The subgenus Tipula (Arctotipula)

As its name implies, Arctotipula is mainly an Arctic and northern boreal subgenus, with some species occurring at high altitudes in mountainous regions (Savchenko Reference Savchenko1961; Brodo Reference Brodo and Harrington1990; Gelhaus et al. Reference Gelhaus, Podenas and Brodo2000; Oosterbroek et al. Reference Oosterbroek, Brodo, Lantsov, Starý, Bocher, Kristensen, Pape and Vilhelmsen2015). The subgenus is small, with 38 species and subspecies currently recognised. Of these, 14 are known from Russia (Oosterbroek Reference Oosterbroek2022) and only four occur in the tundra zone (Lantsov and Chernov Reference Lantsov and Chernov1987). Species of the subgenus Arctotipula have been found in the mountainous countries of Central Asia (Tuva), Eastern Siberia, and Mongolia, but they have not yet been found in the mountains of Central Europe (Alps) and the Caucasus (Dufour Reference Dufour1986; Lantsov Reference Lantsov2007). Two species with arcto-montane distributions were previously recorded from Wrangel Island: T. (A.) oklandi Alexander (Savchenko Reference Savchenko1961, p. 325, as T. (A.) ciliata) and T. (A.) salicetorum Siebke (Khruleva Reference Khruleva, Sokolov and Korneeva1987, p. 29; Lantsov and Chernov Reference Lantsov and Chernov1987, p. 26). An entity listed as “Tipula (Arctotipula) sp. (prope T. miyadii (Al.))” was included by Khruleva (Reference Khruleva, Sokolov and Korneeva1987); the term “prope” is Latin for “near.” We have established here that this specimen belongs to T. (A.) besselsoides Alexander, a newly recognised addition to the Wrangel Island fauna.

Adults of this subgenus can be recognised by their generally dark grey head and thorax, both covered with long dense setae, and dense setae on the coxae (Fig. 7A, B). Wings are unpatterned but lightly tinted and have a dark pterostigma that is enhanced by whitened areas on either side, and the calypters are glabrous. Antennae in both sexes are shorter than the thorax, and the scape is the longest segment and is densely covered with long setae; flagellomeres are almost cylindrical but slightly broadened at the attachment of the verticils (Fig. 7B). Males have the epandrium and hypandrium separated almost to the base. The epandrium is glabrous basally, and this section is usually obscured by the overlying eighth tergite, leaving only the densely setose distal section visible. The epandrium has a distal emargination, and the setae on either side and below this emargination are arranged in a characteristic pattern for Arctotipula, with their tips pointing towards the middle so that the lateral setae point towards the middle at a 45° angle (or less) and the central setae point caudally, with a gradual variation of slope in between (Figs. 7C, D; 9A; 10A, B). Ventrally, the hypandrium is divided shallowly or more deeply almost to its base; there are no lobes or other structures on either the hypandrium or on the eighth sternite. Females tend to be a few millimetres longer than their respective males but with abdomens in scale with that of the males. The female terminalia are reduced in length and narrower than the preceding segments.

Arctotipula larvae are also quite distinctive and easily separated from the larvae of other subgenera of Tipula by the five conical swellings on abdominal segments 2–7 – one on each venter and two in the pleural membrane on each side. The six lobes on the spiracular disk are conical, covered with minute hairs or glabrous and with a small group of setae at the lobe tips. The spiracles are relatively small and spaced far apart. The fourth-instar larva of T. (A.) salicetorum was described by Hofsvang (Reference Hofsvang1979) and Podeniene et al. (Reference Podeniene, Gelhaus and Yadamsuren2006). The latter reference also included descriptions and beautiful illustrations of four other species of Arctotipula from Mongolia. Gelhaus (Reference Gelhaus1986) described T. (A.) sacra Alexander from North America. The larvae of T. (A.) besselsoides and T. (A.) oklandi are still to be discovered.

Arctotipula larvae are entirely aquatic (Pritchard and Hall Reference Pritchard and Hall1971; Hofsvang Reference Hofsvang1979; Gelhaus Reference Gelhaus1986; Lantsov and Chernov Reference Lantsov and Chernov1987; Lantsov Reference Lantsov1997), yet except for T. (A.) conjuncta conjuncta Alexander (Podeniene et al. Reference Podeniene, Gelhaus and Yadamsuren2006), they lack the long fringe of setae around the lobes of the spiracular disk that is usually associated with aquatic species such as Angarotipula Savchenko and Prionocera Loew (Brodo Reference Brodo2017). The fringe of setae on the flexible lobes of these latter two aquatic genera allows the lobes to fold together and trap an air bubble over the spiracles, thus allowing the larvae to breathe. The spiracular lobes of Arctotipula are stout and unable to fold together. Pritchard and Stewart (Reference Pritchard and Stewart1982) showed that gas exchange occurs through the enlarged, thin-walled lobes on the spiracular disk, not through the spiracles, and suggested that the conical lobes on the abdominal segments may also be a source for oxygen uptake.

What we know about the Arctotipula larval life cycle is based on the excellent work by Pritchard and his colleagues (Pritchard and Hall Reference Pritchard and Hall1971; Pritchard Reference Pritchard1976; Pritchard and Stewart Reference Pritchard and Stewart1982) studying the immatures of T. (A.) sacra Alexander in the foothills of the Canadian Rocky Mountains, Kananaskis, Alberta, Canada. The black eggs are laid singly into the mud at pond edges or on floating mats of filamentous algae; each egg has a coiled filament that unfurls as an anchoring device. There are four instars, which is typical of other Tipulidae. Larvae usually overwinter for two years, first as a third-instar larva and a second winter as a fourth-instar larva (Pritchard and Hall Reference Pritchard and Hall1971). When the fourth-instar larva is ready to pupate, it crawls out of the water and into the damp substrate on the shore (Pritchard and Hall Reference Pritchard and Hall1971). These earlier findings suggest that Arctotipula species on Wrangel Island might need more than two years before pupation, given the harsh climate recorded for this island.

Fourth-instar larvae of Arctotipula are quite large, 28–42 mm long and about 4–8 mm wide (Gelhaus Reference Gelhaus1986; Podeniene et al. Reference Podeniene, Gelhaus and Yadamsuren2006). They live in shallow, highly oxygenated water and graze on the microflora in benthic sediments (Pritchard and Hall Reference Pritchard and Hall1971). The content of the midgut and the anatomy of the digestive system of the fourth-instar larvae of T. (A.) salicetorum Siebke, from the Taymyr Peninsula, Russia, were studied by Lantsov and Chernov (Reference Lantsov and Chernov1987). They found the remains of stonefly and chironomid larvae in the midgut. Predation was shown to be the dominant type of feeding in these specimens. In the Tuva ASSR, Russia, T. (A.) salicetorum was found in the highlands; the larvae develop along the edges of lakes and feed on detritus (Saaya Reference Saaya2021). Based on these findings, the biology of this subgenus has significant plasticity and probably varies within each species as well as in different parts of their ranges. Larvae and adults of crane flies, including the subgenus Arctotipula, make up a significant part of the trophic base of fish and semiaquatic insectivorous birds (Chernov Reference Chernov1985; Lantsov and Chernov Reference Lantsov and Chernov1987).

Distribution of Arctotipula species on Wrangel Island

The collection localities for the three species of Arctotipula are indicated by black numbers and symbols on the map of Wrangel Island (Fig. 1). More detailed and comparative information on the subzones, nature of the collection sites and their numbers, dates of collection, and the collectors for the recorded specimens are indicated in Table 1. The numbers of the collection sites in Table 1 correspond to the numbers in Fig. 1.

Table 1. Zonal position, localities, habitats, and collection dates of the three species of Tipula (Arctotipula) on Wrangel Island, Russia.

Zonal variants: nAT, northern variant of Arctic tundra subzone; sAT, southern variant of Arctic tundra subzone; nTT, northern variant of typical tundra subzone. Locality refers to the numbered collection sites (Fig. 1). Approximated coordinates are given in square brackets. a. s. l., above sea level; Collectors: OKh – O.A. Khruleva; UB – U.V. Babiy; LP – L.A. Potenko; AR – A.A. Rodionov.

Tipula (Arctotipula) besselsoides is newly recorded as occurring on Wrangel Island, even though it was the most abundantly collected of the three Arctotipula species on the island (Fig. 1). Adults were collected at six different localities, indicated by the black circles on the map (Fig. 1). The oldest specimen that we studied was a female from Rogers Bay (locality 5), collected on 10 July 1939 by Portenko (ZISP). We think that this is the same female specimen referred to as T. (A.) ciliata Lundstrom by Savchenko (Reference Savchenko1961, p. 327). No identification label was placed with this specimen. The other 36 specimens were collected in the island’s vast river valleys, mainly on pebble and sandy–pebble floodplains, with or without clumps of vegetation. From 1983 to 1989, eight adults were collected in all zonal variants except in the harshest climate in the polar desert zone. In the northern variant of the typical tundra subzone, represented on the island by three isolated enclaves (Fig. 1), the species was collected in locality 6 in the west and in locality 8 in the north but not in the warmest enclave in the centre of the island, despite the fact that research was conducted there for four seasons, from 1991 to 1994. In the current century, this species was rediscovered in localities 8 (2018) and 5 (2019), and it was additionally found in two more areas that had not been studied before (localities 1 and 7). The majority of adults were collected in 2019 during a special survey of Arctotipula habitats in river valleys. Two large series were collected in different variants of the Arctic tundra subzone: the northern (Neozhidannaya River, (Fig. 2), southwestern part of the island; locality 1) and the southern (Nasha River (Fig. 3), southeastern part of the island; locality 5). Thus, T. (A.) besselsoides is widely distributed on Wrangel Island; however, not counting 2019, it was mainly collected as singletons. Wrangel Island is the only Russian locality for this species, but it has been collected in considerable numbers in the Arctic regions of North America and in Greenland (Fig. 4; Brodo Reference Brodo and Harrington1990; Oosterbroek et al. Reference Oosterbroek, Brodo, Lantsov and Starý2007, Reference Oosterbroek, Brodo, Lantsov, Starý, Bocher, Kristensen, Pape and Vilhelmsen2015).

Tipula (Arctotipula) oklandi was found in 2015 in the enclave of the typical tundra subzone located in the warmest central part of Wrangel Island, locality number 10 (black asterisk, Fig. 1). It was collected in two habitats (pebble floodplain and at the edge of a high river terrace with a tundra–steppe–like sedge–forb community) about 300–400 m apart from each other along the river valley. The specimens were identified by V.I. Devjatkov.

A female identified as T. (A.) ciliata Savchenko (= oklandi) collected at Rogers Bay (locality 5) on 10 July 1939 by Portenko (Savchenko Reference Savchenko1961, p. 327; Lantsov and Chernov Reference Lantsov and Chernov1987, p. 26) is here identified as T. (A.) besselsoides and was mentioned above. An earlier record of this species from Wrangel Island is erroneous, but new material confirms its presence here. It is the rarest of the three species and has been collected elsewhere in Russia only on Novaya Zemlya, Taymyr Peninsula, in the Sakha Republic (near Verkhoyansk) and on the Northern Kurile Island of Paramushir, in Sakhalin Oblast (Savchenko Reference Savchenko1961; Lantsov and Chernov Reference Lantsov and Chernov1987; Fig. 5). It was mistakenly recorded from North America under the incorrect assumption that T. (A.) alascaensis Alexander is a synonym of T. (A.) oklandi (Brodo and Lantsov, unpublished data). Specimens cited by Savchenko (Reference Savchenko1961) from the tundra of Eastern Siberia (Kotelny Island, the lower reaches of the Yana and Indigirka rivers) have been found to belong to other species (Brodo and Lantsov, unpublished data) and so are not shown on the present study’s map. Currently, Wrangel Island is the northeasternmost point of detection of this species.

Fig. 5. Known distribution of Tipula (Arctotipula) oklandi. Wrangel Island, Russia, is denoted by a black star.

Tipula (Arctotipula) salicetorum is also rare on Wrangel Island. It was collected in 1985 and 1989 at three sites in the northern and eastern parts of the island, in the northern variant of the Arctic tundra subzone, a region with a harsh climate. More recently, it was found only once in the northern enclave of the typical tundra subzone (Mamontovaya River, locality 9; see black squares, Fig. 1). Specimens were collected on substrates similar to those the other two species were collected on. Tipula (A.) salicetorum has the most widespread distribution of the three species, extending across Sweden, Norway, Finland, scattered localities in northern Russia, and across subarctic North America from Alaska to Quebec (Fig. 6). It was not found in Greenland (Oosterbroek et al. Reference Oosterbroek, Brodo, Lantsov and Starý2007, Reference Oosterbroek, Brodo, Lantsov, Starý, Bocher, Kristensen, Pape and Vilhelmsen2015).

Fig. 6. Known distribution of Tipula (Arctotipula) salicetorum. Wrangel Island, Russia, is denoted by a black star.

Fig. 7. Male Tipula (Arctotipula) besselsoides: A, showing dense brown setae on head and thorax; B, antennae showing long setose scape and position and relative length of verticils on flagellar segments; C, epandrium showing rounded distal emargination and protruding ventral sclerite; D, epandrium depicting arrangement of setae on distal section. Scale bars: 1 mm.

Fig. 8. Tipula (Arctotipula) besselsoides: A, male, right gonostylus, ventro-medial view; B, male, inner and outer gonostyli, ventral view; C, male, inner and outer gonostyli, medial view; D, female terminalia, lateral view; E, female terminalia, ventral view. Scale bars: A–C, 0.5 mm; D–E, 1 mm. Arrow pointing to rounded shoulder of eighth sternite.

Fig. 9. Tipula (Arctotipula) oklandi: A, male epandrium; B, male right inner and outer gonostyli, medial view; C, male right inner gonostylus, ventral view; D, female terminalia, lateral view showing cercus longer than tenth tergite, smoothly and narrowly broader at base, hypogynial valve elongate, slender, truncately rounded lobe on eighth sternite; E, female terminalia, ventral view, broader and irregular contour of eighth sternite. Scale bars: A, 1 mm; B and C, 0.5 mm; D and E, 1 mm.

Fig. 10. Tipula (Arctotipula) salicetorum: A, male epandrium showing toothed bar behind distal lobes; B, male epandrium showing characteristic setal pattern and position of toothed bar beneath lobes; C, right inner and outer gonostyli, medial view; D, female lateral aspect, lobe of eighth sternite obscuring hypogynial valve. Scale bars: A, B, and D, 1 mm; C, 0.5 mm.

The composition of the Arctotipula species on Wrangel Island is a vivid example of the role of the geographical location of this island. Here, we find a species with a wide Holarctic distribution (Tipula (A.) salicetorum), a species for which Wrangel Island is the extreme easternmost locality (T. (A.) oklandi), and a species for which Wrangel Island is the westernmost locality (T. (A.) besselsoides). That the latter species is the most numerous and widespread on the island is quite unexpected.

The presence of species with a predominantly North American distribution is one of the features of the island’s biota. Among Diptera, examples are known from the families Agromyzidae (Nartshuk and Khruleva Reference Nartshuk and Khruleva2011, Reference Nartshuk and Khruleva2018), Muscidae (Sorokina and Khruleva Reference Sorokina and Khruleva2012; Sorokina and Tridrikh Reference Sorokina and Tridrikh2021), Syrphidae (Barkalov and Khruleva Reference Barkalov and Khruleva2021), Empididae (Khruleva et al. Reference Khruleva, Shamshev and Sinclair2021), and Hybotidae (Khruleva et al. Reference Khruleva, Shamshev and Sinclair2021). Since 2000, the species from the families Agromyzidae, Empididae, and Hybotidae are most numerous in the warmest central enclave of the northern variant of the typical tundra subzone, whereas Tipula besselsoides has never been found there.

Tipulid collections on Wrangel Island were made in seasons with different weather conditions. The last years of research fell during the period of warming of the Arctic climate, which began in the 2000s. Unlike the always-numerous mesophilic species Tipula (Pterelachisus) carinifrons carinifrons Holmgren, 1883, and Tipula (Vestiplex) wrangeliana Stackelberg, 1944 (Khruleva Reference Khruleva, Sokolov and Korneeva1987 and unpublished data), species of the subgenus Arctotipula were rare in collections throughout the entire period of research. The data obtained do not allow us to talk about a noticeable increase in their numbers in a changing climate, although in recent years, a rapid increase in the number of some other groups of Diptera has occurred on Wrangel Island (Khruleva and Zinchenko Reference Khruleva and Zinchenko2017; Grichanov and Khruleva Reference Grichanov and Khruleva2018, Reference Grichanov and Khruleva2020; Nartshuk and Khruleva Reference Nartshuk and Khruleva2018).