Andrena amieti Praz, Mueller & Genoud

Praz, Christophe, Mueller, Andreas & Genoud, David, 2019, Hidden diversity in European bees: Andrenaamieti sp. n., a new Alpine bee species related to Andrenabicolor (Fabricius, 1775) (Hymenoptera, Apoidea, Andrenidae), Alpine Entomology 3, pp. 11-38 : 16-22

Andrena amieti Praz, Mueller & Genoud sp. n. Figs 11, 12, 15-17, 20, 22, 24, 26, 27, 29-31, 33, 37, 39, 40, 42, 44, 46-48, 50, 52, Suppl. material 2: S1.

Type locality.

Switzerland, Canton of Bern, Municipality of Kandersteg, Northern shore of Lake Oeschinen [Oeschinensee] 46.502N 7.723E, 1590m. This locality is located within the Unesco World Heritage site "Swiss Alps Jungfrau-Aletsch" (Fig. 7).

Holotype.

Female of second generation, pinned (Figs 15-17, 26). Original labels: 1. "CH Oeschinensee , 621750/150000, 1640m, 6.vii.2014, leg. J. Litman 029472 ". 2. " ACU 29472 , GBIFCH00103472 " [unique identifier with a graphical barcode]. 3. "Voucher specimen for DNA extraction, Sample 1284, Christophe Praz, University of Neuchâtel” [yellow label, printed]. 4. Holotype female Andrena amieti sp. n. Praz, Müller & Genoud [red label, printed]. Deposited in MHNN.

Paratypes.

250 males and 237 females from various localities in France, Switzerland, Italy, Germany and Austria (Suppl. material 1).

Note.

The description and diagnosis are based on Alpine populations of this species. Southern Italian specimens (Suppl. material 2: Fig. S1) are slightly divergent in the colour of the vestiture; this variation is presented at the end of the description.

Diagnosis.

In the female sex, Andrena amieti sp. n. is highly similar to A. bicolor and A. allosa . All three species can easily be separated from A. montana by the dark prepygidial and pygidial fimbria (Fig. 37) (orange-brown in A. montana ; Fig. 38) and by the presence of at least some dark hairs laterally on the mesosoma (Fig. 15) (hairs on lateral parts of mesosoma entirely brownish-grey in A. montana ). The female differs from A. bicolor in the presence of comparatively long dark hairs on the mesonotum (Fig. 26), usually also on the scutellum; these dark hairs are intermixed with longer, orange brown or grey brown hairs, and many of them are longer than half the length of the light brown hairs. In A. bicolor , there are either no dark hairs on the mesonotum and scutellum, or only very short dark hairs on the mesonotum, their length being visibly smaller than half the length of the light brown hairs. In addition, there are in most cases numerous dark hairs on the propodeum in A. amieti sp. n. (all hairs usually light in A. bicolor ), the light hairs on T1-T4 are snow white (Fig. 33) (always yellowish-white in fresh specimens of A. bicolor ; Fig. 34), and some hairs between the antenna are always grey-brown (Fig. 16) (hairs between the antennae commonly entirely dark in A. bicolor , although sometimes also grey-brown).

The female of A. amieti sp. n. differs from that of A. allosa by the shorter clypeus with convex preapical area (Fig. 17) (clypeus produced apically, preapical zone flattened medially in A. allosa ; Fig. 18) and the short malar space (Fig. 22) (malar space as long as the basal width of antennal segment 3 in A. allosa ; Fig. 23); in addition, A. allosa has shagreened, more sparsely punctate tergal discs (especially medially on T2), the margin of T2 hardly impressed medially (Fig. 35), and comparatively longer mouthparts (compare Figs 24, 25).

The male of A. amieti sp. n. (Figs 39, 42) is similar to that of A. bicolor , A. allosa and A. montana , and superficially also to that of A. ruficrus . Separation from the male of A. bicolor may be difficult in worn specimens. In A. amieti sp. n., the light vestiture on mesosoma and metasoma is greyish-white without yellowish hue (Figs 39, 42, 50) (hairs on dorsal side of mesosoma and first terga with yellowish hue in fresh specimens of A. bicolor ; Fig. 51). The vestiture is comparatively long on the terga (Fig. 50), in particular medially on T4, the apical fringe of hairs is longer than the tergal margin (in A. bicolor fringe of hairs as long as or shorter than tergal margin; Fig. 51). The disc of T4 has at most a few isolated, dark hairs (disc of T4 with numerous dark hairs in A. bicolor ). Lastly, the facial vestiture (Figs 39, 42) is on average lighter than in A. bicolor , at least some grey hairs are found between and around the antennal sockets (in A. bicolor frequently entirely dark).

The male of A. amieti sp. n. is highly similar to that of A. allosa , especially in the first generation ( A. allosa has only one generation). Differences are summarized in the key: the maxillary palps are comparatively slightly shorter in A. amieti sp. n. (Fig. 44) than in A. allosa (Fig. 45), and in A. amieti sp. n. the head is comparatively short and broad with little protruding clypeus (Fig. 42) (head comparatively long with protruding clypeus in A. allosa ; Fig. 43). In addition, the first recurrent vein usually enters the second submarginal cell in or near its middle and the second submarginal cell is subquadrate or longer than broad (Fig. 48) (in A. allosa , the first recurrent vein enters the second submarginal cell in its basal half, second submarginal cell broader than long; Fig. 49).

In its vestiture, the male of A. amieti sp. n. is similar to that of A. montana ; the best diagnostic characters are the shape of the labral appendix, which is wider than long in A. amieti sp. n. (Fig. 40) and as long as apically wide in A. montana (Fig. 41), and the width of the penis valves and of the gonostylus: the gonostylus is more slender and the penis valves broader in A. montana (Fig. 61) than in A. amieti sp. n. (Fig. 52), although for these genitalic characters direct comparison with reference material is necessary. In addition, the mesonotum is nearly entirely shagreened in males of A. montana , while it is at least partly shiny in males of the second generation of A. amieti sp. n. (Fig. 47). Lastly, males of A. amieti sp. n. are also superficially similar to those of A. ruficrus , which usually have the apex of the hind tibia partly orange and the clypeal vestiture entirely show-white; in addition, the penis valves are broader basally in A. ruficrus (Fig. 60) than in A. amieti sp. n (Fig. 52).

Description.

Female: Body size and proportions: Very similar to A. bicolor . Body length approximately 9mm, slightly smaller on average than A. allosa (body length approximately 9.5mm-10mm). Head slightly broader than long (Fig. 16), clypeus broader than long. Malar space short (Fig. 22), as in A. bicolor , shorter than in A. allosa (Fig. 23), length without impressed area at most equal to half the base of third antennal segment. Gena slightly broader than compound eye in lateral view. Interocellar distance approximately 2 times diameter of lateral ocellus. Ocelloccipital distance approximately 0.9 times diameter of lateral ocellus. Third antennal segment longer than fourth and fifth together, the latter two broader than long, segments 6-11 subquadrate, 12 longer than broad (Fig. 16). Labral process trapezoidal, its apical width larger than its length (Fig. 20), comparatively broader than in A. montana (Fig. 21). Mouthparts (Fig. 24) as in A. bicolor , shorter than in A. allosa (Fig. 25), in particular segment 4 of maxillary palpus only three times as long as apically broad (in A. allosa at least four times as long as apically broad), and segment 2 of labial palpus hardly longer than broad (in A. allosa at least twice as long than broad).

Wing venation: As in A. bicolor ; the first recurrent vein enters the second submarginal cell in its middle or nearly so, and second submarginal cell subquadrate or longer than broad (Fig. 27) (in A. allosa , the first recurrent vein usually enters the second submarginal cell in its basal half; second submarginal cell broader than long; Fig. 28).

Integument colour: As in A. bicolor , integument black or dark brown, including flagellum and tegulae, apical margin of T1-T4 slightly lighter, tarsal segments 2-4 dark orange-brown, tarsal claws weakly ferruginous, hind tibial spurs light brown. Wing venation (including stigma; Fig. 27) predominantly brown as in A. bicolor .

Vestiture: Entire body vestiture made of simple to weakly branched hairs, more strongly branched hairs are present between antennal sockets, plumose hairs in propodeal corbicula, floculus, and prepygidial and pygidial fimbria. Hairs on head predominantly dark brown (Fig. 16), always with grey-brown to greyish-white hairs between antennal sockets (sometimes also around antennal sockets) and medially on vertex (in A. bicolor hairs on head often entirely dark); extent of grey vestiture on face variable but vestiture on average lighter than in A. bicolor . Hairs on mesosoma predominantly grey-brown, including on lateral and ventral sides (Fig. 15); hairs never bright orange-brown as in fresh specimens of A. bicolor ; mesonotum and usually also scutellum with intermixed long, grey-brown hairs and short, dark brown hairs (Fig. 26) (in A. bicolor either no dark hairs, or dark hairs shorter; see above); tegulae covered with short dark hairs (Fig. 26) (in A. bicolor light brown hairs); propodeum with intermixed grey and dark brown hairs (in A. bicolor usually without dark brown hairs); on lateral side of mesosoma, hairs on average lighter than in A. bicolor , sometimes entirely grey-brown (Fig. 15), dark hairs mostly with grey tips except sometimes under tegula, where hairs can be entirely dark; ventral part of mesosoma with grey-brown hairs becoming lighter apically. Leg vestiture nearly as in A. bicolor , flocculus grey-brown to whitish grey, on average lighter than in A. bicolor ; scopa yellowish brown, hairs on basitarsi 2 and 3 usually yellowish brown (in A. bicolor usually dark brown). T1 mostly covered with snow-white hairs (in A. bicolor yellowish-white), only a few isolated, dark hairs on anterior part of disc and numerous dark hairs on vertical anterior part of tergum; T2 and T3 covered with long, snow white hairs (Fig. 33) (in A. bicolor hairs yellowish-white, Fig. 34 and usually slightly shorter medially) forming very loose apical fringes, not hiding cuticula, discs with short, erect dark hairs, more numerous on T3 than T2; T4 covered with long, dark hairs forming loose apical fringe and with short, erect dark hairs on disc; prepygidial and pygidial fimbriae dark brown (Fig. 37). Sterna covered with dark, erect hairs, apical margin with apical fringes of dark, plumose hairs. In first generation, vestiture on average longer than in second, especially on clypeus, mesosoma and basal terga.

Sculpture: The variation observed in the sculpture of A. amieti sp. n. represents the middle range of the much wider scuptural variation observed in A. bicolor . Head: Facial fovea narrow (Fig. 16), as in A. bicolor ; clypeus (Fig. 17) densely punctured, more sparsely punctured laterally and basally than apically, there with shiny interspaces that are on average one puncture diameter wide, often with longitudinal irregularities (more so than in A. bicolor ); apical part of clypeus without flat area as observed in A. allosa ; frons unpunctured with numerous longitudinal ridges, as in A. bicolor . Mesosoma: mesonotum (Figs 29, 30) with well-visible punctures, interspaces nearly entirely dull and on average 3-4 puncture diameters in first generation (Fig. 29), shiny or silk-shiny and 2-3 puncture diameters in second generation (Fig. 30). Propodeum (Fig. 31) as in A. bicolor , propodeal triangle without punctures, dull, finely sculptured, anteriorly with a few longitudinal wrinkles, wrinkles less visible than in A. allosa (Fig. 32). Metasoma: terga sparsely punctured (Fig. 33), within variation observed in A. bicolor (Fig. 34), on average slightly more shagreened, especially apical tergal margin of T2 (compare specimens of same generation); first generation: disc of T1 very sparsely punctured, that of T2 sparsely punctured with interspaces equal to 4-5 puncture diameters; surface of tergal discs mostly shagreened to silk shiny, apical margins shagreened, mostly unpunctured, that of T2 weakly impressed medially, as in A. bicolor but more so than in A. allosa ; second generation (Fig. 33): punctation on average denser (interspaces equal to 3-4 puncture diameters on disc of T1, and 2-3 puncture diameters on disc of T2; sculpture of surface on average shinier, although usually still weakly shagreened; apical margins as in first generation, usually at least slightly shagreened.

Male: Body size and proportions: Body length approximately 7-8mm, similar to A. bicolor ; the two males of A. allosa examined were 8-8.5mm long. Head slightly broader than long, clypeus little protruding apically (Fig. 42) (in A. allosa , clypeus slightly more strongly protruding; Fig. 43); gena slightly broader than compound eye in lateral view; interocellar distance approximately 2.5-3 times diameter of lateral ocellus; ocelloccipital distance approximately equal to diameter of lateral ocellus; length of third antennal segment approximately 1.3 times length of fourth antennal segment (in A. bicolor third antennal segment often shorter, 1.1 times length of fourth segment), fourth slightly shorter than broad or subquadrate, segments 5-9 slightly longer than broad, 10-12 subquadrate, 13 longer than broad. Labral process trapezoidal, its apical margin slightly emarginate (Fig. 40) (in A. montana , process longer; Fig. 41). Mouthparts (Fig. 44) as in A. bicolor , slightly shorter than in A. allosa (Fig. 45) although differences not as striking as in female; segment 4 of maxillary palpus only three times as long as apically broad (in A. allosa approximately four times as long as apically broad).

Wing venation: As in female, the first recurrent vein usually enters the second submarginal cell in or near its middle; second submarginal cell subquadrate or longer than broad (Fig. 48) (in two examined specimens of A. allosa , the first recurrent vein enters the second submarginal cell in its basal half, second submarginal cell broader than long; Fig. 49).

Integument colour: As in female.

Vestiture: Entire body vestiture grey-white without yellowish hue (Figs 39, 42, 50) (light hairs always with yellowish hue in fresh specimens of A. bicolor ; this yellowish hue is not apparent in worn specimens), except as follows: facial vestiture varying from predominantly dark (as on Fig. 42), with only a few grey hairs between and around antennal sockets, on scape and on vertex medially, to nearly predominantly grey-white, with dark hairs restricted to apical and lateral parts of clypeus (facial vestiture often entirely dark in A. bicolor ; clypeus entirely covered by snow-white vestiture in A. ruficrus , and by light brownish-grey hairs and dark hairs laterally in A. montana ), area along inner margin of compound eye, and lateral parts of head. Mesonotum with a few isolated dark hairs among longer, grey hairs (Figs 46, 47); lateral side of mesosoma with a few isolated dark hairs below tegula. Propodeum with intermixed dark and light grey hairs. Legs mostly covered with grey-white hairs, hairs on external surface of all tibiae yellowish and on ventral surface of all tarsal segments yellowish-white. Surface of T1 with a few isolated, dark hairs on anterior, vertical part. Vestiture of T2-T4 snow white (Fig. 50) without dark hairs or at most with a few isolated dark hairs basally on disc of T4 (in A. bicolor , vestiture of T1-T4 yellowish white in fresh specimens, Fig. 51; disc of T4 predominantly covered with dark hairs, and with numerous dark hairs basally on disc of T3; dark hairs may appear light grey in worn specimens).

Sculpture: As for female, the sculpture of the male of A. amieti sp. n. is similar to that of A. bicolor , which is particularly variable. Head: clypeus densely punctured, interspace shiny or weakly shagreened, mostly narrower than one puncture diameter (Fig. 42); frons nearly unpunctured with numerous longitudinal ridges. Mesosoma: mesonotum in first generation (Fig. 46) entirely shagreened with sparse and little visible punctures, interspaces equal to 4-5 puncture diameters (similar to A. allosa or to first generation of A. bicolor ), in second generation (Fig. 47) nearly always with shiny area medially, punctation well-visible, on average slightly sparser than in second generation of A. bicolor , interspaces commonly over 3-4 puncture diameters (in A. bicolor rarely over 3 puncture diameters); propodeum as in female. Mesosoma: terga (Fig. 50) similar to A. bicolor , on average slightly more sparsely punctate and more shagreened, but within variation observed in A. bicolor ; punctures fine (slightly coarser on T1), interspaces often more than 5 times puncture diameters. Tergal margins usually partly shagreened (Fig. 50) (in second generation of A. bicolor often entirely shiny). Structure of S8 not visibly different from A. bicolor .

Genitalia: As on Fig. 52, very similar to Andrena bicolor (Fig. 53), dorsal lobe of gonocoxite weakly developed, gonostylus simple, regularly spatulate, external margin regularly rounded, penis valves narrow, hardly broadened basally.

Geographic variation.

In females from Southern Italy (Suppl. material 2: Fig. S1), the vestiture is nearly entirely grey-white, including on all parts of the mesosoma (isolated dark hairs on mesonotum and scutellum excepted), with no brownish hue, in contrast to Alpine specimens where the mesosonal vestiture is predominantly brown. No difference is found in vestiture colour in male specimens.

Etymology.

This species is named in honor of Felix Amiet, who has greatly contributed to our understanding of Central European bees, including the four species presented here.

Additional comments.

There are numerous species-group names currently treated as junior synonyms of A. bicolor ( Gusenleitner and Schwarz 2002). We carefully examined the description of each of these names if their type locality was located within the known range of A. amieti sp. n. The description of none of these species-group names points to A. amieti sp. n. (see also comments on A. croatica Friese, 1887 stat. rev., below). A. gwynana var. testacea Dalla Torre, 1877, described from Seefeld (Tyrol) and whose type material is presumably lost, originates from a region where A. amieti sp. n. might occur. The very brief original description merely mentions the “testaceous” hind tibia, which corresponds neither to A. bicolor nor to A. amieti sp. n., and which does not point to a differential character between these two species. For these reasons, we keep this taxon as a junior synonym of A. bicolor . Lastly, several taxa of Euandrena have been described from Ukraine, Central Asia or Russia ( Gusenleitner and Schwarz 2002). Given that A. amieti sp. n. appears to be restricted to the Alps, the Apennines and the Pyrenees, we consider it unlikely that any of these taxa will turn out to be conspecific with A. amieti sp. n.

Distribution.

Alps from Southern France to East Tyrol (Austria), including most of the Swiss Alps and the Allgäu Alps in Southern Germany, as well as the Italian Alps (Fig. 3); Monte Pollino in Southern Italy; one isolated record from the Pyrenees.

Phenology.

According to our data and field observations, Andrena amieti sp. n. has two generations per year (Fig. 5). The earliest males of the first generation were collected at the end of March, and some worn females collected during the first half of June probably belonged to the first generation (thus some females collected in June and seemingly belonging to the second “peak” on Fig. 5 were in fact most likely of the first generation). The second generation is active from mid-June to the first half of September. While the first generation was underrepresented in the examined material, intensive surveys in three Swiss localities where the species was found to be abundant consistently revealed the presence of two generations, with several females observed from May to early June, then numerous fresh males and fresh females observed from the end of June to mid-August.

Habitat.

Andrena amieti sp. n. has been found from an altitude of approximately 1000m up to slightly above the tree line at around 2300m in the Valais; one isolated record is from an elevation of 2500m (Fig. 5). Foraging females were observed in various habitats, often in clear forests but also in meadows, subalpine grasslands and scree slopes. Patrolling males, probably indicating the location of nesting aggregations, were regularly found on disturbed terrains with little vegetation, such as dry river beds, scree slopes or avalanche corridors (Fig. 8). In these presumed nesting sites, the soil was not particularly sandy, but rather consisting of gravel mixed with sand or clay.

Pollen host preferences.

Andrena amieti sp. n. collected the pollen from flowers belonging to 15 plant families (Table 3). Females of the spring generation exploited a wide spectrum of pollen hosts, among which Asteraceae , Rosaceae and Salix ( Salicaceae ) predominated; pollen of these three plant taxa represented 70.9% of the total pollen grain volume. In striking contrast, females of the summer generation exhibited a strong preference for the pollen of Campanulaceae , which contributed 79.9% to the total pollen grain volume and was recorded in 24 out of 28 scopal loads (Fig. 12). Field observations revealed that flowers of both Campanula and Phyteuma serve as pollen hosts among the Campanulaceae .