Morphological variability of Cordulegaster trinacriae in Italy 1st December 2019175 Morphological variability of Cordulegaster trinacriae in Italy (Odonata: Cordulegastridae) Andrea Corso MISC – Via Camastra, 10, 96100 Siracusa, Italy; <[email protected]> Received 15th July 2019; revised and accepted 10th September 2019 Abstract. This paper describes the most helpful features for field identification C.of trinacri­ ae and the relevant morphological variability encountered. In C. trinacriae the yellow frons was without a dark horizontal marking in about 70 % of the sample or showed a barely pat- terned frons, while the remaining 30 % showed a more or less defined dark smudge, though always narrower and less bold than in C. boltonii. The percentage of unmarkedversus marked frons was similar throughout the distributional range of C. trinacriae except in Sicily, where the unmarked yellow frons was much more common (87 %) and in Campania, where in- dividuals with a dark mark on the frons were slightly more common than unmarked ones. In C. trinacriae the occipital triangle was almost always yellow with no or almost no dark markings, cleaner, and purer yellow than in C. boltonii from central Italy. The appendages of C. trinacriae always showed the characteristic form except for a few individuals, which might be hybrids. In C. boltonii they were found to be rather variable, especially on individuals from the southern part of its distributional range in central Italy, where intermediates and hybrids occur. Here, the appendages were sometimes similar (but not identical) to C. trinacriae, and therefore, this character is considered of limited use in the field. Individuals of C. trinacriae can be distinguished in areas of sympatry from intermediate C. boltonii and from hybrids when they show the following characters: i) unmarked yellow frons; ii) bright yellow, almost unmarked occipital triangle; ii) typical deeply notched lower appendages and long, sinuous upper appendages. Further key words. Dragonfly, Anisoptera, frons pattern, occipital triangle, field identifica- tion Introduction Cordulegaster trinacriae Waterston, 1976, is endemic to the southern half of Italy from Sicily to the regions of Lazio and the Abruzzi. The type local- ity is in Sicily, which is reflected by the scientific name; the Greek word trin acria means “three pointed” and is the earliest known name of the island of Sicily, formerly a Greek possession, so named for its triangular Odonatologica 48(3/4) 2019: 175-201Odonatologica – DOI:10.5281/zenodo.3539730 48(3/4) 2019: 175-201 176 A. Corso shape (Boudot et al. 2009; Riservato et al. 2014; Boudot & Kalkman 2015). The species is well differentiated, both morphologically (Boudot & Jacque min 1995; Boudot 2001; Dijkstra & Lewington 2006; Dijkstra & Kalkman 2012; Solano et al. 2018) as well as genetically (Froufe et al. 2014; Solano et al. 2018). Its morphological variability was described, albeit only briefly, by Balestrazzi et al. (1982, 1983), Galletti & Pave- si (1985) and Ottolenghi (1991). On the other hand, Balestrazzi et al. (1983), Galletti & Pavesi (1985), and more recently Terzani (2015, 2016), discussed the morphological variability of Italian populations of Cordulegaster boltonii (Donovan, 1807), with the latter author stressing the need for larger study samples from Lazio and the Abruzzi and especially from the overlapping hybridization zone of the two species (Solano et al. 2018). Concerning other European populations of C. boltonii, the variabil- ity and the validity of the various proposed subspecies have been extensive- ly studied, sometimes erroneously with respect to current knowledge and systematics, by, e.g., St. Quentin (1952), Jurzitza (1965), Waterston (1976), Theischinger (1979), Ocharan (1989), Lohmann (1992), Bou- dot & Jacquemin (1995), Boudot (2001), and Froufe et al. (2014). The morphological variability of the appendages in male C. trinacriae, C. bolto­ nii and their hybrids was recently described by Solano et al. (2018), who did however not discuss any other field identification features. As C. tri­ nacriae is listed in the Habitats Directive (Annex II and IV) and the Bern Convention (Annex II and Revised Annex I), reliable identification in the field is a priority when planning conservation actions and for any monitor- ing projects and research. Given the variability of morphological characters in both species and their similarity, it is important to analyse the reliability of the different characters to assign individuals to a respective species and to identify the features most helpful for field identification of C. trinacriae. The objective of the present paper is to analyse the morphological traits that are most helpful to distinguish C. trinacriae from C. boltonii and their hybrids in the field. The following characters are considered: the colour pattern of the frons, the colour of the occipital triangle, the pattern of the abdomen, and the form of the appendages. For comparison, data on the variability of C. boltonii from Lazio and Tuscany − the populations near- est to populations of C. trinacriae − are provided, with a brief overview of Odonatologica 48(3/4) 2019: 175-201 Morphological variability of Cordulegaster trinacriae in Italy 177 specimens from northern Italy as well. Also, considerations are given on the hybridization between the two species, which covers an extensive area (Solano et al. 2018). Material and methods In order to study the morphological variability of Cordulegaster trinacriae, 355 specimens were studied: 317 males and 38 females (Fig. 1; Tables 1, 2). The specimens were assorted according to their regions of origin; 121 were from Sicily (102♂, 19♀), 88 from the Abruzzi (78♂, 10♀), 35 from Molise (33♂, 2♀), 45 (41♂, 4♀) from Campania, and 66 (63♂, 3♀) from Calabria (Fig. 1; Tables 1, 2). Specimens of pure or putative C. trinacriae from Lazio were not considered for the data-set analysis in order to avoid being misled by the many hybrids found in this area (Solano et al. 2018). All study sites were geo-referenced in decimal degrees WGS84. Date of sampling, region, provinces, locality name, and GPS coordinates are listed in Appendix 1. For comparison, a total of 186 specimens of C. boltonii were studied: 60 males and 19 females from Lazio, 45 males and 17 males from Tuscany, including Elba Island, and 47 males from Lombardy and Piedmont in northern Italy (Fig. 1). Additionally, a number of specimens from central-southern Italy (28♂ and 7♀ C. boltonii and 9♂ and 3♀ C. trinacriae) held in the entomo- logical collections of the following institutes were also compared: Museo Civico di Zoologia di Roma, Italy (MCZR); Istituto di Zoologia Università di Roma “La Sapienza”; Collezioni Dipartimento di Biologia e Biotecnolo- gie Charles Darwin, Roma. As post­mortem changes could influence the ap- pearance of the frontal area and the occipital triangle (Balestrazzi et al. 1982), the museum specimens were only used to test the reliability of these characters during museum studies but are not included in the data-set. Most individuals were caught while patrolling along rivers and torrents with large entomological hand nets. Dragonflies were photographed in the field and immediately released. The study was conducted during specific monitor- ing projects for priority species included in the Habitats Directive commis- sioned to the author, who obtained permission from the administrations of the Aspromonte, Majella, and Nebrodi National Parks and several Nature Reserves. No specimens were collected. The individuals were only handled for photographing and were released immediately. Photographs were always Odonatologica 48(3/4) 2019: 175-201 178 A. Corso taken from standard positions: lateral view, upper- and underside of the ab- domen, head and thorax from above, and head in frontal view. They were taken with a Canon EOS with an 18–50 mm zoom macro lens. The study fo- cused on the morphological variation of the males; in fact, female Cor dule­ gaster are more difficult to find than males, and females C. trinacriaeof and C. boltonii are so similar (Consiglio 1958; Balestrazzi et al. 1982) that reliable identification is not always possible. Therefore, only a small sam- ple of females was analysed and the variability of female characters is only briefly discussed. Regarding the frontal area, a code was assigned to each of the four different patterns encountered: FA − complete absence of dark transversal marking, frons completely yel- low (rarely a tiny darkish spot in the middle); FB − a dark smudge, mostly brownish, across the frons; FC − a well-marked and visible dark transversal bar, though narrow; usu- ally black/blackish; FD − well-defined and bold dark bar, rather long and wide; black (Figs 3−5, 7; Table 2). For the occipital triangle, the following codes were used: OA − completely yellow occipital triangle, only with well-defined and nar- row dark lateral margins; OB − completely yellow occipital triangle with a darkish tinge at the top and often wider dark margins and base; OC − a mostly or partially yellow/yellowish triangle, with a dark line in the middle all the way from the base to the top, usually wide dark lateral margins; OD − fully dark or almost completely dark occipital triangle, sometimes with two tiny lateral yellow spots more or less visible – often only by using a magnifying lens (Figs 3−5, 7; Tables 1, 2). The same codes were used and assigned to the studied C. boltonii. The form of the appendages, which is considered highly species-specific, is only briefly discussed here as it was already the target of recent research (Solano et al. 2018). They were photographed from below and above and Odonatologica 48(3/4) 2019: 175-201 Morphological variability of Cordulegaster trinacriae in Italy 179 Figure 1. Map of Italy showing the study sites. Red dots represent records of Cor­ dulegaster trinacriae and green dots records of Cordulegaster boltonii. Map by courtesy of Michele Viganò. Odonatologica 48(3/4) 2019: 175-201 180 A. Corso their form was examined using a 10× and 20× Leica hand-held lens.