Ischnura praematura Sanmartín-Villar & Lorenzo-Carballa & Zhang & Cordero-Rivera 2022, sp. nov.
Creators: name: Sanmartín-Villar, Iago
name: Lorenzo-Carballa, M. Olalla
name: Zhang, Haomiao
name: Cordero-Rivera, Adolfo
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Odonata
Coenagrionidae
Ischnura
Ischnura praematura

description: Ischnura praematura sp. nov. Sanmartín-Villar & Zhang
Figures 2–4
Holotype. ♂ (currently at ECOEVO Lab, to be deposited at Kunming Natural History Museum of Zoology, ACR- 3521), China, Yunnan, Lijiang, 26º31´03.54”N, 100º13’38.89”E, 2396 m, 04.vii.2015, I. Sanmartín-Villar & H. Zhang leg.; Figure 2a).
Paratypes. 4 ♂♂ (ECOEVO Lab, ACR-3517, ACR-3520, ACR-3522, ACR-3523) and 4 ♀♀ (ECOEVO Lab, ACR-3515, ACR-3516, ACR-3518, ACR-3519). Same collection data as the holotype. 1♂ and 1♀ (Xiaohexiang village, Kunming city, Yunnan province, 04. Vi. 2021, Haomiao Zhang leg; 15.vi.2014, Sanjiacun, Dali city, Yunnan province, Haomiao Zhang leg).
Allotype. ♀ (ECOEVO Lab, ACR-3514; Figure 2b). Same collection data as the holotype.
Etymology. Specific name praematura (i.e. premature: occurring before a state of readiness or maturity has arrived) in reference to its reproductive behaviour, in which mature males mate with newly emerged females before they reach sexual maturity (see below).
Description of holotype
Head (Figure 3a–b). Mainly yellow-green except for some black colouration present on the upper border of the labrum (arrow-like mark), the postclypeus and the upper part of the epicranium. Antennae completely black, except for the yellow-green basal segment. Postocular spots, which are small and rounded, and occipital bar (a central line with one spot at each side) also yellow-green.
Thorax (Figure 2a). Dorsal part of the pronotum’s middle lobe black with one yellow-green spot at each side. Propleuron yellow-green. The posterior lobe of the pronotum shows an elevated central notch, like a saddle cantle. The mesostigmal plate possesses four dorso-lateral triangular protuberances pointing to the sides (Figures 6a, 8a). The dorsal pair of these protuberances are dorsally projected and possess a hook-shaped apical expansion that points laterally, outwards from the body. The lateral protuberances are triangular in shape, and point also laterally outwards from the body. Thorax is mainly yellow-green, except for the blackish middorsal carina, a broader line covering the humeral suture expanded towards the mesepisternum (first segment) and mesepimeron (second segment), a spot at the posterior region of the interpleural suture, and a narrow lateral suture enlarged at the posterior region in the junction between the metepisternum and metepimeron.
Legs (Figure 2a). All parts yellow-green except dorsally black in femur, tibia and the tip of the third tarsal segment. Black colour narrows in the distal part of femur and is not present in the distal part of the tibia.
Wings (Figures 2a, 3c). Hyaline. Nine postnodal veins. Pterostigma bicolour, blurring between blackish (anterior) towards light brown (posterior). Colours more differentiated in hindwings than forewings.
Abdomen (Figure 2a). S1 and S2 black dorsally, greenish and yellow-reddish in the lateral and ventral region respectively. S3 to S5 completely yellow-reddish except for black intersegment areas. S6 mostly yellow-reddish, and black in the 1/5 posterior part. S7 dorsally black and ventrally green-yellow (Figure 2a). S8 with blue colour describing a lower case omega (ω, considering lateral plus dorsal view; Figures 4a, i). S9 blue. S10 blue, with a basal black delta-shaped mark and two triangular anterior black marks. Protuberance in S10 not elevated and dorsally blue.
Genital ligula (Figure 5). Close to the junction with the second segment, the first ligula segment presents a triangular spot of short spines at the basis and a group of long spines at the middle. Second segment with a pair of curved long spines and a pair of C-shape long and wide flagella. The ventral region of the flagella is covered by short spines aligned in rows.
Anal appendages (Figures 4a, b, i). In lateral view (Figure 4a), the dorsal part of the cerci is darker and elongated forming an upwards directed spine. Paraprocts are small and do not extend beyond the cerci. In posterior view (Figure 4b), the spines of the cerci are divergent, whereas the tip of the paraprocts are convergent.
Body length = 24.9 mm; abdominal length = 19.0 mm; hindwing length = 13.8 mm.
Description of allotype. Similar colour patterns and shape as males in head, legs and wings, but turquoise green instead yellow-green (Figure 2b).
The posterior lobe of the pronotum shows a discontinuous notch, only present in the lateral regions (Figures 6b, 7b). Mesostigmal plates do not show developed dorsal protuberances as in males (Figure 8b).
Abdomen (Figures 2b, 4j). Dorsally black and ventrally green. Without vulvar spine. Genital valves overpass the base of the cerci but the stylus does not reach the tip of the cerci. Cerci longer than S10 and are narrow at the tip.
Body length = 25.4 mm; abdominal length = 19.2 mm; hindwing length = 14.9 mm.
Variations in paratypes. There is slight variation in the number of wing veins (up to two additional veins in all wing rows). The blue colouration of male S10 is laterally interrupted by black spots in some specimens, so that they show a blue dorsal dot and a pair of blue lateral regions. No polychromatism was observed and all females showed a greenish colouration pattern different than males (gynochrome). Older individuals develop a grey wax over the cuticle (pruinescence; Figure 10B).
Differential diagnosis. Similar at naked eye in size and colouration to I. aurora and I. rubilio, I. praematura can be distinguished from these two species by the first thoracic segments in males and females and by the anal appendages and the abdominal colouration in males. The elevated central notch that appears in the posterior lobe of the pronotum of I. praematura (Figure 6a, 8a), is not found in I. aurora (Figure 6c, 8c) and I. rubilio (Figures 6e, 8e). The middle part of the posterior lobe is not expanded in I. praematura (males: Figures 6a, 7a; females: Figures 6b, 7b) as it occurs in the other two species (I. aurora males: Figures 6c, 7c; females: Figures 6d, 7d; I. rubilio males: Figures 6e, 7e; females: Figures 6f, 7f). The dorsal protuberances on the mesostigmal plates are triangular with apical expansion in I. praematura (Figures 6a, 8a), while in I. aurora (Figures 6c, 8c) and I. rubilio (Figures 6e, 7e) these are rounded and their basis are narrower. Female mesostigmal plates are wider in I. praematura (Figure 8b) than in the other cited species (Figures 8d, f). All observed male specimens of I. praematura possess no elevated dorsal tubercule in the abdominal S10 (Figures 4a, b), while this structure is highly prominent in I. aurora (Figures 4c, d) and I. rubilio (Figures 4e, f). The superior part of the I. praematura cerci is expanded in a long spine differentiated from the basis (Figures 4a, b), in opposition to the continuous shape in I. aurora (Figures 4c, d) and I. rubilio (Figures 4 e, f). Paraprocts are separated from cerci in I. aurora (Figure 4c) and I. rubilio (Figure 4e), while in I. praematura the paraprocts are wider and they appear, in a lateral view, masked by the cerci (Figure 4a). Ischnura praematura is the only of these three species that shows blue colouration on the dorsal part of the abdominal S10 (Figure 4i).
At naked eye, I. asiatica differs from I. praematura in its abdominal colouration (black and green-yellow with only S9 dorsally blue) and larger body size (body length = 27.5 mm; hindwing = 14.2 mm). However, males of I. praematura and I. asiatica are similar in the first thoracic segments and in the anal appendages, and clearly different from I. aurora or I. rubilio. Ischnura asiatica also possess an elevated central notch in the posterior lobe of the pronotum (Figure 6g), although it is not interrupted in the middle (Figure 7g; also in females; Figure 7h) as in I. praematura (male: Figure 7a; female: Figure 7b). The middle part of the posterior lobe is not expanded as in I. praematura (Figure 6g, 7g), but I. asiatica shows two triangular lateral expansions (Figure 7g; also present in females; Figure 7h) not found in I. praematura. The dorsal protuberances on the mesostigmal plates are triangular with apical expansion in I. praematura and I. asiatica, but they are wider in the former. Female mesostigmal plates are narrower in I. asiatica (Figure 8h). The dorsal tubercle is more elevated in I. asiatica than in I. praematura, and is dorsally blue in both species. The superior part of the I. asiatica cerci is expanded but not developing a long spine as in I. praematura. Paraprocts are narrow and laterally separated from cerci in I. asiatica in contrast with I. praematura. Blue colouration is restricted to the dorsal tubercle in I. asiatica S10.
Phylogenetic relationships with other Ischnura species. Obtained sequences were all identified by BLAST as similar to other odonate species in the NCBI databases. Results of phylogenetic analyses were congruent for both mitochondrial and nuclear datasets, and also for BI and ML analyses. All the Ischnura specimens collected at Lijiang formed a monophyletic and well supported clade (Figure 9), with I. asiatica, I. ezoin (Asahina, 1952) and I. pumilio as the most closely related species. Interestingly, two individuals identified as Ischnura sp., whose sequences were downloaded from GenBank (see Table 1 and Figure 9), clustered together with the specimens from Lijiang sequenced by us, indicating that they are indeed the same species. The author of these sequences, Dr. Ryo Futahashi has confirmed us that these specimens were collected in Xishan District, Kunming, also in the province of Yunnan, ca. 500 km far from Lijiang (R. Futahashi, personal communication, 2 June 2021).
Genetic distances were congruent with the obtained phylogenetic results and generally high between the species included in the analysis (Table 2). For the mtDNA, genetic distances between I. praematura and the rest of the Ischnura species ranged between 11.23% for the I. praematura / I. asiatica pair and 16.67% for I. praematura / I. ramburii (Selys, 1850). For the nDNA genetic distances were lower than for mtDNA. Genetic distances for the ITS marker between I. praematura and other Ischnura species included in the study ranged from 2.58% for the I. praematura / I. ezoin pair to 8.58% for I. praematura / I. senegalensis (see Table 2).
Despite their apparent morphological similarities, I. aurora and I. praematura fall within two distinct genetic clades. Even if we were not able to include I. rubilio in the genetic analyses carried out for the present study, given the high morphological similarity of this species with I. aurora, we would expect I. rubilio to be more genetically similar to I. aurora than to I. praematura.
Ecological and behavioural observations. The Lijiang I. praematura population showed high density and a balanced sex ratio (167 mature males and 170 mature females captured in 10 minutes by one person). Only three immature males and four immature females were observed during mark and recapture. Mature males (Figure 10a) were observed in tandem with both mature and teneral females (see a tandem with teneral female in Figure 10c). While in tandem, males tried to pull females from the substrate with their legs. Mature females in tandem rejected the male mating attempts shaking all body parts and keeping their abdomen in a straight position without touching the male’s secondary genitalia (see Robertson & Tennessen 1984). Despite the high density of the population, we did not record any mating involving mature females, but we detected two matings involving mature males and teneral females (Figure 10d). To our knowledge, mating by teneral females has only been reported in I. aurora from Oceanian populations (Rowe 1978, 2010), while this behaviour is not present in Indian I. aurora (Srivastava & Babu 1984).
description: Published as part of Sanmartín-Villar, Iago, Lorenzo-Carballa, M. Olalla, Zhang, Haomiao & Cordero-Rivera, Adolfo, 2022, Ischnura praematura sp. nov. (Odonata: Zygoptera: Coenagrionidae): a species from Yunnan (China) whose females mate in the teneral state, pp. 59-74 in Zootaxa 5087 (1) on pages 63-69, DOI: 10.11646/zootaxa.5087.1.3, http://zenodo.org/record/5819681