Plateumaris C. G. Thomson, 1859

Geiser, Elisabeth, 2023, Revision of the Palaearctic species of the genus Plateumaris C. G. Thomson, 1859 (Coleoptera, Chrysomelidae, Donaciinae), ZooKeys 1177, pp. 167-233 : 167

Genus Plateumaris C. G. Thomson, 1859

Plateumaris C. G. Thomson, 1859: 154.

Euplateumaris Iablokoff-Khnzorian, 1966: 121.

Juliusina Reitter, 1920: 41.

Type species and localities.

Plateumaris C. G. Thomson, 1859: Donacia nigra Fabricius, 1792: Germania.

= Prionus bracatus Scopoli, 1772: Carniola [now Slovenia].

Euplateumaris Iablokoff-Khnzorian, 1966: Leptura sericea Linnaeus, 1758: Europe.

Juliusina Reitter, 1920: Prionus bracatus Scopoli, 1772: Carniola [now Slovenia].

Timeline of taxonomic history and synonymies.

1758: Linnaeus described the genus Leptura with 22 species. Two of these species belong to the (later established) Donaciinae : Donacia aquatica and Plateumaris sericea ( Geiser and Geiser 2023). Linnaeus established only the taxonomic categories: classis - Coleoptera - genus - species, e.g.: Insecta - Coleoptera - Leptura - Plateumaris sericea .

1760: Linnaeus mentioned Leptura sericea in his 'Fauna Suecica’ with the same diagnosis as in Linnaeus (1758) but with more details. Therefore, the species is sometimes cited as Leptura sericea Linnaeus, 1760 (e.g., in Silfverberg 2010), but the first description date is clearly Linnaeus, 1758 (see Geiser and Geiser 2023 for original Latin text of Linnaeus and translation).

1762: Geoffroy erected the genus Prionus for the species Cerambyx coriarius Linnaeus, 1758. It now belongs to the Cerambycidae as does the genus Leptura .

1772: Scopoli described Prionus bracata .

1775: The genus name Donacia was erected by Fabricius. He described Donacia crassipes and Donacia simplex and assigned Leptura aquatica L., 1758 to the genus Donacia , but he did not change the genus name of Leptura sericea L., 1758. Other Plateumaris species were described as Leptura , e.g., Leptura consimilis Schrank, 1781. It is remarkable that these early entomologists had already assigned them to a genus other than Donacia .

1796: The category “Chrysomelidae” was established between order and genus for insects by Latreille.

1802: Latreille established the coleopteran family Chrysomelidae .

1837: Kirby established the subfamily Donaciinae .

1859: The genus name Plateumaris was erected by C. G. Thomson (translation in Geiser and Geiser 2023), but some authors, especially Americans, preferred Donacia as the genus name in their new descriptions. Even Marx (1957) regarded Plateumaris as a subgenus of Donacia . The Palaearctic Plateumaris weisei (Duvivier, 1885) and P. constricticollis (Jacoby, 1885) were also originally described as Donacia .

1920: Reitter split the Palaearctic Plateumaris into two subgenera: Plateumaris sensu stricto and Juliusina . He assigned P. sericea and P. discolor to Plateumaris s. str. and he described P. annularis in a footnote to P. sericea . In the same footnote he assigned P. obsoleta to P. annularis , but not as a synonym, and he placed P. amurensis near to P. discolor . The subgenus Plateumaris Juliusina contained P. bracata , P. consimilis , P. rustica , and P. affinis . To the latter species he assigned P. sulcifrons and P. mongolica . Moreover, Reitter made no designation of type specimens to either of the new subgenera.

Type species designations.

Thomson (1859) stated "Typus P. nigra (FAB.) [= Fabricius]" in the original description of the genus Plateumaris , but most authors cited "Thomson, 1866" as the year of the original description. Thomson (1866) is an extensive book but contains no type designation because this had been done previously in 1859. Therefore, the prevailing opinion was that there existed no type designation for the genus Plateumaris (which was wrong) and nor for the subgenera Juliusina and Plateumaris s. str (which is true). Subsequently, Chen (1941) designated Donacia affinis Kunze as the type species for Plateumaris , but this was overlooked by Monrós (1959) who designated Donacia geniculata Thomson (= Donacia discolor Panzer) as the type species for Plateumaris s. str. and Prionus bracatus Scopoli for Juliusina Reitter.

Iablokoff-Khnzorian (1966) suggested the name Euplateumaris for the subgenus Euplateumaris Plateumaris s. str. established by Reitter, with Donacia sericea (L.) as type species. He also re-established D. nigra F. (= Plateumaris bracata ) as type species of the genus Plateumaris , apparently unaware of both designations by Monrós (1959) and Chen (1941), and therefore placed Juliusina as a junior synonym of Plateumaris because both were named based on the same nominal taxon. Jolivet (1970) followed the designation of Iablokoff-Khnzorian (1966) but Mann and Crowson (1983) accepted Monrós’ designations and advocated acceptance of Plateumaris s. str (= Euplateumaris ) and Plateumaris (Juliusina) as the correct subgeneric classifications of Plateumaris . Lopatin (1984) correctly cited P. bracata as type species of Plateumaris but he assigned this species to Plateumaris (Juliusina) . The same, clearly incorrect, arrangement was used by Lopatin and Kulenova (1986) when assigning P. sericea to Plateumaris (Plateumaris) .

The names Plateumaris Thomson, 1859 and Juliusina Reitter, 1920 are based on the same type species ( Prionus bracatus ) which makes the subgenus Plateumaris Juliusina a synonym of Plateumaris in the sense of the whole genus, which was endorsed by Warchałowski (2010). This synopsis of the type species designations and the use of the names as described was elaborated in detail by Askevold (1991). Also, he was the first who attempted to assess the validity of Plateumaris as a genus and the validity of the two subgenera.

Taxonomic status of Plateumaris .

Most European authors accepted the genus Plateumaris , but North American authors were reluctant and oscillated between the use of this name at generic and subgeneric ranks within the genus Donacia . This ambiguity led to confusion about the genus name Plateumaris , worsening the existing confusion over the name Plateumaris of the Palaearctic species (see above).

Askevold (1990) understood that Plateumaris was monophyletic, defined by the synapomorphy of the ovipositor structure, and that Plateumaris was the sister group to all other Donaciinae , and his morphologically based conclusions were confirmed by several independent molecular analyses ( Sota and Hayashi 2007; Kölsch and Pedersen 2008; Sota et al. 2008; Hayashi and Sota 2014; Reis et al. 2020).

Previous subgeneric classifications.

Askevold (1990, 1991) concluded that the division into two subgenera by Reitter (1920) did not reflect the phylogenetic reality. The two subgenera were erected based on characters that do not occur in all members assigned to them or they were based on plesiomorphic characters. Notably, neither subgenus can be characterised by a synapomorphy. His conclusion that Euplateumaris and Juliusina cannot be regarded as subgenera has also been confirmed by molecular studies ( Kölsch and Pedersen 2008; Sota et al. 2008). Therefore, this paper does not deal with the confusion over subgeneric names and various designated type species.

In central Europe, the widely used key of Mohr (1966a) separated Plateumaris into two subgenera. The short note in the updated key by Kippenberg (1994: 22), "The separation into the subgenera Juliusina Rtt. and Plateumaris s. str. is not tenable," did not prevent coleopterologists from using the subgeneric names in their collections or publications, and even on a Palaearctic scale, the subgeneric names Euplateumaris and Juliusina were still used by Silfverberg (2010) and Bieńkowski (2014). Possibly the title 'Classification, Reconstructed Phylogeny, and Geographic History of the New World Members of Plateumaris Thomson, 1859' of Askevold (1991) suggested that this publication dealt only with new world Plateumaris species and did not contain relevant information on Palaearctic Plateumaris species or their subgeneric statuses.

Diagnosis of the genus Plateumaris Thomson, 1959.

Askevold (1991) detailed the diagnosis so only the most necessary characters needed to distinguish the Plateumaris species from all other Donaciinae are listed below:

Sutural margin of elytron explanate apically, sutural interval sinuates distinctly before apex, lower sutural margin broadly exposed (Fig. 1A );

Elytral apex rounded, inner angle sharp, no outer angle protruding;

First abdominal segment as long as the others combined;

Host plants are typically Cyperaceae, but also a few other wetland plants.

The aedeagus of Plateumaris species and some other representatives of the Donaciinae consists of a median lobe which contains the endophallus and the lateral parameres (Fig. 1B ). The parameres are fused basally and distally, forming a ring around the median lobe. This parameric structure is the tegmen, composed of a ventral strut and a dorsal cap (for more details and functional descriptions see Askevold 1991 and Hayashi 2020). The frontal view towards the apex of the median lobe and of the cap of tegmen are usually very characteristic of each Plateumaris species and therefore suitable to distinguish them in most cases. Some species can be distinguished only by subtle morphological characters of their endophallus.

Biology.

Reed beetles live on plants in wetlands. The larvae develop attached to the roots in the sediment and live as sap suckers gnawing a hole into the root. They breathe by tapping the aerenchyma of the plant using two hollow abdominal hooks, which are connected to their tracheal system; therefore, they can live even in anoxic mud ( Böving 1910). Adults remain mostly above the surface sitting on aquatic plants but are able to hide under water while the ventral hairs serve as plastron respiration ( Rheinheimer and Hassler 2018). The larvae pupate at the end of their second summer in a cocoon, attached to the root of the food plant. The beetle overwinters in an air-filled cocoon and emerges the following spring. In warmer climates the larvae may pupate after their first summer ( Böving 1910; Kleinschmidt and Kölsch 2011).

The larval host plants are mostly members of Cyperaceae , but include some Juncaceae and Poaceae (e.g., Phragmites australis (Cav.) Trin. ex Steud.). Acorus calamus L. ( Araceae ), Caltha palustris L. ( Ranunculaceae ), and lris versicolor L. ( Iridaceae ) are also mentioned as food plants ( Borowiec 1984; Bieńkowski 2014). Most species are mono- or oligophagous, especially the larvae. Adult beetles feed on the leaves, although some species are pollen feeders, and some may also feed on petals. If a larva is attached to the root of a plant and gnawing traces are found, we can be sure that this is a host plant for this species. Adults may use a slightly broader range of plants. Several species feeding on pollen use the plants of their habitat. Therefore, adults can be observed on wetland plants that are mostly not larval food plants. The adults are active mainly in spring and early summer, sometimes also in autumn. No specific phenology data are provided here for the species because many have a wide distribution range and the time of “spring” differs between the populations within the Palearctic region.

Plateumaris species prefer habitats of wet sedge meadows, peat bogs, and fens, in contrast to Donacia species which live on aquatic plants with emerging parts and in contrast to Macroplea species which live on totally submerged aquatic plants.

Historical biogeography.

Plateumaris species are found only in the Holarctic region with ten species in the Palaearctic and 17 species in the Nearctic ( Askevold 1991); the latter occur mainly in Canada and the northern states of the USA. These two subregions have neither a Plateumaris species nor any other Donaciinae species in common, although molecular analysis shows that many Palaearctic Plateumaris species are more closely related to Nearctic species than to other Palaearctic species ( Askevold 1991; Hayashi 2020). Dispersal vicariance analysis and divergence time estimation revealed that the European and North American-Asian lineages diverged during the Eocene. Moreover, subsequent differentiation occurred repeatedly between North American and Asian species, which was facilitated by three dispersal events from North America to Asia and one in the opposite direction during the late Eocene through the late Miocene ( Kölsch and Pedersen 2008; Sota et al. 2008; Hayashi and Sota 2014).

Checklist and distribution.

A summary of the distribution of the Plateumaris species in the Palaearctic region is shown in Table 2 .

Palaearctic region: Plateumaris sericea has the largest distribution area of any Donaciinae species: it is recorded from Ireland and Great Britain to the whole of continental Europe, North Africa, and almost all Asian countries which belong to the Palaearctic region. Plateumaris weisei occurs from northern Europe to east Asia, from Siberia to northern China, Japan (Hokkaido), and South Korea.

Western Palaearctic region: Three species occur only in Europe and in Asia west of Lake Baikal: P. bracata , P. consimilis , and P. rustica .

Eastern Palaearctic region: Five species occur only in Asia east of Lake Baikal: P. amurensis , P. roscida , and P. shirahatai , and two species are endemic to the Japanese archipelago, P. akiensis and P. constricticollis .

Figures

Figure 1. Diagnostic characteristics of Plateumaris sp. A elytral apex with sutural margin broadly exposed, no outer angle protruding (arrowed; from Kaszab 1962) B typical structure of aedeagus in lateral view (from Askevold 1991). Abbreviations: ml median lobe, c cap of tegmen.