Tibicina longisyllaba, Hertach, 2021

Hertach, Thomas, 2021, Look closely and listen carefully: unexpected cicada diversity in northern Sardinia, with the description of a new species (Cicadidae: Tibicina), Zoological Journal of the Linnean Society 191 (3), pp. 823-845 : 833-839

TIBICINA LONGISYLLABA SP. NOV.

LSID: urn:lsid:zoobank.org:act:E06E9415-FC2C-487F-B0BB-696599C53BE4

Type material

The type series consists of 17 males and eight females. It is kept in the Natural History Museum of Bern ( NMBE) (holotype; Fig. 7A, D, E ), the Natural History Museum of Basel ( NHMB) and the private collection of the author.

Holotype male: Verbatim label information: ‘ Italy / SW Tempio Pausania , SARD/ 40.8689° / 9.0227°, 132 m asl / 29.7.2018, leg. Thomas Hertach’ (label rectangular, white, printed) and ‘ Tibicina longisyllaba ♂ /det. T. Hertach 2018/Collection Code no. 27.026 ’ (label rectangular, white, printed) and ‘ HOLOTYPUS ♂ / Tibicina longisyllaba sp. n. Hertach 2020’ (label rectangular, light red with dark red margin, printed).

Paratypes: All paratypes with labels ‘ PARATYPUS XX Y, Tibicina longisyllaba sp. n. Hertach 2020’ (label rectangular, white with red margin, printed) at which ‘XX’ is the number of the paratype and ‘Y’ the sex of the specimen. Paratype males: Monte Pinu , Sardinia, 40.9367° / 9.3933°, 280 m a.s.l., 28.6.2008, leg. T. Hertach (paratype 1) ; N of Ala dei Sardi , Sardinia, 40.6889° / 9.3663°, 560 m a.s.l., 26.7.2013, leg. T. Hertach (paratypes 2 and 3) ; La Licciola , Santa Teresa Gallura, Sardinia, 41.2149° / 9.2608°, 60 m a.s.l., 10.7.2017, leg. T. Hertach (paratype 4) ; above Badesi , Sardinia, 40.9734° / 8.9045°, 280 m a.s.l., 12.7.2017, leg. T. Hertach (paratypes 5 and 6) ; N of Padru , Sardinia, 40.7828° / 9.5146°, 240 m a.s.l., 15.7.2017, leg. T. Hertach (paratype 7) ; Murta Maria, Sardinia, 40.8938° / 9.5926°, 9 m a.s.l., 17.7.2018, leg. T. Hertach (paratype 8) ; Loculi – Lula , Sardinia, 40.3934° / 9.5163°, 51 m a.s.l., 19.7.2018, leg. T. Hertach (paratypes 9, 10 and 11) ; Capo Comino , Sardinia, 40.5321° / 9.8105°, 25 m a.s.l., 21.7.2018, leg. T. Hertach (paratypes 16, 17 and 18) ; Bidderosa, Sardinia, 40.4710° / 9.7761°, 48 m a.s.l., 21.7.2018, leg. T. Hertach (paratype 20) ; Capo Comino , Sardinia, 40.5333° / 9.8067°, 10 m a.s.l., 6.7.2008, leg. T. Hertach (paratype 24). Paratype females: Loculi – Lula , Sardinia, 40.3934° / 9.5163°, 51 m a.s.l., 19.7.2018, leg. T. Hertach (paratypes 12 and 13) ; Cala Gonone , Sardinia, 40.2868° / 9.6357°, 36 m a.s.l., 20.7.2018, leg. T. Hertach (paratype 14) ; above Dorgali , Sardinia, 40.3000° / 9.6344°, 297 m a.s.l., 20.7.2018, leg. T. Hertach (paratype 15) ; Capo Comino , Sardinia, 40.5321° / 9.8105°, 25 m a.s.l., 21.7.2018, leg. T. Hertach (paratype 19) ; Bidderosa, Sardinia, 40.4710° / 9.7761°, 48 m a.s.l., 21.7.2018, leg. T. Hertach (paratypes 21 and 22) ; SW of Tempio Pausania , Sardinia, 40.8689° / 9.0227°, 132 m a.s.l., 29.7.2018, leg. T. Hertach (paratype 23; Fig. 7B ).

Diagnosis

Morphology: There are good and highly significant indicators for T. longisyllaba ( Table 4 ), although I am not able to distinguish all specimens with absolute certainty from T. c. corsica and T. sp. indet.: (1) basal forewing venation up to the node vividly yellow, instead of light ochre as in T. sp. indet. and many T. c. corsica ( Fig. 4 ); (2) submedian sigilla on mesonotum less hairy than in T. sp. indet. and T. c. corsica (often below 20% hair cover; Fig. 5 ); (3) black portion of sternites IV to VI on abdomen shining through hairs normally larger than 20%, while often smaller in T. sp. indet. and T. c. corsica ( Fig. 5 ); (4) males: short timbal rib number on average higher, normally 10; (5) males: body length to timbal width ratio in mean lower (11.1 ± 0.4).

Tibicina nigronervosa can be distinguished by the dark basal forewing venation ( Fig. 7G ), only 7.0 ± 0.5 (maximally 8) short ribs at the timbals and a high body length to timbal width ratio (12.8 ± 0.5). Furthermore, lateral light spots on the pronotum do not exist and rear cuneiform spots on the mesonotum are normally isolated from the lateral band. Habitus and coloration of T. longisyllaba are also reminiscent of Tibicina garricola Boulard, 1983 occurring on the mainland in France and the Iberian Peninsula, but the more trapezoid pronotum with prominent collar carries light (orange-reddish-brownish) fasciae in T. garricola . Lateral yellow patterns at the mesonotum are reduced, ending in a total of normally eight scutal spots. The shape of the genitalia is different with: uncus in lateral view dorsally more rounded, and ventrally strongly emarginate toward the tip; theca with relatively long and dangling lateral lobes; vesica considerably broadened in upwards curve ( Boulard, 1983; Quartau et al., 2001; Stéphane Puissant, pers. comm.).

Acoustics ( Figs 2 , 3 ; Table 3; Supporting Information, Appendix S4): The loud, buzzing calling song of T. longisyllaba is strident and fibrillations are clearly audible, while in T. sp. indet. and T. nigronervosa no structure is audible in the song, and in T. c. corsica it is less distinct. Syllable periods are long (19.6 ± 0.6 ms) with no overlaps of measured extrema among Corso- Sardinian species. Centre frequency is significantly lower than in all other Tibicina taxa from Sardinian populations (Wilcoxon–Mann–Whitney rank sum test: P <0.001 for T. sp. indet.; P <0.001 for T. c. corsica and P = 0.018 for T. nigronervosa ). However, significant frequency differences are not seen when Corsican specimens are compared to T. longisyllaba (Wilcoxon– Mann–Whitney rank sum test: P = 0.081 for T. c. corsica and P = 0.264 for T. nigronervosa ).

Ecology: Tibicina longisyllaba clearly prefers habitats with a dominance of ligneous plants higher than 40% in comparison to sympatrically occurring T. sp. indet. ( Fig. 6B ; chi-square contingency test for two classes <40%,> 40%; P = 0.001, N loc = 42). Vegetation is normally also taller (chi-square contingency test for the three classes <0.5 m, 0.5–2.0 m,> 2.0 m; P = 0.028, N loc = 42).

Morphological description

Measurements of holotype (for other males of the series and females see Table 5 ): Body length: 24.4 mm, body width (abdomen, tergite II): 9.2 mm, forewing length: 28.8 mm, forewing width: 11.6 mm.

Male holotype with remarks on the variability in the paratype series ( Fig. 7 ): Head: About same width as mesonotum. Black with silvery hairs, small triangular yellow patch on epicranial suture and four marks along the frontal margins of vertex (the latter rarely reduced in paratypes). In dorsal view, vertex laterally next to the postclypeus almost horizontal and forming a conspicuous angle with the postclypeus. Compound eyes in live specimens grey-brown with darker spots. Ocelli orange to brownish, forming an obtuse triangle. Distance between lateral ocelli and next compound eye equal. Antennae blackish with exception of yellow margins of scapes. Postclypeus toward frons angled and ventrally with longitudinal groove, black with silvery hairs, lateral margins and upper central part yellow. Anteclypeus black with frontal margin yellow. Lorum also black with margins yellow, gena with prominent yellow margin. Rostrum scarcely reaching mid trochanter, labrum yellowish to brownish, mentum with longitudinal brown-yellow drawings, labium dark brown.

Thorax: Pronotum generally relatively loosely haired and black except for a yellow median line, two yellow patches between the paramedian and the lateral fissures toward the pronotal collar, which are fused by a small connection (in paratypes only exceptionally fused, 6%, and sometimes completely missing, 25%). Pronotal collar large and yellow, its lateral angles pronounced and rounded with a considerable portion of dark colour, margin frontal to the lateral angles slightly S-shaped in dorsal view. Scutum generally black and with characteristic markings ( Figs 5 , 7 ; see also: Supporting Information, Appendix S2): (1) both submedian sigilla with a crescent-shaped yellow spot at their posterior bases and (2) starting frontal to the scutal depression a yellow band that forms a frontal corner and then laterally surrounds the lateral sigilla (in paratypes rarely interrupted). Parapsidal suture marked yellowish (in paratypes sometimes missing). From frontal margin with submedian sigilla to scutal depressions almost hairless, laterally and toward the rear more silvery hairs (for intraspecific variability see: Supporting Information, Appendix S2). Cruciform elevation predominantly yellow, its lateral depressions mainly dark. Metanotum centrally visible and yellowish, laterally with darker portions (in some paratypes also centrally with dark patches). On the ventral side, central segments generally darker than lateral segments, which are often light yellow. Opercula small and slender and distant from each other, mainly yellow (in paratypes basal parts often dark brown).

Abdomen: Abdomen inverted U-shaped in crosssection. Tergite I centrally, with undulating posterior margin. Tergites III to VIII black with orange to yellow posterior margins; margins centrally small, laterally more dominant. Tergite II mainly orange to yellowish laterally. Sternites III to VII and epipleurites frontally black and toward the rear orange; maximal black portions at sternites IV to VI, hair cover comparatively thin to almost absent (for intraspecific variability see: Supporting Information, Appendix S3). Sternite VII relatively drawn-out but still broader than long. Sternite VIII barge-like, long and tapered, yellow and black (in paratypes also often completely dark, 48%, or sometimes completely light, 22%). Timbals lacking a cover, with regularly alternating long and short ribs. Ten short ribs present ( Fig. 7E ; in paratypes exceptionally 9, 6%, or 11, 6%). Timbals relatively large, ratio body length to timbal width 10.5 (in paratypes minimum 10.2, maximum 11.8).

Genitalia ( Fig. 7D ): Similar to Tibicina corsica . Pygofer dorsally black, ventrally yellow and almost straight without upper lobes, flattened in cross-section for upper part, at the apex strongly emarginate.Anal styles tonguelike to drop-shaped. In lateral view, predominantly black and dominant uncus dorsally straight, ventrally convex and slightly emarginate near the tip; in dorsal view concave at the tip. Claspers absent. Theca continuously broadened toward the apex, lateral lobes short. Thin and slightly flattened vesica curved upwards and more or less narrowing subsequently toward the gonopore.

Legs: All legs with dark brown to black longitudinal fasciae on a yellow ground. Front femora with four spines: the first spine isolated, solid sharp and directed upwards, the second spine broad and straight, the third spine tiny and triangular and the forth tiny and thin (in paratypes forth spine often missing), the latter three forming a group. Distance between first and second spines much larger than length of these two main spines. Mid-legs spineless, hind legs with six solitary tibial spurs (paratypes 4 to 7) and tibial comb carrying a dozen spurs. Large meracantha tongue-like, reaching the posterior horizontal extensions of the opercula.

Wings: Forewing hyaline except for smoky to black parts at the basal cell, at the base of the clavus and the pterostigma. Cubitus anterior vein originating approximately at the centre of the basal cell and, therefore, clearly separated from median vein. Eight apical cells. Veins vividly yellow (RGB-values of alive holotype 221/171/58 for basal median vein and 234/190/81 for distal parts of median vein near the node; for intraspecific variation see Fig. 4 ) with the following exceptions: costal vein black (in paratypes rarely also yellowish), including its functional distal prolongation (= subcostal vein), majority of veins forming the apical cells brown to black. Basal junction of anal veins yellow and basal membrane orange. Hindwing transparent, except for smoky base, margins of jugum and plaga additionally orange to whitish, base of costal cell light orange. Its veins predominantly yellow, but with a tendency to more dingy yellow or brownish parts, basally but especially apically. The ambient vein dark brown to black, as well as the anal veins 2 and 3. Posterior radial and medial veins not fused at their base.

Female paratypes ( Fig. 7B ): On average, shorter body than in males ( Table 5 ). Female body and wing coloration are close to the holotype and paratype males. On the head, two females have the central yellow band of postclypeus prolonged to dorsal part and a minority has yellow spots merged along the frontal margin of vertex. On the thorax, metanotum centrally often orange, rarely with darker portions. Opercula even smaller than in males, sometimes more angled, meracanthus surpasses the caudal extensions of the opercula. On the abdomen, tergite I with normally less undulating posterior margin. Lateral yellow to orange portions reduced at tergite II. Sternite VII with a V- to U-shaped notch to the middle and with a broad orange margin, frontally dark brown to black. Sternites IV to VI often with high portions of black ( Fig. 5 ; Supporting Information, Appendix S3). Ventral parts of tergite IX orange to brownish, dorsal surface black with orange to brownish, progressively narrowing margin. Its dorsal beak black, pointed and long. Ovipositor brown, its sheath black. Ratio of body length to ovipositor length (including sheath) 4.18 ± 0.09. Wings and legs identical to males, the facultative forth spine at forelegs missing.

Acoustic behaviour

Similar to all other European Tibicina , the fundamental element of the T. longisyllaba calling song is a monotonous buzz that normally lasts for several minutes without interruption. The song starts and ends abruptly, and is loud and audible up to a distance of 100 m ( Fig. 2 ). The timbre of the buzz is strident and fibrillations are perceptible for the human auditory system caused by the slow micro rhythm: SYD (syllable duration; 17.1 ± 0.9 ms) are long and ISYD (pauses between the syllables; 2.5 ± 0.8 ms) extraordinarily pronounced, which ends in SYPs of 19.6 ± 0.6 ms (mean of individuals responsible for extrema: 18.5 ms and 20.9 ms). SYP is the best character of the species-specific song pattern ( Fig. 3A ). Long SYDs are a product of two variables: (1) the number of pulses (NP) is at least as high as in T. c. corsica and clearly higher than in T. sp. indet. and T. nigronervosa and (2) the period of pulses (PP) is longer than in all other Corso-Sardinian taxa. ISYD, NP and PP contribute from individual to individual in a variable degree to the specific SYP ( Fig. 3B ; Table 3).

Centre frequency means vary between 8.7 kHz and 10.1 kHz for individuals. Half of the energy was maximally measured in a frequency band from 8.4 to 10.7 kHz (Q1 and Q3 frequencies; Table 3). The frequency domain is probably positively correlated with body length (linear regressions; R 2 = 0.30) and body width (R 2 = 0.20), but the number of specimens with good acoustic recordings and body measurements is still low (N

ind

= 7).

Tibicina longisyllaba has, besides the calling song, an additional repertoire of acoustic signals. Their function has not been completely clarified: courtship, rivalry or alarm. At least one male was recorded during a long sequence of alarm behaviour. In the process, sequences of a few seconds up to 12 seconds were emitted with important amplitude modulations at the end but also in the middle of the sequence. Low-intensity parts were produced by only one timbal, the second was inactivated. High-intensity parts were characterized by a raised abdomen. Hereby, both timbals or only one timbal were working. This behaviour is close to the courtship songs described for the genus by Sueur & Aubin (2004). Males can also produce audible wing-flicks.

Etymology

The species name ‘ longisyllaba’ refers to the acoustic behaviour of the species, from Latin longus, long and syllaba, syllable. Syllable periods of T. longisyllaba break the European genus record so far held by T. steveni (17.4 ± 0.7 ms, N ind = 14; pers. data; Supporting Information, Appendix S4). While general works mention 100 to almost 500 timbal movements per second typical for cicadas worldwide (Burton & Burton, 2002), T. longisyllaba sing with only 51.5 ± 1.5 movements per timbal and second. However, North American Okanagana canadensis (Provancher, 1889) slow down to 24.7 ± 0.9 movements by extremely prolonging the intersyllable durations (ISYP; Chatfield-Taylor & Cole, 2019).

Distribution and ecology

Tibicina longisyllaba is most probably endemic to north-eastern Sardinia, with 22 local populations known until now ( Fig. 8 ). In the north and in the east, the distribution area is limited by the coast, and a distance of 30 km to the sea was never surpassed. Most western local populations are found from north to south in Badesi–Erula–Ala dei Sardi–Lula and Orgosolo. The southern limits are not clear. The known extension from north to south is about 110 km. The elevational range goes from sea level to 560 m a.s.l. (Ala dei Sardi) with almost half of the records below 60 m and only four above 300 m a.s.l.

The distribution area contains many locations with tall shrubland (maquis; Fig. 6E ). It is a rocky region on predominantly crystalline grounds. However, also limestone-influenced habitats are colonized in the Supramonte region. Of the local populations, 60% were found in the most extreme vegetation classes 7 and 8 ( Fig. 6 ). Thus, favourite habitats are woodlands with more than 2-m tall ligneous plants or closed tall shrubland with more than 60% dominance and ligneous plants with a minimal height of 0.5 m. Shrubland is composed of Cistus spp. , Pistacia lentiscus L., Euphorbia spp. and broom species. Populations have become established in some coastal forests with pines ( Pinus spp. ), which are normally planted. The species was occasionally found in gardens of settlements, but populations are normally rather stenoecious. Often T. longisyllaba is the only species in its habitats. In one place it was found syntopic with T. nigronervosa , which colonized the neighbouring forest. In another place it was found syntopic with T. sp. indet. with unclear habitat sharing due to low acoustic activity. In the costal pine forests, T. longisyllaba is associated as a minority with Cicada orni. Population densities of T. longisyllaba are often lower than in T. c. corsica or T. sp. indet.; males seem to occupy larger territories. However, this is not the case in coastal habitats between Siniscola and Orosei where the most important populations have been found.

Figures

Figure 2. Calling song examples of the Tibicina OTUs from northern Sardinia. A, sonograms of LONG and CIST (10-s phrases). B, oscillograms (time vs. amplitude) of four different OTUs (0.5-s phrases, left and 0.1-s phrases, right) with terms marked.

Figure 3. Calling song characters of the Tibicina OTUs from Sardinia and the known species from Corsica. Mean values per individual. A, syllable periods (SYP) vs. centre frequencies (Nind = 103). B, contribution of PP, NP and ISYD to the species-specific SYP (Nind = 103). C, two converse examples of temperature dependency of SYP (Nind = 19 resp. 23).

Figure 4. Morphological trends in the Corso-Sardinian Tibicina OTUs CIST, CORS and LONG (part I). Colour tints of basal and central forewing venation. RGB-values taken at two positions (see numbered ovals in example CIST) from photographs of live individuals. R-values constant for boxes, G-values at vertical axes, B-values at horizontal axes. Size of circles is relative to the measured occurrences (Nind = 95, N max = 12, Nmin = 1). Two typical venation phenotypes of LONG and CIST (right, below). CORS and T. c. corsica are merged for easier illustration.

Figure 5. Morphological trends in the Corso-Sardinian Tibicina OTUs CIST, CORS and LONG (part II). Individual ranks of overall alignments of hair cover of submedian sigilla on mesonotum vs. black portion shining through hairs on sternites IV to VI (see green framed body sectors; Nind = 70). Photographs visualize extreme phenotypes. Individuals were labelled with a random number and sorted twice for each character from photographs of live individuals and alignments differed only by a mean of 4.7 (sigilla) respectively 6.5 rank positions (sternites). Significances were similar and mean ranks of individuals of repeated alignments are shown here. CORS and T. c. corsica are merged for easier illustration.

Figure 6. Habitat specialization of the Tibicina OTUs from northern Sardinia. A, portions of eight vegetation classes in all four Tibicina OTUs from Sardinia. Data are shown per square root of observed individuals (Nind = 586). Foreground drawing after Puissant & Sueur (2001). B, portions of eight vegetation classes in partly sympatrically occurring CIST and LONG. Data is visualized per location and the two class variables are displayed on the axes (dominance of ligneous plants vs. vegetation height; Nloc = 42). Bold numbers are vegetation class numbers and black dashes indicate the number of counts. Example: Vegetation class 3 fits for 8.5 locations in CIST, containing 2.5 locations in sympatry with LONG and 6 locations in allopatry to LONG. Typical Northern Sardinian habitats of: C, CIST (grassland, Pattada); D, CORS (low shrubland, Stintino); E, LONG (tall shrubland, Priatu); F, NIGR (woodland, Rena Majore).

Figure 7. Morphology of Tibicina longisyllaba and relatives. A, holotype male of Tibicina longisyllaba in dorsal view and ventral view of the abdomen from Tempio Pausania (black bar = 1 cm). B, paratype female of Tibicina longisyllaba from Tempio Pausania. C, syntype male of Tibicina cisticola from the Natural History Museum of Berlin with original labels. D, genitalia of T. longisyllaba. Timbals with alternating short and long ribs of (E) T. longisyllaba holotype in comparison to (F) T. cisticola syntype (equal magnification, almost similar body size, 24.4 resp. 24.8 mm; white perpendicular line = timbal width definition). Morphological extremes in natural habitats: G, male of T. nigronervosa; H, male of T. sp. indet.

Figure 8. Distribution of the genus Tibicina in northern Sardinia and southern Corsica. All records are confirmed by song assessments. Large circle: ≥ 30 specimens detected. Medium circle: 6–29 specimens. Small circle: 1–5 specimens.