Research Article |
Corresponding author: Ionuţ Ştefan Iorgu ( nusi81@yahoo.com ) Academic editor: Fernando Montealegre-Z
© 2017 Ionuţ Ştefan Iorgu, Elena Iulia Iorgu, Gergely Szövényi, Kirill Márk Orci.
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:
Iorgu IŞ, Iorgu EI, Szövényi G, Orci KM (2017) A new, morphologically cryptic bush-cricket discovered on the basis of its song in the Carpathian Mountains (Insecta, Orthoptera, Tettigoniidae). ZooKeys 680: 57-72. https://doi.org/10.3897/zookeys.680.12835
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A new, morphologically cryptic species of phaneropterine bush-crickets is described from the grasslands of the Romanian Eastern Carpathians. Despite the morphological and acoustic similarities with the recently described Isophya nagyi Szövényi, Puskás & Orci, I. bucovinensis sp. n. is characterized by a peculiar male calling song, with faster syllable repetition rate (160–220 syllables per minute, at 22–27°C) and less complex syllable structure (composed of only two elements instead of three observable in I. nagyi). The morphological description of the new species is supplemented with an oscillographic and spectrographic analysis of the male calling song and male–female pair-forming acoustic duet. An acoustic signal-based identification key is provided for all the presently known species of the Isophya camptoxypha species group, including the new species.
Bioacoustics, Carpathians, Isophya , new species, taxonomy
The glaciers of the Quaternary ice ages shaped distribution patterns in biodiversity and are considered as one of the primary forces of population divergence and speciation (
Although the species-level identification of specimens in this species-group is difficult due to morphological uniformity, the oscillographic structure of male calling songs shows clear differences between species (
During the first visit in Călimani Mountains in the summer of 2012, several Isophya specimens were collected by visual examination of the subalpine vegetation in meadows below Pietrosul Peak (1800–1900 m asl) and at lower altitudes, near the village Gura Haitii (900–1000 m asl). These specimens turned out to be very different from all other known Isophya species regarding the pattern of male calling song and are described here as a new, cryptic species: Isophya bucovinensis sp. n. Later, we discovered this insect at other highland locations in the northern and western areas of the large volcanic caldera of Călimani Mountains and also in Suhard Mountains, in the south-western and western parts of Bucovina region.
The description of examined morphometric characters follows
Photos were taken with a Canon EOS 6D DSLR camera, Canon EF 180 mm f3.5L 1:1 and Canon MP–E 65 mm f2.8 5:1 macro lenses. Scanning Electron Microscope photos were taken of the stridulatory files and male cerci.
The calling song of eleven males and the “mate searching” duet of four males and five females were recorded and analyzed. Recordings were taken with an Edirol R–09HR digital recorder (microphone frequency response 20–40000 Hz, sampling rate of 96000 Hz, 24–bit amplitude resolution). The sound analyses were run using the software Audacity 2.1.2.
The acoustic terminology follows
Romania, Eastern Carpathian Mountains, Călimani Mountains.
Holotype: male. Original label: “Romania, Suceava County, Călimani Mountains, 12 Apostoli Peak, 47.221233°N, 25.213896°E, alt. 1730 m asl, 2015.07.27, leg. I. Ș. Iorgu”, coll. “Grigore Antipa” National Museum of Natural History, Bucharest, Romania. Paratypes: 1 ♂ 1 ♀, labeled: “Romania, Suceava County, Gura Haitii, 47.226236°N, 25.300690°E, alt. 990 m asl, 2012.06.21, leg. I. Ș. Iorgu”; 2 ♂♂ 2 ♀♀, labeled: “Romania, Suceava County, Călimani Mountains, meadow below Pietrosul Peak, 47.130767°N, 25.191679°E, alt. 1800 m asl, 2012.07.20, leg. I. Ș. Iorgu”; 1 ♂ 1 ♀, labeled: “Romania, Suceava County, Suhard Mountains, Omu Peak, 47.507519°N, 25.090278°E, alt. 1860 m asl, 2013.07.21, leg. I. Ș. Iorgu”; 2 ♂♂ 2 ♀♀, labeled: “Romania, Suceava County, Călimani Mountains, 12 Apostoli Peak, 47.221233°N, 25.213896°E, alt. 1730 m asl, 2015.07.27, leg. I. Ș. Iorgu”; 2 ♀♀, labeled: “Romania, Suceava County, Călimani Mountains, 12 Apostoli Peak, 47.222835°N, 25.212571°E, alt. 1730 m asl, 2016.09.03, leg. I. Ș. Iorgu”, all in coll. “Grigore Antipa” National Museum of Natural History, Bucharest, Romania; 3 ♂♂ 3 ♀♀, labeled: “Romania, Suceava County, Călimani Mountains, 12 Apostoli Peak, 47.221233°N, 25.213896°E, alt. 1730 m asl, 2015.07.27, leg. I. Ș. Iorgu”, coll. Hungarian Natural History Museum, Budapest, Hungary.
Audio recordings: 1 ♂, Gura Haitii, 2012.06.21 (air temperature 25°C); 1 ♂, meadow below Pietrosul Peak, Călimani Mts., 2012.07.20 (22°C); 2 ♂♂ 3 ♀♀, meadow below Pietrosul Peak, Călimani Mts., 2012.07.20 (27°C); 3 ♂♂, Omu Peak, Suhard Mts., 2013.07.21 (25°C); 4 ♂♂ 2 ♀♀, 12 Apostoli Peak, Călimani Mts., 2015.07.27 (24°C).
Isophya bucovinensis sp. n.: 1 ♂ 1 ♀, Romania, Suceava County, Călimani Mountains, 47.208928°N, 25.200489°E, alt. 1640 m asl, 2015.07.27, leg. I. Ș. Iorgu; 2 ♂♂ 3 ♀♀, Romania, Suceava County, Călimani Mountains, 47.202448°N, 25.197817°E, alt. 1620 m asl, 2015.07.28, leg. I. Ș. Iorgu; 1 ♂ 4 ♀♀, Romania, Suceava County, Călimani Mountains, 47.134651°N, 25.178858°E, alt. 1680 m asl, 2016.08.07, leg. I. Ș. Iorgu. Isophya nagyi: 10 ♂♂ 2 ♀♀ (audio recorded at 21.2–24°C), Romania, Suceava County, Călimani Mountains, 47.137°N, 25.256°E, alt. 1340 m asl and 47.141°N, 25.267°E, alt. 1580 m asl, 2011.07.27, leg. K. M. Orci, G. Puskás & G. Szövényi.
Fastigium verticis approximately half as wide as scapus, male elytra short and narrow, slightly shorter than or as long as pronotum, reaching anterior part of second abdominal tergite. Length of cubital vein 3/4 of the width of pronotum posterior margin, forming an obtuse angle of nearly 110° at the right margin of left tegmen. The stridulatory file is 2.2–2.5 mm long and contains 105–130 pegs. Male cerci slender, 2.4–2.7 mm long, gradually and moderately incurved in distal 1/4, tapering in an apical denticle. Ovipositor short, upcurved, 8.3–9.2 mm long. Male calling song consists of a long sequence of two-component syllables (Fig.
Morphologically, Isophya bucovinensis sp. n. belongs to the Isophya camptoxypha species group. Within this complex, I. bucovinensis sp. n. and I. nagyi differ from all the other species in the relatively high number of pegs observable in the male stridulatory file. Furthermore, Isophya bucovinensis sp. n. can be easily distinguished from I. nagyi by examining the number of impulse groups within a syllable (three in I. nagyi vs. two in I. bucovinensis sp. n.) and the syllable repetition rate during continuous singing: 60–80 syllables/minute in I. nagyi (21–24°C) and 160–220 in I. bucovinensis sp. n. (22–27°C) (Fig.
Male (Fig.
Photographs of the typical eidonomy of Isophya bucovinensis sp. n. male (A, C, H, J, K) and female (B, D, E, F, G, I). A, B head, pronotum and tegmina in dorsal view C D head, pronotum and tegmina in lateral view E ovipositor in lateral view F female subgenital plate G female cerci in dorsal view H male stridulatory file (SEM) I female stridulatory bristles (SEM) J male cercus (SEM) K male cerci in dorsal view. Scale bars 1 mm.
Morphometric characters measured in males of Isophya bucovinensis sp. n. (N = 10) and I. nagyi (N = 20) (values in millimeters).
Morphometric parameters | Isophya bucovinensis sp. n. | Isophya nagyi | ||||
---|---|---|---|---|---|---|
Min | Max | Mean ± SD | Min | Max | Mean ± SD | |
Width of head | 3.1 | 3.7 | 3.37 ± 0.213 | 3.4 | 3.8 | 3.64 ± 0.105 |
Length of pronotum | 3.8 | 4.3 | 4.02 ± 0.198 | 3.3 | 4.3 | 3.84 ± 0.261 |
Frontal width of pronotum | 3.2 | 3.4 | 3.32 ± 0.083 | 3 | 3.6 | 3.19 ± 0.159 |
Caudal width of pronotum | 3.9 | 5.0 | 4.41 ± 0.442 | 4.4 | 5.2 | 4.6 ± 0.201 |
Length of left tegmina | 3.4 | 4.8 | 3.88 ± 0.449 | 4 | 4.8 | 4.44 ± 0.211 |
Width of left tegmina | 3.1 | 4.2 | 3.7 ± 0.361 | 3.8 | 4.4 | 4.1 ± 0.16 |
Length of hind femur | 13.5 | 15.9 | 14.7 ± 0.718 | 14.3 | 16.8 | 15.58 ± 0.747 |
Length of cercus | 2.4 | 2.7 | 2.5 ± 0.103 | 2.2 | 2.8 | 2.54 ± 0.131 |
Coloration green, densely punctuated with fine, dark green and brown spots. Some specimens with two dorsal, parallel, bilateral stripes from pronotum to end of abdomen, red, orange, or yellow colored. Antennae greenish, reddish or brownish, compound eyes bicolored: upper part brown or red and lower part green. Disc of pronotum green, bordered by a yellowish or whitish band, from behind the eye to the posterolateral angle of wing, complemented by a reddish brown stripe in metazona. Tegmina brown or dark red, with green margins and greenish or yellowish white costal margin, as continuation of pronotum band. Legs usually green, brownish or reddish. Cerci brown or reddish brown.
Female (Fig.
Body coloration similar to that of male. Tegmina green with brownish inner and whitish or yellowish lateral edges. Ovipositor green with dark brown spines.
(Figs
Descriptive statistics for oscillographic parameters of the male calling song and for female response delay in Isophya bucovinensis sp. n. and I. nagyi (duration values in milliseconds). Number of specimens for which measurements were made: I. bucovinensis 11 males, 5 females; I. nagyi 10 males, 2 females.
Calling song parameters | Isophya bucovinensis sp. n. | Isophya nagyi | ||||
---|---|---|---|---|---|---|
Min | Max | Mean ± SD | Min | Max | Mean ± SD | |
Duration of syllable (DS) | 237 | 385 | 311.6 ± 57.85 | 489.6 | 934.3 | 727.33 ± 148.27 |
Duration of “B”–element (DB) | 156 | 286 | 215.2 ± 52.7 | 129.5 | 217.8 | 188.96 ± 32.03 |
Number of impulses in “B”–element (NIB) | 46 | 79 | 60.1 ± 11.54 | 38.7 | 79 | 56.83 ± 12.77 |
Silent interval between “B”– and “C”–elements (IntBC) | 59 | 94 | 76.85 ± 10.56 | 54.2 | 91.5 | 69.43 ± 12.36 |
Duration of “C”–element (DC) | 3 | 28 | 16.45 ± 7.39 | 1 | 5.4 | 3.59 ± 1.62 |
Number of impulses in “C”–element (NIC) | 2 | 7 | 4.4 ± 1.64 | 1 | 4 | 2.6 ± 0.96 |
Silent interval between successive syllables (IntS) | 76 | 125 | 94.2 ± 17 | 121.2 | 227.9 | 160.24 ± 34.24 |
Female response delay (F) | 48 | 66 | 58.7 ± 4.77 | 71 | 127 | 112.2 |
Females find males by phonotaxis and emit simple clicks if the male song is attractive for them. In the resulting male–female acoustic duet, the female replies only after the male syllables (“C”–part), with a latency of 48–66 ms (mean ± SD: 58.7 ± 4.77 ms, n = 200 replies from 5 females) (Fig.
Acoustic signals analysis in two close–related species: A, B oscillographic pattern of male calling song C, D a detailed syllable and the female response (marked with green) E spectrum (function: Hanning window, size: 512). A, C, E red line Isophya bucovinensis sp. n. B, D, E blue line Isophya nagyi.
The specific name is derived from the historical region of Bucovina, “Land of the beech forests”.
The new species populates mesophytic montane meadows in the south–western part of Bucovina, within the altitudinal range of 900–1900 m (Fig.
Isophya bucovinensis sp. n. is known only from Călimani and Suhard Mountains. It could be considered as Endangered B1ab(iii, v)+2ab(iii, v) following IUCN’s Red List categories and criteria version 3.1 (known EOO=234 km2 and AOO=28 km2; the constant degradation of species’ habitat is the result of mechanized mowing in June and July, and overgrazing, especially in Suhard highlands) (
In this study, we report the discovery and give the description of a new bush-cricket species recognized based on its distinctive calling song. The basic pattern of its song is not unique within the genus Isophya: a series of evenly repeated syllables, each consisting of two elements: a longer impulse series followed by a short impulse group (see e. g.
Since the species of the Isophya camptoxypha species-group are all very similar to each other regarding the morphology, we believe that a male calling song based identification key will be helpful to identify specimens from populations of unknown species identity.
Identification key for the presently recognized species of I. camptoxypha species group, based on male song characters:
1 | Male calling song consists of syllable groups separated from each other by a characteristic interval. Syllable groups are composed of two syllable types (“A” and “B”), each group being a series of “A” syllables followed by one “B” syllable containing conspicuous, high amplitude clicks (Fig. |
2 |
– | Male calling song is a series of syllables, no regular syllable groups are observable, syllables show the same basic structure (i.e. the song is composed of one syllable type) (Fig. |
3 |
2 | “A” syllables are shorter than 25 ms, the conspicuous click(s) follow(s) a silent interval of 300–450 ms (Fig. |
I. posthumoidalis |
– | “A” syllables have a duration of 30–60 ms, the high amplitude click(s) between the syllable groups follow(s) a 550–950 ms long silent interval (Fig. |
I. dochia |
3 | The longest impulse series in the syllables (LIS) is shorter than 80 ms | 4 |
– | LIS is longer than 100 ms | 5 |
4 |
LIS falls between 25–60 ms, consisting of more than 10 impulses (Fig. |
I. camptoxypha |
– |
LIS is shorter than 25 ms, consisting of 1–3 impulse(s) (Fig. |
I. sicula |
5 | Syllables consisting of two impulse groups | 6 |
– | Syllables consisting of three impulse groups (Fig. |
I. nagyi |
6 | Interval after LIS is longer than 300 ms (Fig. |
I. ciucasi |
– | Interval after LIS is shorter than 150 ms (Fig. |
I. bucovinensis sp. n. |
Oscillograms showing the typical pattern of male calling songs in each species of the Isophya camptoxypha species-group: A I. posthumoidalis (25°C, Bieszczady Mountains, Poland) B I. dochia (24.8°C, Gurghiu Mountains, Romania) C I. camptoxypha (25°C, Bieszczady Mountains, Poland) D I. sicula (24.8°C, Harghita-Ciceu Mountains, Romania) E I. ciucasi (25°C, Ciucaș Mountains, Romania) F I. nagyi (22.5°C, Călimani Mountains, Romania) G I. bucovinensis sp. n. (25°C, Suhard Mountains, Romania). Time scale (shown at the bottom) is the same for all oscillograms in the figure. The arrows indicate the characteristic interval separating syllable groups.
The duration values given in the above key are based on male songs recorded at an ambient air temperature between 20–25°C. To identify specimens, a song recording should be made in that range of air temperature. The key is most reliable when mean values based on at least 5–10 measurements per specimen are used in all quantitative characters.
The easiest way to identify male specimens of Isophya bucovinensis sp. n. is to examine both the male stridulatory file and the pattern of male calling song. Within the I. camptoxypha species group, only two species have male stridulatory files containing more than 100 stridulatory pegs: I. nagyi and I. bucovinensis sp. n. Interestingly, except for the different number of syllabic elements and syllable repetition rates, the syllables produced by males of Isophya bucovinensis sp. n. and I. nagyi show remarkable similarities in oscillographic structure (Fig.
In Isophya bucovinensis sp. n., the delay of female response is much shorter (48–66 ms) than that in I. nagyi (71–127 ms) (Fig.
The Isophya camptoxypha species-group shows a surprisingly high rate of endemism in the Eastern Carpathians. Five of its recently described species have very small distribution areas (Fig.
This study was supported by a grant from the Romanian National Authority for Scientific Research and Innovation CNCS – UEFISCDI, project number PN–II–RU–TE–2014–4–2093, awarded to IȘI. The work of KMO and GSz was supported by a grant from the Hungarian National Research Fund (OTKA/NKFI K81929). We want to thank T. Sahlean for preparing the distribution map. The authors acknowledge Călimani National Park Administration for the excellent working conditions and L. Moscaliuc, A. Derscariu, T. Sahlean, V. Gavril, G. Chișamera, L. Fusu, M. Dascălu, O. Popovici and M. Mitroiu for their company on field expeditions. We thank K.-G. Heller and H. Braun for their helpful comments on the manuscript.