France).

Taxonomy.

W. Heitland, H. Pschorn-Walcher and J. Herbst studied European populations of P. luridiventris feeding on Alnus glutinosa , incana , and viridis . They found the populations on each host to be genetically segregated ( Herbst and Heitland 1994), and that the different hosts correlated with differences in behaviour ( Heitland and Pschorn-Walcher 2005), and partly in the morphology of larvae ( Heitland and Pschorn-Walcher 1992): setae on the head and body of larvae from glutinosa tended to be shorter than of those from incana , but setae of larvae from viridis usually did not differ from those on glutinosa . Our genetic data based on sequences of four genes contradicts, at least partly, the results of Herbst and Heitland (1994). Although six sequenced larvae collected in three different localities (Lower Austria) from three different Alnus species do segregate based on mitochondrial COI (1078 bp) into three clusters according to the host plant and locality (maximum distance 2.2%), the nuclear sequences (NaK, POL2, TPI: 5017 bp including introns) are practically identical (only four variable / heterozygous positions, giving a maximal pairwise distance of 0.08%), so that the tree structure for P. luridiventris on Fig. 1 is entirely determined by COI. For comparison, nuclear divergence within most other species of Nematinae (based on heterozygous females) is larger, on average 0.2% or up to 1%. In addition, COI sequences of two specimens reared from A. incana from Abisko (DEI-GISHym21133, DEI-GISHym21134) are identical to two larvae collected from A. glutinosa from Lower Austria (DEI-GISHym21496, DEI-GISHym21497). Since different food plant species can affect gene expression differently in feeding larvae ( Yu et al. 2016, Orsucci et al. 2018, Okamura et al. 2019), one can speculate that the allozyme analyses by Herbst and Heitland (1994) were influenced more by differences in the expression of the studied proteins (preferential expression of certain alleles or isoforms) than differences in genetics. Morphologically, we noticed conspicuous differences in the overall shape and spacing of the sawteeth, particularly the apical ones, between the reared Swedish specimens ( Figs 128-129 ) and a German specimen belonging to the other barcoding cluster ( Fig. 132 ). However, examination of further specimens revealed wide variability in the shape and spacing of the sawteeth, with several intermediates (e.g., Figs 130-131 ), so that finally no clear morphological separation of two groups seemed possible. Perhaps this variability is mainly correlated with geographical occurrence, with a tendency in northern specimens to shorter, more projecting teeth: the lancets of two Abisko specimens ( Figs 128-129 ) have the most clearly projecting and shortest sawteeth (with correspondingly long distances between them), while a specimen from southern Sweden ( Småland) has long and flat teeth (more closely spaced) ( Fig. 131 ), and a specimen from Central Sweden is intermediate with regard to the shape of the teeth, although they are widely spaced ( Fig. 130 ). In these examples, the differences are not caused by wear of the saw teeth, because the outlines of the teeth are angular and the denticles are clearly differentiated. A highly worn lancet has rounded edges of the teeth, and the denticles are no longer clearly discernible ( Fig. 133 ). Note that apparent differences in the overall curvature of the illustrated lancets are the result of preparation: each annulus of the lamnium can move slightly, relative to its neighbours, and slight differences in the curvature of the whole lamnium are thus mostly artefacts resulting from preparation. In the light of the foregoing considerations, we conclude that although the three segregates could perhaps be considered to be host plant races ["foodplant races"], as already suggested by Heitland and Pschorn-Walcher (2005), they should certainly not be accorded a formal nomenclatural status.

Description.

Body length: female 5.0-7.0 mm, male 4.5-6.0 mm. Female: head black except for palps, and more or less labrum, underside of antennal flagellum, and sometimes more or less scape and pedicel. Thorax black, except for yellow tegula and more or less posteriodorsal edges of pronotum. Sometimes lateral edges of median mesoscutal lobe, and upper mesepisternum pale. Legs pale (orange), with dark metatarsus and apex of metatibia, and more or less dark bases of coxae. Wing venation mostly brown, with centre of fore wing stigma paler. Cerci pale; rest of abdomen from completely black except for obscurely brown area of hypopygium, to all sterna bright yellow, sometimes also with yellow on downturned lateral edges of terga. One reared female from Abisko has dorsal parts of terga 2-4 pale. Variability in the shape of the teeth of the lancet is considerable ( Figs 128-133 ): see also under Taxonomy above. Male: colour similar to female, but pronotum entirely black. Sternum 9 black to pale. Harpes more or less pale.

Similar species.

If the nearly complete loop formed by the curved up base of fore wing vein 2A+3A in Platycampus is overlooked, then it might be mistaken for Stauronematus platycerus , which is similarly coloured and also has bifid claws (but with an additional basal lobe not found in Platycampus ), or perhaps a Pristiphora species.

Life history.

Host plants: Alnus glutinosa , incana , and viridis ( Heitland and Pschorn-Walcher 1992). Mentions by Lorenz and Kraus (1957) of Betula , Corylus avellana and Rubus as hosts of luridiventris are likely to have been based on misidentifications ( Zinovjev 1986, Heitland and Pschorn-Walcher 1992). A strictly univoltine species, although some populations exhibit polymodal emergence patterns. Correlated with its highly distinctive larval morphology ( Figs 72-73 ) compared to other nematine genera ( Boevé and Angeli 2010), Platycampus luridiventris has many peculiar behavioural traits, such as the extremely long time, of approximately three months, taken by the larva to mature ( Heitland and Pschorn-Walcher 2005). Oviposition is into the leaf petiole or midrib, with a maximum of three eggs per leaf. The larva is crepuscular according to Heitland and Pschorn-Walcher (2005), and feeds only for very short periods, making holes in the leaf blade, and during the day is normally found immobile on the leaf underside, often in an angle between the midrib and a lateral vein. Sex ratio appears to be normal for netted specimens, i.e., males about as abundant as females, but is heavily skewed towards males in material collected with Malaise traps.

Distribution.

Widespread in Europe, from the British Isles to the Balkans, and north to Norway and Finland ( Taeger et al. 2006). Earlier published records of luridiventris from the East Palaearctic and Oriental Realms, such as by Benson (1963) from Sichuan, China, probably often refer to other species ( Zinovjev 1986). For Russia, Sundukov (2017) lists only European areas and the Ural as definite areas of occurrence.

Occurrence in Sweden.

Published records: Thomson (1871) wrote "not rare, throughout Sweden". Material examined from Skåne, Småland, Östergötland, Västergötland, Bohuslän, Södermanland, Uppland, Norrbotten, Torne Lappmark.

Specimens examined.

Estonia: 3♀, 1♂ (SDEI, TUZ). Finland: 1♂ (SDEI). France: 1♀, 1♂ (SDEI). Germany: over 100♀ and 150♂ (SDEI, ZMHB, ZSM), including 1♀ (DEI-GISHym11313), Mecklenburg-Vorpommern, Wrangelsburg 16 km SE Greifswald, 54.01611N, 13.59972E, 07.05.2011, leg. H.-J. Jacobs (SDEI); 1♀ (DEI-GISHym31936), Mecklenburg-Vorpommern, Ventschow, 53.78000N, 11.57000E, 09.06.2012, leg. H.-J. Jacobs (SDEI). Poland: 1♀ (SDEI). Sweden: Skåne: 1♂, Simrishamns kommun, Stenshuvuds nationalpark, Stenshuvud-Krivarboden, 55.66035N, 14.27561E, 06-20.08.2004, leg. SMTP (NHRS). 1 specimen, Bökeberg (NHRS). Småland: 1♀ (DEI-GISHym31938), 1♂ (DEI-GISHym31112), Hultsfred, Kloster Gård, 100 m, 57.49700N, 15.87100E, 31.05.2013, leg. Liston, Prous & Taeger (SDEI). 9♀, 2♂, Nybro kommun, Bäckebo, Grytsjöns naturreservat, 56.93148N, 16.08550E, 18.05.-16.06.2006, leg. SMTP (NHRS). 9 specimens (NHRS). Östergötland: 1♂, Ödeshögs kommun, Omberg, Storpissan, 58.33500N, 14.65521E, 28.05-05.07.2005, leg. SMTP (NHRS). Västergotland: 1 specimen (NHRS). 4 specimens (NHRS). Bohuslän: 1 specimen (NHRS). Södermanland: 1 specimen (NHRS). Uppland: 1 specimen (NHRS). Ångermanland: 1♀ (DEI-GISHym31937), Ramvik, 62.87200N, 17.85800E, 04.06.2013, leg. Liston, Prous & Taeger (SDEI). Norrbotten: 1♂ (DEI-GISHym20975), Pajala 8 km NE, 150 m, 67.25200N, 23.54800E, 10.06.2014, leg. E. Heibo (SDEI). Torne Lappmark: 2♀ (DEI-GISHym21133, 21134), Abisko 9 km E (Stordalen), 400 m, 68.35000N, 19.03500E, larvae 26.08.2013, Alnus incana kolaensis, emerged 04.2014, leg. Liston (SDEI). Switzerland: 2♂ (SDEI, ZSM). United Kingdom: 1♀ (SDEI).

Figures

Figure 1. Maximum likelihood tree of Nematinae based on four genes (COI, NaK, POL 2, TPI). Only specimens sequenced for all four genes were included. Short introns from POL 2 and TPI were excluded. The best-fit model chosen according to Bayesian information criterion was GTR + R 4. Numbers at branches show SH-aLRT support (%) / ultrafast bootstrap support (%) values. Support values for weakly supported branches (<90) are not shown. Letters " f " and " m " stand for " female " and " male ", and are not given for larvae. Numbers at the end of the tip labels refer to the length of the sequence and the number of ambiguous positions (e. g., heterozygosities). The number of ambiguous positions given for two males are due to variation in mitochondrial COI because of possible heteroplasmy. The tree was rooted as in Prous et al. (2014). The scale bar shows the number of estimated substitutions per nucleotide position.

Figures 128 - 133. Playcampus luridiventris, lancets, variability and wear of teeth 128 DEI-GISHym 21133, Sweden, Torne Lappmark 129 DEI-GISHym 21134, Sweden, Torne Lappmark 130 DEI-GISHym 31937, Sweden, Angermanland 131 DEI-GISHym 31938, Sweden, Smaland 132 DEI-GISHym 11313, Germany, Mecklenburg-Vorpommern 133 DEI-GISHym 31936, Germany, Mecklenburg-Vorpommern, teeth worn.

Figures 69 - 76. Larvae of Nematinae 69 Mesoneura opaca 70 - 71 Pseudodineura clematidis; ventral, dorsal 72 - 73 Platycampus luridiventris 74 Pristiphora malaisei from Dryas octopetala 75 Cladius compressicornis 76 Cladius pectinicornis.