Stictonectes rebeccae, Bilton, David T., 2012

Bilton, David T., 2012, Stictonectes rebeccae sp. n. from the Iberian Peninsula, with notes on its phylogenetic position (Coleoptera, Dytiscidae), Zootaxa 3188, pp. 42-54 : 44-48

Stictonectes rebeccae sp. n.

( Figs 1–7 )

Type locality. Spain, Avila, Sierra de Gredos, Río Barbellido in Garganta de Barbellido below ‘La Plataforma’, above Hoyos del Espino, 1750 m, 40°16’N 5°13’W ( Fig 10 ).

Type material. Holotype male ( NMW): “ 17/vi/2008 SPAIN, Avila, Sierra de Gredos, Garganta de Barbellido below ‘La Plataforma’, above Hoyos del Espino, ca. 1750 m, 40°16’N 5°13’W D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label.

Paratypes (333 exs.): Spain: 1 3 and 1 Ƥ ( NMW), 1 3 and 1 Ƥ ( MNCN), 1 3 and 1 Ƥ ( NHML), 1 3 and 1 Ƥ ( ZSM) and 2 3 7 Ƥ ( CDTB), 1 3 and 1 Ƥ ( NMW), 1 3 and 1 Ƥ (CGV) and 3 3 and 3 Ƥ ( CDTB) “ 31/v/2007 SPAIN, Avila, Sierra de Gredos, Garganta de Barbellido below ‘La Plataforma’, above Hoyos del Espino, ca. 1750 m, 40°16’N 5°13’W D T Bilton leg.”; 3 exs. ( CDTB) “ August 1999 SPAIN, Avila, Sierra de Gredos, Garganta de Barbellido below ‘La Plataforma’, above Hoyos del Espino, ca. 1750 m, 40°16’N 5°13’W D T Bilton leg.”; 1 3 and 3 exs. ( CDTB) “ 8/vi/1993 SPAIN, Avila, Sierra de Gredos, Garganta de Barbellido below ‘La Plataforma’, above Hoyos del Espino, ca. 1750 m, 40°16’N 5°13’W D T Bilton leg.”; 47 exs. (CHF; CJF) “ 27.5.2011 Spain, Avila prov.,Sierra de Gredos, ca. 5 km SW Hoyos del Espino”, “Rio Barbellido ca. 40.317N 5.213W ca. 1447 m, Fery leg.”; 1 ex. (CHF) “ 27.5.2011 Spain, Avila prov. Sierra de Gredos, ca. 7 km SSW Hoyos del Espino”, “Rio Barbellido, nr "Plataforma" ca. 40.283N 5.228W ca. 1705 m, Fery leg.”; 2 3 and 1 Ƥ (CHF) “ 3.8.89 España, Prov. Avila, Sierra de Gredos “Gredos” Tümpel., 1800 m Fery leg.”; 5 exs. (CHF) " 8.7.88 Espagna, S. de Gredos, Avila, Gredos, Bach, ca. 1800 m, Fery leg.”; 1 3 and 1 Ƥ (CHF) “ 3.8.89 España, Prov. Avila, Sierra de Gredos, 1800 m, Bach, “Gredos”, Fery leg.”; 2 exs. (CHF) “ 20.7.1999 E, Avila, Sierra de Gredos, Gredos, ca. 1800 m Gebirgsbach, Fery leg.”; 1 Ƥ (CHF) “ 13.6.1990 España, Prov. Avila, Sierra de Gredos, ‘Gredos’, Bach ca 1800m, Fery leg.”; 1 Ƥ (CHF) “ 19.7.2002 (E) Avila, Sierra de Gredos, S Hoyos del Espino, nr. “plataforma”, river, Fery leg.”; 1 ex. (CHF) “ 24.6.2005 (E) Avila, Sra de Gredos, S Hoyos del Espino, nr. Plataforma, ca. 1800 m, pond, Fery leg.”; 1 3 ( MNCN) DNA Voucher MNCN-AC17, “ Spain, Avila, Sa. Gredos, below refugio del Club Alpino, Hoyo del Espino, 1700m 31.5.2007, D.T. Bilton”; 1 Ƥ ( MNCN) DNA Voucher MNCN AC 8, “3 ES Madrid Sieteiglesias/ Ayo. Quiñón Jábalo / 907m N40º54'17" W3º34'32" /M131 pk15, 3.6.2007, I. Ribera & A. Cieslak”; 16 3 and 9 Ƥ (CJF) “ HISP. Salamanca 5.8.90 El Cabaco, S a Francia Peña d Francia 1030 m Fresneda & Leblanc”; 1 3 and 5 exs. (CHF) “ 12.8.89. España, Prov. Pontevedra, Estacas, Bach, Fery leg.”; 77 exs. (CHF) “ 12.8.89 España, Prov. Pontevedra, Lama, O. Pontevedra, Bach, Fery leg.”; 17 3 and 23 Ƥ (CHF) “ 1.7.1986 Spain, Lugo, Suoto-Cervantes, X Gonzales leg.”. Portugal: 2 3 (1 DNA voucher MNCN-AH72 with genitalia mounted on acetate strip below specimen) and 3 Ƥ ( IBE) “4 PORTUGAL Serra Estrela Sabugueiro, r. above village 1100 m N40°24’20” W7°37’43” I. Ribera leg. 12.5.2005 ”; 1 3 ( CDTB) “ 6/v/1993 PORTUGAL Viana do Castelo Serra da Peneda stream 5 km NE of Senhora da Peneda ca. 700m D T Bilton leg.”; 1 3, 1 3 and 2 exs. (CHF) “ 5.7.92 Portugal, Serra do Gerês, Portela de Leonte, Bach, Fery leg.”; 24 exs. (CHF) “ 4.7.92 Portugal, N Vila Real, Escariz, Bach, Fery leg.”; 43 exs. (CHF) “ 22.3.89 Portugal, Umg. Vila Real, Escariz, Bach, Fery leg.”; 1 ex. (CHF) “ 22.3.89 Portugal, Umg. Vila Real, Bach, Fery leg.”; 21 exs. (CHF) “ 5.8.89 Portugal, Umg. Vila Real, Escariz, Bach, Fery leg.” All with red paratype labels.

Description. Body highly arched, strongly pointed at the apex, and broadest around the middle of the elytra. Head black to brownish black, with the cervical region somewhat paler. Pronotum black with sides obscurely reddish outside the position of the lateral striae, especially towards the front angles. Elytra black with yellow to orange vittae, particularly well developed on the shoulders, and forming a characteristic pattern, which varies in extent both within and between localities ( Fig. 1 ). Antennae with four basal joints pale, 6–11 black, and joint 5 partially infuscated. Legs reddish-brown to black, with tibiae and tarsi darker in most specimens. Palpi pale, darkened apically. Head microreticulate, with even, isodiametric meshes, which are somewhat effaced, and a double punctuation; smaller, stellate punctures much more numerous than larger round punctures, and evenly distributed throughout ( Fig. 2 A). These stellate punctures have been noted in Stictonectes and related genera by a number of authors, and correspond to the ‘refractive spots’ referred to by Balfour-Browne (1940), and ‘asterisk reticulation’ of Wolfe and Zimmerman (1984). Larger punctures are relatively small and sparse on the clypeus, becoming denser and larger in diameter in the vertex. Larger punctures each bearing a short, peg-like sensilla, and tending to be deeper behind than in front ( Fig. 2 A). Pronotum transverse, with obsolete microreticulation, but with a clearly marked double punctation. Each side with a shallow lateral stria, approximately in the middle of the pronotal length, which occupies 0.25 – 0.3 of the length of the lateral margins (see Fig. 3A ). Small, stellate punctures numerous over entire surface, spaced approximately one puncture width apart ( Fig. 3 B). Larger punctures 2–4 puncture widths apart on the disc, becoming somewhat denser towards all margins, and also larger and deeper towards the hind margin ( Fig. 3 B). Large punctures with sides more steeply sloping towards their front margins, shallower behind. Each large puncture bearing a seta 2–4 puncture widths in length.

Setae particularly well developed in fresh specimens, giving a scantily pubescent appearance. Elytra highly arched and strongly rounded at sides, broadest just before middle, and markedly pointed at the apex. Lacking microreticulation, and with a double punctation resembling that on the pronotum. Small, stellate punctures much more numerous than large ones, spaced approximately 1 puncture width apart. Larger punctures resembling those on the pronotum in structure but denser on the elytra, where they are typically 1–2 puncture widths apart ( Fig. 4 A). As on the pronotum, setae give a sparsely pubescent appearance in fresh specimens.

Major part of the underside dark reddish-brown, with mouthparts, head, epipleura of pronotum and elytra and terminal abdominal segments paler, and hind coxal plates darker. Underside predominantly matt due to a well developed granular sculpture, which is absent only on the metacoxal process, and the head, which are consequently shinier than remaining areas. Metacoxal process lacking microreticulation; underside of head with a fine microreticulation composed of slightly transverse meshes. Elytral epipleura relatively wide, approximately twice the width of the middle femur at the level of the mid legs, and as wide as the hind femur at the level of the front margin of the first abdominal sternite. Surface of epipleura with the same granular sculpture as is present on sternites, and shallow, sparse, setose punctures, spaced approximately 1–2 puncture widths apart. Posterior margins of the metacoxal process rounded, conjointly indented in the middle, with bluntly pointed lobes. Metacoxal lines well developed, and process with long, sparse setae throughout its length. Metathoracic anepisternum, metasternum and metacoxae with setose punctures, which, like those on the pronotum and elytra, have their sides more steeply sloping towards front angles, and shallower behind. These punctures are relatively sparse on the metathoracic anepisternum and the centre of the metasternum, here being ca. 1–1.5 puncture widths apart, and <1 (usually approx. 0.5) puncture widths apart elsewhere. Areas between these punctures with well developed granular sculpture, generating the matt appearance overall. Abdominal sternites with setose punctures shallower than those on thoracic area, spaced 1–2 puncture widths apart on second and third sternites, becoming sparser to the abdominal apex, and absent on last sternite (7th). Granular sculpture of abdominal sternites finer and shallower than on the metacoxae, but generating the same matt appearance. Last abdominal sternite with granular sculpture particularly well developed, giving a crenulated appearance. Setae and punctures here restricted to marginal areas.

Male with median lobe curved in lateral view ( Fig. 5 A), with a slightly downwardly deflexed tip. Median lobe bluntly pointed in dorsal view ( Fig. 5 A). Internally, the median lobe contains an elongate, sac-like structure either side of the mid-line, covered in circular protuberances which resemble the surface of a pineapple ( Fig. 5 A). Paramere shape characteristic in lateral view, with an elongate terminal lobe, straight along its inner face, topped by a bluntly toothed internal projection and a relatively flat apex, which bears conspicuous setae and slopes at an angle of approximately 40° to the vertical ( Fig. 5 B, Fig. 6 ). Female with gonocoxosternum relatively broad and setose ( Fig. 7 A); gonocoxa with well-developed terminal and subterminal setae ( Fig. 7 B).

Dimensions as follows: Holotype TL 3.2 mm, MW 1.8 mm; paratypes TL 3.1–3.3 mm (mean 3.2 mm), MW 1.75–1.85 mm (mean 1.78 mm).

Variability. Specimens vary both within and between localities in the extent and shade of their elytral vittae, these being more or less developed, and darker or paler, as seen in Fig. 1 . The extent of deflexion of the apex of the median lobe also varies between specimens, the apex being almost straight in some individuals. Some variation is also seen in the shape of the paramere apex, specimens from the Sierra de la Peña de Francia, Serra Peneda, Serra do Gerês and Galicia having a somewhat more steeply sloping apex to the parameres, approximately 45–50° to the vertical, and the straight internal face is somewhat longer. Parameres of these specimens are otherwise identical to those from Sierra de Gredos and Serra da Estrela, with straight internal faces, topped by the bluntly toothed projection. Female genitalia somewhat variable in shape, and extent of setal development, but gonocoxae always appearing heavily setose at apex.

Distribution. Mountains of the Iberian Sistema Central (Gredos, Guadarrama, Peña de Francia, Estrela), northern Portugal and Galicia ( Fig. 8 ). In all these areas the species is broadly sympatric with S. epipleuricus , although the two taxa have not been found together in the same localities. In the Sierra de Gredos and Serra da Estrela, known S. rebeccae sp. n. localities appear to be at higher altitude (> 1,000 m) than those occupied by S. epipleuricus , although further work is required to establish whether this is a general pattern. In more northern areas (Galicia), S. rebeccae also occurs at lower altitudes.

Etymology. Named after my wife Rebecca, who has assisted in the collection of this, and numerous other water beetles. The specific epithet is a noun in the genitive case.

Ecology. The new species is found in swift flowing, generally first or second order streams, in mountainous and hill country. Localities typically have a granitic substrate with a mix of gravel and large boulders, and some organic silt. The species is most abundant in small pools below riffles, particularly under overhanging banks or boulders. In the type locality ( Fig. 10 ) it shares this microhabitat with Deronectes wewalkai Fery & Fresneda, 1988 , and Oreodytes davisii rhianae Carr, 2001 .

Comparative notes. Stictonectes rebeccae sp. n. most closely resembles S. epipleuricus and S. occidentalis , both externally and in the form of its male and female genitalia. From these two species, only males can be unequivocally distinguished, by the form of the parameres, which have characteristic apices when seen in lateral view ( Fig. 6 ). The dorsal punctation of the three species is similar, but subtly different (see Figs 2–4 ). In comparison to S. epipleuricus , the large punctures of S. occidentalis are smaller and sparser on both the pronotum and the elytral disc ( Fig. 4 ). The size and density of large punctures in S. rebeccae sp. n. are intermediate between those of these two species ( Fig. 4 ). On the ventral surface, the setose punctures of S. occidentalis are smaller, shallower and sparser than those in S. epipleuricus , which also has a more strongly developed granular sculpture. The large punctures of the elytral epipleura are more obvious in S. epipleuricus than in S. occidentalis . The ventral sculpture of S. rebeccae most closely resembles that of S. epipleuricus , but is slightly less developed than in this species.

Figures

FIGURE 1. Habitus of Stictonectes species. A – C Stictonectes rebeccae sp. n. A) male, Sierra de Gredos (holotype, NMW); B) female Sierra de Gredos (paratype, CDTB); C) male Serra do Estrela (paratype, DNA voucher MNCN-AC 17, IBE). D) Stictonectes epipleuricus male, Sierra de Algibe; E) Stictonectes occidentalis male, Baixo Alentejo, Serra do Cercal.

FIGURE 2. Surface sculpture of Stictonectes species. A) Stictonectes rebeccae sp. n. head; B) – D) pronotum of: B) S. rebeccae; C) S. epipleuricus; D) S. occidentalis.

FIGURE 3. A) Stictonectes rebeccae sp. n. forebody; B) – D) elytral shoulder of: B) S. rebeccae; C) S. epipleuricus; D) S. occidentalis.

FIGURE 4.. Elytral sculpture of: A) Stictonectes rebeccae sp. n.; B) S. epipleuricus; C) S. occidentalis.

FIGURE 5. Male genitalia of Stictonectes rebeccae sp. n. A) penis in dorsal and lateral views; B) paramere.

FIGURE 6. Detail of paramere apex in Stictonectes species. A) Stictonectes rebeccae sp. n. locus typicus; B) Stictonectes occidentalis Portugal, Baixo Alentejo, Serra do Cercal; C) Stictonectes epipleuricus Spain, Malaga, Sierra de las Nieves.

FIGURE 7. Female genitalia of Stictonectes rebeccae sp. n. A) gonocoxosternum; B) gonocoxa with detail of apex.

FIGURE 8. Distribution of Stictonectes rebeccae sp. n. (red circles), S. epipleuricus (green circles) and S. occidentalis (blue circles). Data on S. epipleuricus and S. occidentalis from ESACIB, a database of records of Iberian water beetles (Sánchez- Fernández et al. 2008). In the case of S. epipleuricus, larger, light green circles indicate specimens of S. epipleuricus whose identity has been confirmed by reference to male genitalia during this study. Smaller, dark green circles represent unconfirmed records of S. epipleuricus present in the ESACIB database of Iberian water beetles (cf. notes in text).

FIGURE 10. Type locality of Stictonectes rebeccae sp. n., Spain, Avila, Sierra de Gredos, Río Barbellido below ‘ La Plataforma’, above Hoyos del Espino, ca. 1750 m. Photo D. T. Bilton.