© Norwegian Journal of Entomology. 25 June 2015 New records of Metretopus alter Bengtsson, 1930 and Metretopus borealis (Eaton, 1871) (Ephemeroptera) in northern Norway, including confirmation of M. alter at the type locality after 90 years ANDERS KLEMETSEN, JOHN E. BRITTAIN & EVA ENGBLOM Klemetsen, A., Brittain, J. E. & Engblom, E. 2015. New records of Metretopus alter Bengtsson, 1930 and Metretopus borealis (Eaton, 1871) (Ephemeroptera) in northern Norway, including confirmation of M. alter at the type locality after 90 years. Norwegian Journal of Entomology 62, 117–128. The type localities for the Holarctic mayfliesMetretopus borealis (Eaton, 1871) and Metretopus alter Bengtsson, 1930 are in northern Norway, between Kautokeino and Karesuando in Finnmark County for M. borealis and along the small stream, Råvatnbekken, in Målselv, Troms County for M. alter. By combining new sampling, records in reports and theses and identification of museum material, new information on the distribution and ecology of both species is given. Larvae of M. alter were found in the type locality in 2012, 90 years after the initial collection, and in two other small streams in Balsfjord in 2012 and 2014. Råvatnbekken is a narrow, slow-flowing woodland stream with variable substrates and some macrovegetation. M. borealis was recorded in seven river systems throughout Troms and Finnmark, predominantly in the upper reaches. It was not collected in systems along the coast, indicating a continental distribution. While M. alter prefers smaller streams and avoids lakes, hard bottom substrates in moderately sized streams and lake littorals were typical M. borealis habitats. The streams had high diversities of mayflies and stoneflies and low abundance of M. borealis, while the lake littorals had low diversity and high abundance of M. borealis. This suggests less ecological interactions on lake shores allow high densities of M. borealis, although nutrient supply may also be important. The study confirmed two new localities forM.alter and many new localities for M. borealis in Norway. Key words: Ephemeroptera, Metretopus, type localities, distribution, habitat preferences, North Norway. Anders Klemetsen, Department of Arctic and Marine Biology, UiT The Arctic University of Norway, P.O. Box 6050 Langnes, NO-9037 Tromsø, Norway. E-mail: [email protected] John E. Brittain, Natural History Museum, University of Oslo, P.O. Box 1172 Blindern, NO-0318 Oslo, Norway. E-mail: [email protected] Eva Engblom, Limnodata HB, Gunnilbo 14, SE-73992 Skinnskatteberg, Sweden. E-mail: [email protected] Introduction see also Brittain et al. 1996) and 369 known species in the whole of Europe (Bauernfeind & Metretopus Eaton, 1901 in Norway. Soldan 2012). We follow the nomenclature of Bauernfeind & Soldan (2012) in this contribution. There are 48 known species of mayflies Four species: Siphlonurus aestivalis (Eaton, 1903), (Ephemeroptera) in the Norwegian fauna Metretopus alter Bengtsson, 1930, Metretopus (Kjærstad 2007, Artsdatabanken (2007–2012), borealis (Eaton, 1871) and Paraleptophlebia 117 Klemetsen et al.: New records of Metretopus in northern Norway strandii (Eaton, 1901) have been described as novae species with type localities in Norway. S. aestivalis and P. strandii were found in southern Norway, but the type localities of the Metretopus species are both in the northern, subarctic part of the country. In this contribution, we present new information on the distribution and ecology of the two Metretopus species in northern Norway with emphasis on Troms and Finnmark, the two northernmost counties. The mayfly family Metretopodidae has three genera and about 11 species (Bauernfeind & Soldan 2012). Two of the genera are found in Fennoscandia; the Palaearctic Metreplecton Kluge, 1996 with a single species, Metreplecton macronyx Kluge, 1996, in Finland, and the Holarctic Metretopus with two species, M. borealis and M. alter. M. borealis is circumpolar and has its Palearctic distribution from Denmark to the Far East. M. alter has been recorded from 62° N in Sweden and sporadically to north- eastern Russia and Mongolia (Bauernfeind & Soldan 2012). It is also present in Alaska in the western Nearctic (McCafferty 1994). A third species, Metretopus tertius Tiunova, 1999 has also been described from the Russia Far East (Tiunova 1999). M. alter and M. borealis are very similar and several authors have considered FIGURE 1. Distinguishing characters for mature larvae (> 7 mm) of Metretopus borealis (left) and them to be conspecific, but Engblomet al. (1993) Metretopus alter (right). Upper panel: bifid protarsal stated this to be untenable as there are distinct claws; anterior aspect; middle panel: female abdominal morphological differences, especially in the segment 9, ventral view; lower panel: male segment 9 male genitalia. The larvae are also very similar, with penis lobes, ventral view. After Engblom et al. and distinguishing characters were unknown (1993). until Engblom et al. (1993) described them from Sweden. Today they are accepted as close but given as “Finmark (province), between Kauto- distinct species (Engblom 1996, Bauernfeind keino and Karaswando” (Bauernfeind & Soldan & Soldan 2012). The family affiliation of the 2012: 82), but the precise location will probably genus has been unclear until recently. Brittain never be established. The type material is et al. (1996) placed it in Amelotropodidae and deposited in the Dale Collection, University Engblom (1996) placed it in Siphlonuridae, but Museum, Oxford, UK (Kimmins 1960). The type noted that this was for practical reasons while locality for M. alter is given as Raavand in “Nord- awaiting a critical review of the group. In the Norwegen, inneres Tromsø” by Bauernfeind & recent treatise on European mayflies (Bauernfeind Soldan (2012: 81), clearly with reference to, but & Soldan 2012) Metretopodidae are defined as a without direct citation from, Bengtsson (1930) monophyletic family with several apomorphies where the species is described. Inneres Tromsø including a characteristic bifurcation of the tarsal was a biogeographic region used by Bengtsson claws of the fore legs in the larvae (Figure 1). (1930) but for a reason not indicated, Bauernfeind The type locality for M. borealis is vaguely & Soldan (2012: 81) wrongly placed the type 118 Norwegian Journal of Entomology 62, 117–128 (2015) locality in Nord-Trøndelag County at 63° 31´N / differences between M. borealis and M. alter 11° 13´E, not in Troms County close to 70°. The habitats in northern Norway. type material is deposited at Tromsø University Kjærstad (2007) noted that the probable reason for Museum, UiT The Arctic University of Norway the lack of records in Norway was that potential (hereafter Tromsø Museum). habitats had not been investigated. In the present A comprehensive field survey of insects contribution, we intend to amend this lack of in freshwater and humid habitats was recently knowledge by: (1) making a systematic search for undertaken in Finnmark County (see Ekrem et al. information on the genus in little known reports 2012). Our knowledge of the freshwater fauna is and theses on aquatic insects in northern Norway; deficient in this very large county, with its high (2) identifying Metretopus larvae in the collection diversity of freshwater systems on the border of Tromsø Museum; and (3) sampling benthos in between the European arctic and boreal climate the type locality of M. alter and other localities zones. In this paper, we follow up the Finnmark in the Målselv river system, Troms County. We initiative, and particularly the contribution on expected that these efforts would add new records mayflies by Kjærstad et al. (2012), with new for both M. alter and M. borealis in Norway and information on the distribution and ecology provide information on their distribution and of the two species of Metretopus in Finnmark habitats in the northern part of the country. We and Troms. In Norway M. alter was not found also wanted to document whether M. alter is still outside the type locality for a long time until one present in the type locality, 90 years after its initial additional record came from the stream Gargiaelva discovery and provide a description of the type in Alta, Finnmark in 1986 (Engblom et al. 1993). locality. However, there were still only two localities, and M. alter was included in the Norwegian Red List The description of M. alter. from 1998 (Kjærstad 2007). In contrast, Engblom et al. (1993) mapped 69 and 31 localities for In 1930, Simon Bengtsson (Lund, Sweden) M. alter in Sweden and Finland, respectively, was invited to identify the collection of concluding that it has a more northern distribution Ephemeroptera in Tromsø Museum (Bengtsson than M. borealis. Several records of M. alter were 1930). The material consisted of winged stages close to the Norwegian border, suggesting that collected by curator T. Soot-Ryen in Troms and the species had a wider distribution in Norway Finnmark in the 1920s, but also contained earlier than had been documented, and it was therefore samples from Johan Sparre Schneider. Bengtsson excluded from the 2006 and 2010 revisions of the noted that this was not a small collection (“nicht Norwegian Red List (Kjærstad et al. 2010). geringe Material”, Bengtsson 1930: 4) and his Engblom et al. (1993) compared the habitats work increased the number of mayfly species in of these two species in Sweden and Finland. north Norway from 7–8 to 22. Two species were M. borealis was found mainly in streams, but described as new to science, Paraleptophlebia occasionally also in lakes, while M. alter with tumida Bengtsson, 1930, (later regarded a a few exceptions in pools was restricted to synonym of Paraleptophlebia werneri Ulmer, running waters. Their lotic habitats overlapped 1920; Landa 1969) and Metretopus alter. The considerably in chemical, physical and biotic description of M. alter included characters for characteristics, but there were significant imagines of males and females that separated it differences in stream size. M. borealis occurred in from M. borealis. Bengtsson (1930) applied the streams up to 100 m wide and with a mean width name M.