Ruizanthedella mutabilis ( Spinola, 1851 )

González-Vaquero, Rocío A. & Roig-Alsina, Arturo, 2019, The bee Ruizanthedella mutabilis Spinola (Hymenoptera: Halictidae): a very common but poorly known species studied using integrative taxonomy, Zootaxa 4563 (1), pp. 191-200 : 193-197

Ruizanthedella mutabilis ( Spinola, 1851)

Halictus mutabilis Spinola, 1851: 205 . Lectotype: female, Chile; Museo Regionale di Scienze Naturale, Torino, Italia. Designated by Moure and Hurd 1987: 171.

Halictus nigro-caeruleus Spinola, 1851: 204 . Lectotype: female, Coquimbo, Chile. Muséum National d’Histoire Naturelle, Paris, France. Designated by Moure and Hurd 1987: 172. New synonymy.

Halictus placidus Smith, 1879: 39 . Syntype: female, Chile; 17A.2664, Natural History Museum, London, England. Synonymized by Herbst 1907: 131.

Halictus nahuel-huapiensis Schrottky, 1908: 225 . Syntype: female, Lago Nahuel Huapi, Río Negro-Neuquén, Argentina. Lost. Synonymized by Schrottky 1913: 240.

This species can be easily recognized by the long hairs on the compound eyes (Figs 1,3), the bluish highlights on the head and mesosoma (Figs 1–4), and the basolateral patches of short, appressed hairs on the T2-T4 of the female ( Figs 5–7 ). The males are the inner surface of the legs yellow and the outer surface brownish, a row of short, hooked preapical setae, close to the apical margin of the S4 (s, Fig. 13 ), and the strong basal depression of the gonocoxite (bd, Figs 11–12 ). Most females are slightly longer than the males (Length: females 7.3–7.6 mm, males 6.2–7.6 mm).

The genital capsule of R. mutabilis was illustrated by Moure (1964: fig. 1, erroneously labeled as Ruizantheda proxima ( Spinola, 1851) ; Moure 1964: fig. 2 corresponds to Callistochlora chloris ( Spinola, 1851) , while Moure 1964: fig. 3 corresponds to Ruizantheda proxima ). The gonocoxite has a strong basal depression, clearly seen in dorsal and ventral views (bd, Figs 11–12 ); this basal depression is apparently absent in R. cerdai ( Rojas 2001: figs 1,4), and considerably weaker or absent in Ruizantheda ( Moure 1964: fig. 3; Cure 1989: fig. 13A; González- Vaquero & Roig-Alsina 2009: fig. 6; Coelho et al. 2014: figs 23–28) and Pseudagapostemon ( Cure 1989: figs 11B,D). The gonocoxite bears a retrorse lobe, which is ventrally projected (rl, Fig. 11 ). The inner side and the apex of the lobe bear simple setae caudally directed. Contrary to Ruizantheda , in Ruizanthedella the retrorse lobe has no basal projection. The gonostylus is a swollen structure, it is half-moon shaped ventrally, and it has very short, fine setae (gs, Fig. 11 ).

The apical margin of the S4 of the male of R. mutabilis is medially concave, and bears 9–10 short, preapical setae, arranged in a row on each side (s, Fig. 13 ); the setae have their apices bent down. In contrast, in the species of Ruizantheda the apical margin of S4 is either straight ( Cure 1989: fig. 13D; Coelho et al. 2014) or medially projected ( Cure 1989: Fig. 13E ; González-Vaquero & Roig-Alsina 2009: fig. 4), and it has similar short setae but these are juxtaposed and restricted to the medial area. Probably this is the case for R. cerdai , although the group of setae was mentioned as present on S5 ( Rojas 2001). In R. mutabilis the apical margin of the S5 is straight, and that of the S6 is convex. The S7-S8 ( Fig. 14 ) are similar to those of R. proxima ( Rojas 2001: fig. 6).

A syntype of H. placidus was examined through photographs kindly sent by David Notton (Natural History Museum, London); the reference to a holotype made by Moure (2007) is not valid. The specimen is in good condition and agrees with the features of R. mutabilis . Although the type of H. nahuelhuapiensis is presumed to be lost ( Moure 2007; Rasmussen et al. 2009), Schrottky’s description allows the recognition of the species. The features reported for H. nahuelhuapiensis agree with the specimens currently identified as R. mutabilis . Moure & Hurd (1987: p. 172) designated female lectotypes for H. mutabilis and H. nigrocaeruleus , considering both names as valid in their catalogue; they considered the data reported by Claude-Joseph (1926) as insufficient to support the synonymy of R. mutabilis and R. nigrocaerulea .

Variation. Spinola (1851) described H. mutabilis based on females and males with a reddish metasoma (except the black base of the T1). He did not mention any variation in the colour of the females, but for the males he stated that there was a “ type form” with a reddish metasoma ( Fig. 8 ), and three varieties: α, similar to the “ type form” but with apical terga black ( Fig. 9 ); β, similar to α, but with black basal rings on the mid terga; and ν, with metasoma entirely black ( Fig. 10 ). In spite of his varieties, Spinola recognized that there was a continuum in colouration among the specimens.

For Alfken (1913), Friese (1916) and Herbst (1917, 1922) the female of H. nigrocaeruleus described by Spinola was an “extreme variety” of H. mutabilis , and the “parallel form” to the male with dark metasoma. In spite of this, these authors listed both names as separate, valid species, and Friese (1916) presented a short description of the male assigned to H. nigrocaeruleus . Herbst (1922) agreed with Spinola that there was a continuum in colouration in both sexes, and that it was common to find different varieties flying together. Specimens varied in the colouration of the metasoma, while the colouration of the head, mesosoma and legs were constant ( Herbst 1922). According to this author, from 1,500 to 2,000 m a.s.l. only specimens with red metasoma can be found.

Variability in the colouration of the metasoma is common in halictids, for both sexes. For example, it was observed in specimens of R. proxima and Ruizantheda divaricata (Vachal, 1903) housed at MACN, reported for several species of Corynura ( González-Vaquero & Roig-Alsina 2017) and two species of Lasioglossum (Evylaeus) (Robertson, 1902) ( Miyanaga et al. 1999; Murao & Tadauchi 2011). Pereboom and Biesmeijer (2003) suggested that abdominal coloration in stingless bees ( Apidae : Meliponini ) might be involved in the regulation of body temperature, and that, in general, light bees might have an advantage over black bees in hot open lowland habitats, whereas black bees might have an advantage in wet habitats and mountains. In R. mutabilis , we have observed that the reddish metasoma is the most common colouration in the females ( Fig. 5 ), while a reddish metasoma with dark brown discs of the T4-T6 is the most frequently pattern observed in the males ( Fig. 9 ). However, some females have darkened areas on some terga ( Fig. 6 ), or the metasoma completely black to dark brown with bluish highlights ( Fig. 7 ). Darkened areas are also present in some males, but when the T1-T6 are black or dark brown they have no bluish highlights ( Fig. 10 ), and the sterna and the T7 are yellowish light brown (instead of reddish). The colouration of other structures was constant among the specimens examined, as well as the structure, the sculpture, and characters of the genital capsule of the male.

FIGURES 1‒4. Ruizanthedella mutabilis . 1, 3, head, 2, 4, habitus. 1–2, female, 3– 4 male. Scale lines: 1, 3, 0.5 mm; 2, 4, 1 mm.

Biology. Biological observations also support the synonymy between R. mutabilis and R. nigrocaerulea . The nesting biology of R. mutabilis was studied and illustrated by Claude-Joseph (1926). Females of this species dig galleries in the ground and the cells are in series, disposed one after the other in lateral tunnels, as in R. divaricata ( Michener & Lange 1958) . Claude-Joseph's (1926) observations suggest that R. mutabilis is communal. Although some notes about the life cycle of the species are dubious, Claude-Joseph (1926) knew about the colour variations described by Spinola (1851), and paid special attention to this species. After studying hundreds of nests, he said that specimens with different colouration of the metasoma emerge from the cells made by a single female, and that nests with only Spinola’s “ type form” are rare.

DNA Barcoding. We obtained eight DNA barcode sequences of lengths 658 bp, with no ambiguous base pair in any sequence, from specimens of R. mutabilis : 2 females (reddish metasoma; HALIC-236-12, HALIC-235-12) and 1 male (reddish metasoma with dark brown discs of T4-T6, Fig. 9 : HALIC-553-16) from Neuquén, Argentina, and 5 females from Santiago, Chile (reddish metasoma: HALIC-339-12, HALIC-340-12; dark-brown metasoma: HALIC-342-12, HALIC-343-12, HALIC-344-12) ( Table 1). The base composition had values similar to those of Caenohalictus ( González-Vaquero & Roig-Alsina 2013) , and some genera in the Augochlorini ( González-Vaquero et al. 2016). The maximum sequence diversity was 1.24%. All the sequences obtained were grouped under the same BIN (BOLD:AAJ7445) ( Fig. 15 ). Under the BIN species concept, all the specimens analyzed belong to the same species. When compared to DNA barcodes available from phylogenetically close genera of Caenohalictini, the distance to the nearest neighbor, R. proxima (HALIC-232-12), was 15.25%, and to R. divaricata (HALIC-345- 12) was 15.68%, while the distance to Pseudagapostemon pampeanus (Holmberg, 1886) (HALIC-238-12) was 18.61%.

Distribution. Ruizanthedella mutabilis is widely distributed in Chile, with records from Atacama to Los Lagos Region ( Moure & Hurd 1987). In Argentina, it is known to be restricted to the Nothofagus -dominated Andean forest of the south of Neuquén, west of Río Negro and northwest of Chubut. Since specimens with different colouration of the metasoma occur together in this area of Argentina, we consider it unlikely that colouration is directly linked to environmental factors. New records for this species include Chimpay in the north of Río Negro, and the San Jorge Gulf and Comodoro Rivadavia in the Atlantic coast of Chubut, all localities from the Patagonian steppe. Different varieties in the colouration of the metasoma were found in Chimpay, but only dark brown specimens were found in the Atlantic coast. Recently, two males with reddish metasoma were collected in the Natural Reserve Costanera Sur in the city of Buenos Aires. This is an unusual record, because it is 800 km from the northern most locality in Patagonia and the species has never been collected in the grasslands of the rolling Pampa, a region where the apifauna is relatively well known.

Material examined. ARGENTINA: Buenos Aires: ♂ 2, Reserva Ecológica Costanera Sur, 16-XI-2015, Compagnucci , Galvani & González V. ( MACN) . Neuquén: PN Lanín : ♀ 3 ♂ 1, Pucará, X / XII-1952, J. Schajovskoi ( MLPA) ; ♀ 1 ♂ 4, Cabecera E Lago Huechulafquen, 9/ 10-XII-1997, Roitman & Montaldo ( FAUBA) ; ♂ 1, Camino a Lago Tromen, 15-XII-2013, L. Compagnucci ( MACN, MACN-En 21807, HALIC-553-16) ; ♀ 1, Lago Lácar, 2-II- 2012, R. González V. ( MACN, MACN-En 9740, HALIC-235-12) . ♀ 1, Junín de los Andes, 2-II-2012, R. González V. ( MACN, MACN-En 9741, HALIC-236-12). San Martín de Los Andes : ♀ 1, 7-XII-1946, Hayward & Willink ( IMLA) ; ♀ 13, II-1974, L. Peña ( SEMC) ; ♀ 1 ♂ 2, 8k n SM Andes, 16/ 22-XI-1997, C. & M. Vardy ( BMNH) ; ♂ 1, 2k s SM Andes, Quitrahue , 17-XI-1997, C. & M. Vardy ( BMNH) . PN Nahuel Huapi: Isla Victoria : ♀ 1, XII-1954,

R.N. & J.S. de Orfila (MACN), ♀ 4, X-1963 ( MACN) , ♀ 1, X-1964, A.J. Giai ( SEMC) ; Cuyín Manzano , 21-XII- 2010, R. González V. ( MACN) . Paso Flores : ♀ 1 ( MACN) ; ♂ 1, 14-XI-1964, A. Giai ( MACN) . ♀ 1, Rinconada , XII-1965, A. Giai ( MACN) . Río Negro : PN Nahuel Huapi : ♀ 7 ♂ 1, Lago Fonck , 29-XII-1984 ( MACN) ; ♀ 5, 9/ 13- I-2000, D. Vázquez ( MACN) ; ♂ 4, Cerro Otto , 16/ 27-II-2000, C. Morales ( MACN) ; ♂ 1, Puerto Blest , 23-II-2000, C. Morales ( MACN) ; ♀ 1, Llao Llao , 30-XII-2000, C. Morales ( MACN) ; ♂ 1, ruta 258 10k sw San Carlos de Bariloche , 29-XI-1997, C. & M. Vardy ( BMNH) ; ♂ 1, 16k e San Carlos de Bariloche , 28-XI-1997, C. & M. Vardy ( BMNH) . San Carlos de Bariloche : ♀ 2 ♂ 1, XI-1964 ( MACN) ; ♀ 1 ♂ 9, 21-XI-1982, Orfila ( MACN) ; ♀ 1, 8-I-1964, A.J. Giai ( SEMC) ; ♀ 3, XII-1964, A.J. Giai ( SEMC) ; ♀ 2, 9- XI-1 964, A.J. Giai ( SEMC) . ♀ 6, Pichileufu , 30 km E Bariloche, XI-1964, A. Giai ( MACN) . ♀ 1, 9k ne El Bolsón , 11-XII-1997, C. & M. Vardy ( BMNH) . ♂ 10, El Bolsón , 11-XII-2017, R. González V. ( MACN) . ♀ 1, Río Villegas , Giai ( SEMC) . ♀ 2 ♂ 2, Chimpay , 5/ 8-X-1993, J. Farina ( MACN) . ♀ 4 ♂ 17, Chimpay , 5/ 8-X-1993, J. Farina ( MLS) . Chubut : PN Los Alerces : ♀ 1, Villa Futalaufquen , 13/ 18-XII-1997, C. & M. Vardy ( BMNH) ; ♀ 1, Laguna Larga , 5k e Villa Futalaufquen, 16-XII-1997, C. & M. Vardy ( BMNH) . ♀ 5, Golfo San Jorge , 1931, C. Ameghino ( MACN) . ♂ 6, Comodoro Rivadavia , petroquímica, 24-IX-2003, M.E. Arce ( MACN) . ♀ 646 ♂ 456 INTA Trevelin , 2005/2007, A.- I. Gravel ( MACN) .

CHILE: Valparaíso: ♀ 8 ♂ 19, El Canelo, XI-1946 /47, L. Peña Guzmán ( MACN) . ♀ 1, Río Blanco , 29-IV-

1918, Porter (MACN). Santiago : ♀ 3, Santiago, Caleu, 28-XI-2011, Mondaca & González V. ( MNNC: HALIC- 339-12, HALIC-343-12, HALIC-344-12). ♀ 2, Santiago, Caleu, 28-XI-2011, Mondaca & González V. ( UCVC: HALIC-340-12, HALIC-342-12). ♀ 3 ♂ 1, Ñuñoa, F. Claude ( MACN) . O'Higgins : ♀ 1, Las Nieves, 22-XI-1947, L. Peña Guzmán ( MACN) . Bíobío : ♂ 1, Ñuble, Las Trancas, 16-I-1989, J.E. Barriga ( MACN) . Araucanía : ♀ 9, 46k s Temuco, ca. Freire, 14-XII-1985, A. Roig-Alsina ( MACN) . Los Lagos : ♀ 3 ♂ 10, Pirehueico, Río Hua Hum, 30- XI-1985, A. Roig-Alsina ( MACN) . ♂ 1, Termas de Puyehue , 4/ 5-XII-1985, A. Roig-Alsina ( MACN) . ♂ 1, Chiloé , Chacao, 13-XII-1985, A. Roig-Alsina ( MACN) .

Figures

FIGURE 15. Neighbor-joining tree for specimens of R. mutabilis and phylogenetically close species, distances calculated using the Kimura 2-parameter model. The scale represents the number of substitutions per site.

FIGURES 5‒10. Colour variations of the metasoma of R. mutabilis. 5–7, females, 8–10 males. Scale lines: 1 mm.

FIGURES 11‒14. 11–12, Genital capsule, 11, ventral view, 12, dorsal view. 13, S4. 14, S7 and S8 fused, ventral view. Abbreviations: bd, basal depression of the gonocoxite, gs, gonostylus, rl, retrorse lobe of the gonocoxite, s, row of short setae. Scale lines: 200 µm.