Research Article |
Corresponding author: Frank Van de Meutter ( frank.vandemeutter@inbo.be ) Academic editor: Claudia Buser
© 2022 Frank Van de Meutter.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Van de Meutter F (2022) Description of the female of Platycheirus altomontis Merlin & Nielsen in Nielsen, 2004 (Diptera, Syrphidae) with notes on the occurrence and hilltopping behaviour of rare French montane and Alpine Syrphidae. Alpine Entomology 6: 65-76. https://doi.org/10.3897/alpento.6.81676
|
A focused search in very high (2500–3200 m asl) Alpine mountain tops in France resulted in the discovery of the very rare Alpine-endemic syrphid Platycheirus altomontis Merlin & Nielsen in Nielsen, 2004, including its hitherto unknown female. A description of the female is given and further complemented with behavioural observations of this species with special reference to hilltopping. Additional records and behavioural observations are provided for rare and new species for the French fauna from the montane and Alpine habitat with focus on species of high altitude (>2750 m) and hilltopping behaviour. The species Rohdendorfia alpina Sack 1938 is new to France and was observed in large numbers at scree slopes above 2750 m and males were found sitting at hilltops up to 3200 m. Hilltopping behaviour of Syrphidae was observed over the whole altitudinal range visited, and multiple species engaged in this behaviour even at above 3000 m. Hilltopping appears to be more common in some genera (e.g. Parasyrphus and Pipizella) than in others and may be linked to specific phenotypes in some species. The latter was observed for the species Cheilosia melanura (Becker, 1894) of which at high hilltops much smaller males were found than at lower altitudes.
hilltopping, Rohdendorfia, France, Alps, mate finding strategy
France has the largest expanse of territory of any state currently within the European Union, and also has the longest list of Syrphidae, with 555 species (
Hilltopping is a mate-finding strategy encountered in many insect families (Skevington 2008). This interesting behaviour is very common in Syrphidae but has received little attention so far in literature (Waldbauer 1990;
The main objectives of this study are to answer the above questions: provide an overview of the hover fly community of the Alpine habitat with special focus on very high mountains (>2800 m), and determine which species use hilltopping behaviour and to what height this behaviour occurs. Several expeditions to high mountain areas in France (mainly the Alps and the Pyrenees) were conducted with special focus on high mountain hover fly communities and on their hilltopping behaviour. The presence and behaviour of rare species will be discussed and an overview generated of the species that showed hilltopping behaviour. Lastly, a description of the hitherto undescribed female of Platycheirus altomontis Merlin & Nielsen in Nielsen, 2004 is provided.
Between 2019 and 2021, several excursions were undertaken by the author to the French Alps, the French Pyrenees and the Ardèche. An overview of the reported excursions, their duration and the altitudinal range covered can be found in Table
Overview of the visited mountain regions in France with indication of the visited localities, the dates, and the investigated altitudinal range.
Region: localities | Period | Year | Altitudinal range (m asl) |
---|---|---|---|
French Alps: Vars, Villar-d`Arêne, Freissinières | 19–26 June | 2020 | 770–2430 (mainly 1700–2300) |
French Alps: Vars, Villar-d`Arêne, Molines-en-Queyras | 25–28 July | 2020 | 1160–3140 (mainly >2500) |
French Pyrenees: Bagnères-de-Bigorre, Bordes-Uchentein. | 14–19 July | 2020 | 930–1950 (mainly 930–1350) |
Ardèche: Lafarre, St.-Jeure-d’Andaure | 4–9 August | 2021 | 550–1250 |
Hoverflies were studied under a WILD M5a stereomicroscope (magnification 6-50x). The terminology used to describe the female of P. altomontis followed
No strict criteria exist for recognizing an insect present at a hilltop as a hilltopper. Skevington (2008) explains that true hilltopping is a mate finding strategy whereby males await (often virgin) females, which implies that the population of a hilltopping species should be strongly male-biased. Also males should execute some sort of mate finding behaviour, but this behaviour can be very different among species and is therefore difficult to define. For this study, a species was considered as doing hilltopping when the species was present at or near a hilltop, when a clear male bias was seen and/or when males displayed some behaviour that could be recognized as mate finding behaviour (hovering, patrolling or sitting on stones, trees or other landmarks, chasing other insects). Searching for hilltopping insects anticipated on the known partitioning of the hilltop by different species (Skevington, 2008). We therefore investigated different niches at the hilltop (bare stones, small trees, tree trunks, sheltered versus exposed side of the hilltop, etc…), at different distances from the summit.
FRANCE • 1 female, 05-Hautes-Alpes, Molines-en-Queyras, near Pain de Sucre, 44.698°N, 6.991°E, 2780 m, 26 Jul. 2020; 3 males, 2 females, 05-Hautes-Alpes, Vars, La Mortrice, 44.574°N, 6.769°E, 3142 m, 27 Jul. 2020.
Two high mountain tops were searched and both produced P. altomontis. A female was found feeding on small white flowers near the top of the Pain de Sucre, and 3 males and 2 females were found on the top of La Mortrice. The females were visiting small flowers, the males were feeding or sitting on the stones, from which they made short flights, suggestive of hilltopping behaviour. The female of P. altomontis is unknown so far and is described below. Females of P. altomontis were identified as such because they occurred together with the males, and because they shared some typical characters also found in the males including the very dark legs, the very broad head, and the very long hairs on the head and thorax. A male P. altomontis is shown in Fig.
of the female of P. altomontis. The following description is based on the three collected females.
Head (Figs
Thorax (Fig.
Wing: Stigma light yellow. Wing covered with microtrichia, except cell bm, br and cua microtrichose apically, otherwise bare. Calypter yellow-white, haltere yellow-brown.
Legs: All legs completely dark with thin grey pollinosity, but tibiae narrowly yellow at base and femora yellow at their distal end. Legs entirely pale-haired. Coxae and trochanters of usual shape.
Abdomen (Fig.
Body length: 6–7 mm.
Of the 23 species in the Platycheirus ambiguus group, the females are as yet unknown for 8 species. In the key for females of
The female resembles the male of P. altomontis apart from the usual sexual dimorphism found within this genus.
All expeditions combined, a total of 205 species of Syrphidae have been observed in mountains in France by the author (see Suppl. material
Examined material. FRANCE • 1 male, 05-Hautes-Alpes, Villar-d’Arêne, Col du Lautaret, 45.029°N, 6.401°E, 2075 m, 21 Jun.2020; 2 males, 05-Hautes-Alpes, Molines-en-Queyras, near Pain de Sucre, 44.698°N, 6.991°E, 2780 m, 26 Jul. 2020; 2 males, 5 females, 05-Hautes-Alpes, Vars, near La Mortrice, 44.574°N, 6.760°E, 2844 m, 27 Jul. 2020.
Examined material. FRANCE • 2 males, 05-Hautes-Alpes, Villar-d’Arêne, Col du Lautaret, 45.029°N, 6.401°E, 2075 m, 21 Jun. 2020.
Examined material. FRANCE • 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 1780 m, 44.623°N, 6.716°E, 20 Jun. 2020.
Examined material. FRANCE • 2 females, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.623°N, 6.716°E, 1780 m, 20 Jun. 2020; 1 male, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.613°N, 6.743°E, 2010 m, 24 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.621°N, 6.721°E, 1792 m, 24 Jun. 2020.
Examined material. FRANCE • 1 male, 07-Ardèche, Lafarre, 45.058°N, 4.496°E, 550 m, 4 Aug. 2021; 1 male, 1 female, ibidem, 6 Aug. 2021.
Notes. Previously only known from one department in the Alps. On observation.org, however, a female E. alpina has been reported from Central France by Menno Reemer at Valcivières, indicating more populations or a metapopulation may be present in the mountainous of the south-central part of France.
Examined material. FRANCE • 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.611°N, 6.743°E, 2140 m, 20 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.605°N, 6.766°E, 2280 m, 22 Jun. 2020.
Both specimens were caught on flowering Salix sp..
Examined material. FRANCE • 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.605°N, 6.766°E, 2280 m, 22 Jun. 2020.
On flowering Salix sp..
Examined material. FRANCE • 1 male, 05-Hautes-Alpes, la Danchère, path to Lac Lauvitel, 1180 m, 44.982°N, 6.072°E, 25 Jul. 2019; 2 males, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.614°N, 6.746°E, 1950 m, 20 Jun. 2020; 1 male, 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.611°N, 6.743°E, 2140 m, 20 Jun. 2020; 1 female, 05-Hautes-Alpes, Freissinières, 44.712°N, 6.447°E, 2050 m, 23 Jun. 2020; 1 female, 05-Hautes-Alpes, Cervières, Le Laus, 44.849°N, 6.735°E, 1805 m, 25 Jun. 2020.
Notes. This species is poorly described in current literature but can be identified with
Examined material. FRANCE • 3 females, 05-Hautes-Alpes, la Bérarde, parc des Ecrins, 44.905°N, 6.316°E, 1910 m, 23 Jul. 2019; 3 males, 1 female, 05-Hautes-Alpes, la Grave, Le Chazelet, plateau des Emparis, 44.905°N, 6.332°E, 1800 m, 23 Jul. 2019; 1 male, 05-Hautes-Alpes, Molines-en-Queyras, vers col d’Agnel, 44.713°N, 6.919°E, 2090 m, 26 Jul. 2020; 2 males, 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.608°N, 6.731°E, 2345 m, 27 Jul. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.616°N, 6.723°E, 1825 m, 27 Jul. 2020.
Examined material. FRANCE • 2 females, 05-Hautes-Alpes, la Bérarde, parc des Ecrins, 44.905°N, 6.316°E, 1910 m, 8 Jul. 2005; 1 female, 05-Hautes-Alpes, Molines-en-Queyras, vers col d’Agnel, 44.713°N, 6.919°E, 2090 m, 26 Jul. 2020; 1 male, 05-Hautes-Alpes, Molines-en-Queyras, vers col d’Agnel, 44.700°N, 6.946°E, 2290 m, 26 Jul. 2020; 3 males, 4 females, 05-Hautes-Alpes, Molines-en-Queyras, vers col d’Agnel, 44.692°N, 6.971°E, 2576 m, 26 Jul. 2020; 1 male, 05-Hautes-Alpes, Villar d`Arêne, Col du Lautaret, 45.033°N, 6.403°E, 2050 m, 28 Jul. 2020; 1 male, 2 females, 07-Ardèche, Saint-Martial, Gerbier de Jonc, 44.843°N, 4.195°E, 1430 m, 6 Aug. 2021; 1 male, 1 female, 07-Ardèche Saint-Martial, 44.866°N, 4.195°E, 1400 m, 6 Aug. 2021.
Examined material. FRANCE • 1 male, 2 females, 09-Ariege, Bordes-Uchentein, Maison du Valier, 42.808°N, 1.049°E, 1380 m, 14 Jul. 2020.
Examined material. FRANCE • 2 males, 1 female, 05-Hautes-Alpes, la Grave, Le Chazelet, plateau des Emparis, 44.905°N, 6.332°E, 1800 m, 24 Jul. 2019.
Examined material. FRANCE • 5 males, 10 females, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.611°N, 6.743°E, 2140 m, 20 Jun. 2020; 5 males, 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.603°N, 6.759°E, 2320 m, 22 Jun. 2020; 1 male, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.613°N, 6.743°E, 2010 m, 24 Jun. 2020.
Notes. In the Alps a long series of Parasyrphus was collected (Figs
Examined material. FRANCE • 1 male, 1 female, 05-Hautes-Alpes, la Danchère, path to Lac Lauvitel, 44.982°N, 6.072°E, 1180 m, 25 Jul. 2019.
Found sunning on tree leaves in a small clearing within broad-leaved forest.
Examined material. FRANCE • 1 male, 1 female, 38-Isere, Mont-de-Lans, 770 m, 45.009°N, 6.068°E, 19 Jun. 2019. ITALY •: 2 male, 1 female, Oulx, Amazas Torino, 45.009°N, 6.826°E, 1160 m, 25 Jul. 2020.
Notes. Pipizella elegantissima was seen at the edge and along paths of broad-leaved forests on the lower, warmer slopes of the Alps, usually flying low through forest margin vegetation. Though it occurs at rather low elevation, it appears to be mountain species that is so far only known from the French and Italian Alps and the Italian Apennines (Speight, 2020).
Examined material. FRANCE • 1 male, 09-Ariege, Bordes-Uchentein, Maison du Valier, 42.802°N, 1.056°E, 1760 m, 14 Jul. 2020.
Examined material. FRANCE • 5 females, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.611°N, 6.743°E, 2140 m, 20 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.614°N, 6.746°E, 1950 m, 20 Jun. 2020; 3 females, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.605°N, 6.766°E, 2280 m, 22 Jun. 2020; 7 females, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.613°N, 6.743°E, 2010 m, 24 Jun. 2020; 1 female, 05-Hautes-Alpes, Cervières, Col d`Izoard, 44.820°N, 6.737°E, 2400 m, 25 Jun. 2020; 1 female, 05-Hautes-Alpes, Molines-en-Queyras, Fontgillarde, 44.718°N, 6.908°E, 2040 m, 26 Jul. 2020.
Notes. Platycheirus brunnifrons were always caught on late flowering Salix sp. at the edge of remaining snow patches except for the individual in July that was feeding on a yellow crucifer. The identification of the female P. brunnifrons was based on
Examined material. FRANCE • 1 male, 65-Hautes-Pyrénées, Bagnères-de-Bigorre, Tourmalet, 42.901°N, 0.158°E, 2010 m, 17 Jul. 2020.
Notes. Feeding on a low yellow crucifer on a dry scree slope.
Examined material. FRANCE • 1 male, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.605°N, 6.766°E, 2280 m, 22 Jun. 2020.
Examined material. FRANCE • 1 male, 2 females, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.611°N, 6.743°E, 2140 m, 20 Jun. 2020; 2 males, 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.605°N, 6.766°E, 2280 m, 22 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.603°N, 6.759°E, 2320 m, 22 Jun. 2020; 2 males, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.613°N, 6.743°E, 2010 m, 24 Jun. 2020.
Examined material. FRANCE • 3 males, 1 female, 65-Hautes-Pyrénées, Bagnères-de-Bigorre, Tourmalet, 42.808°N, 0.159°E, 2090 m, 17 Jul. 2020; 1 female, 05-Hautes-Alpes, Molines-en-Queyras, top Pain de Sucre, 44.691°N, 6.999°E, 3140 m, 28 Jul. 2020.
Notes. Both in the Alps and the Pyrenees found on scree slopes with sparse vegetation. A male is shown in Fig.
Examined material. FRANCE • 1 female, 31-Haute-Garonne, Portet-d’Aspet, 42.941°N, 0.858°E, 1025 m, 11 Jul. 2020.
Examined material. FRANCE • 1 female, 05-Hautes-Alpes, La Bérarde, parc des Ecrins, 44.905°N, 6.316°E, 1910 m, 7 Jul. 2005; 1 female, 05-Hautes-Alpes, La Bérarde, parc des Ecrins, 44.905°N, 6.316°E, 1910 m, 23 Jul. 2019; 1 male, 2 females, 05-Hautes-Alpes, Villar d`Arêne, Col du Lautaret, 45.026°N, 6.406°E, 2220 m, 21 Jun. 2020; 9 males, 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.603°N, 6.759°E, 2320 m, 22 Jun. 2020; 1 male, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.605°N, 6.766°E, 2280 m, 22 Jun. 2020; 1 female, 05-Hautes-Alpes, Freissinières, 44.712°N, 6.447°E, 2050 m, 23 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.613°N, 6.743°E, 2010 m, 24 Jun. 2020; 1 female, 09-Ariege, Bordes-Uchentein, Maison du Valier, 42.802°N, 1.056°E, 1760 m, 14 Jul. 2020; 2 females, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.608°N, 6.731°E, 2345 m, 27 Jul. 2020.
Notes. On 22.Vi.2020, a group of hilltopping males (>25) was found at the last larch Larix sp. above the treeline at 2320 m.
Examined material. FRANCE • 17 males, 11 females, 05-Hautes-Alpes, Molines-en-Queyras, near Pain de Sucre, 44.698°N, 6.991°E, 2780 m, 26 Jul. 2020; 7 females, 05-Hautes-Alpes, Vars, near La Mortrice, 44.574°N, 6.760°E, 2844 m, 27 Jul. 2020; 3 males, 1 female, 05-Hautes-Alpes, Vars, top La Mortrice, 44.574°N, 6.769°E, 3142 m, 27 Jul. 2020.
Notes. A species of bare scree slopes at high altitude. Though this species was never seen before in France, it is very common locally. The numbers listed above are only a fraction of the numbers seen in the field. Rohdendorfia alpina was found at both of the two high mountain tops visited in July 2020 and probably is present at many other mountain tops in the French Alps. At La Mortrice, male R. alpina seemed to perform hilltopping behaviour. A male and a female are shown in Figs
Examined material. FRANCE • 1 male, 1 female, 05-Hautes-Alpes, Molines-en-Queyras, vers col d’Agnel, 44.700°N, 6.946°E, 2290 m, 26 Jul. 2020; 1 male, 1 female, 05-Hautes-Alpes, Molines-en-Queyras, vers col d’Agnel, 44.713°N, 6.919°E, 2090 m, 26 Jul. 2020.
Examined material. FRANCE • 3 males, 05-Hautes-Alpes, La Bérarde, parc des Ecrins, 44.904°N, 6.332°E, 2400 m, 23 Jul. 2019.
Notes. All individuals were caught on a patch of disturbed and slightly fertilized patch of ground next to a refuge building with sparse pioneer vegetation of yellow crucifers. In the nearby more pristine habitat other Sphaerophoria species were found. It is the experience of the author, that many of the species of the Sphaerophoria rueppellii-group are linked to disturbed situations with pioneer vegetation: S. rueppellii in open lowland situations (ground works, riparian zone of streams,…) S. shirchan in recent forest clearings, and S. estebani in high mountain areas (scree slopes, human disturbances,…).
Examined material. FRANCE • 2 males, 1 female, 05-Hautes-Alpes, Villar-d’Arêne, Col du Lautaret, 45.029°N, 6.401°E, 2075 m, 21 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.605°N, 6.766°E, 2280 m, 22 Jun. 2020; 1 female, 05-Hautes-Alpes, Freissinières, 44.704°N, 6.435°E, 2240 m, 23 Jun. 2020; 2 females, 05-Hautes-Alpes, Molines-en-Queyras, vers col d’Agnel, 44.692°N, 6.971°E, 2576 m, 26 Jul. 2020.
Examined material. FRANCE • 1 male, 05-Hautes-Alpes, Vars, Val d’Escreins, 44.614°N, 6.746°E, 1950 m, 20 Jun. 2020.
During the above-mentioned visits to the French Alps, 13 species were observed hilltopping. Raw estimates of numbers and altitude at which the behaviour was performed are indicated in Table
Overview of the species observed hilltopping in the French Alps in June and July 2020. The estimated number of individuals and the elevation(s) (in m asl) of the hilltop(s) are indicated.
Species | Nr. (males) | Elevation (m asl) | Month |
---|---|---|---|
Cheilosia canicularis (Panzer, 1801) | 15 | 2345 | July |
Cheilosia melanura (Becker, 1894) | 25 | 2320 | June |
Didea alneti (Fallen, 1817) | 2 | 2320 | June |
Epistrophe leiophthalma (Schiner & Egger, 1853) | 1 | 3142 | July |
Eristalis tenax Linnaeus, 1758 | 3 | 3142 | July |
Eupeodes flaviceps (Rondani, 1857) | 2 | 3142 | July |
Parasyrphus kirgizorum (Peck, 1969) / tarsatus (Zetterstedt, 1838) | 25 | 2320 | June |
Pipizella calabra (Goeldlin, 1974) | 25 | 2320 | June |
Pipizella nigriana (Séguy, 1961) | 30 | 2320 | July |
Pipizella pennina (Goeldlin de Tiefenau, 1974) | 2 | 2320 | June |
Platycheirus altomontis Merlin & Nielsen in Nielsen, 2004 | 3 | 3142 | July |
Platycheirus tatricus Dušek & Láska, 1982 | 25 | 2320 | June |
Rohdendorfia alpina Sack, 1938 | 25 | 2780/3142 | July |
With a rather limited but focused search effort, several new species for the French fauna were discovered (see also
The high mountain habitat above 2800 m is probably undersampled for Syrphidae over much of Europe. Platycheirus altomontis was only recently described (
Platycheirus is mainly a northern genus, with nearly ¾ of all 63 European species occurring in Scandinavia, although many species also have isolated populations much further south in mountains (
Even at hilltops above 3000 m, P. altomontis was not the only syrphid species hilltopping: at La Mortrice also hilltopping males of Rohdendorfia alpina, Epistrophe leiophthalma (Schiner & Egger, 1853), Eupeodes flaviceps Rondani (1857) and Eristalis tenax Linnaeus 1758 were present. Earlier in spring, when high hilltops are too cold and covered with snow, lower hilltops and clear landmarks on the slopes, such as large boulders or the last trees above the tree line are locations where hilltopping takes place. On 22 June 2020 together with Parasyrphus kirgizorum/tarsatus and Platycheirus tatricus also Cheilosia melanura, Didea alneti, Pipizella calabra, P. nigriana and P. pennina were present. Some of these species were hardly found elsewhere during the period of investigation. Hilltopping males formed loose swarms (C. melanura, P. tatricus) next to the landmarks, or sat on the landmarks (other species). Hilltopping is a mate finding strategy that is believed to be especially prevalent (and rewarding) in rare species (Skevington 2008), however, very often also more common species engaged in hilltopping. Males of the very common Cheilosia melanura were seen hilltopping, but intriguingly they were all small individuals compared to the larger males of the same species that were found hovering in forest clearings at lower altitudes. Assuming no cryptic speciation is involved, this suggests hilltopping can simply be part of the portfolio of mate finding strategies found within a species, both common and rare, but in this case also that it may be an alternative mating strategy related to specific phenotypes (Hutchings and Myers 1994). There may also be some phylogenetic dependence in hilltopping behaviour: in some genera this behaviour is very common (e.g. many species of Parasyrphus and Pipizella) whereas it is never seen in other (e.g. Sphaerophoria and Paragus). More research however is needed, in the first place to establish in which species this behaviour occurs and next into how it evolved and why it occurs.
I would like to thank Lisa Fisler for some valuable comments on a previous version of the text. I am indebted to Martin Speight and especially Sander Bot for making the high-quality photographs.
Table S1
Data type: excel file
Explanation note: Table S1. 205 species of Syrphidae, that have been observed in mountains in France.