New data on the western Balkan leuciscids Alburnoides and Alburnus (Teleostei, Leuciscidae) from the Vjosa River, Albania

Abstract The first voucher-confirmed record of Alburnus scoranza and the first morphological description of Alburnoides for the Vjosa River system in Albania are reported with a brief discussion of the diagnostic morphological traits and taxonomic assignment of both species.


Introduction
The Vjosa River (Aoos in Greece) belongs to the South Adriatic-Ionian zoogeographical division of Economidis and Bănărescu (1991) and is the southernmost river drainage of the Southeastern Adriatic ecoregion of Zogaris and Economou (2017). It originates in western Greece, flows through Albania, and drains into the southern Adriatic Sea. Some genera of the Greek (e.g., Economidis 1989, Durand et al. 1999, Economou et al. 2007, Geiger et al. 2014, Barbieri et al. 2017, Koutsikos et al. 2019) and the Albanian sections of the Vjosa/Aoos River (e.g., Šanda et al. 2008, Marková et al. 2010, Stierandová et al. 2016 were investigated mostly within wider phylogenetic studies, and summarising lists of fish species in the Albanian section have been also published (Ahnelt and Elvira 1991, Rakaj and Flloko 1995, Shumka et al. 2010, Graf et al. 2017, Meulenbroek et al. 2018, Shumka et al. 2018a,b, Weiss et al. 2018. However, any new data on morphology and distribution of the Vjosa fishes could help for further research, especially in taxonomically difficult groups or species complexes.
Herein, we report the first voucher-confirmed records of Alburnoides based on a historical sample and the Scoranza bleak Alburnus scoranza Bonaparte, 1845 present in the middle and lower part of the Vjosa River drainage in Albania; we also present first morphological data for the Albanian Vjosa populations of these two cyprinids. Their species-level identifications are discussed based on some morphological comparisons.

Materials and methods
The Natural History Museum in Vienna (NMW) houses two small collections of freshwater fishes from the lower and middle course of the Vjosa River, from Selenica and Tepelena, respectively. These fishes were sampled in 1894 at the lower course of the Vjosa River near the town of Selenica (Selenicë) (Ahnelt and Elvira 1991) and in 1914 in the Bença River, a tributary of the Vjosa, near the village of Bença. No ecological data were available for either collection.
For methods and terminology of measurements and counts, and the comparative material, see Bogutskaya et al. (2010).
Identification of the sample as Alburnoides cf. devolli is based on statistical analyses (Fig. 2). See Discussion for the taxonomy of A. devolli Bogutskaya, Zupančič et Naseka, 2012. Colouration (preserved). The body is pale fawn, the back darker than the ventral side. A distinct, black to dark grey stripe extends from the posterior margin of the orbit to the base of the caudal fin. The ventral side of the belly and of the tail is unpigmented. The lateral line is lined dorsally and ventrally by pigment along its entire length, most distinct in its anterior half to about below the origin of the dorsal fin. The fins are hyaline with tiny melanophores lining the dorsal and caudal fin rays, the anterior rays of the anal and the dorsal rays of the pectoral fins. Fig. 3 New record. NMW 87654, 1 specimen, SL 70.8 mm; Albania: Vjosa River system: Selenica (40°32'N, 19°38'E); collected by Pola Expedition, Franz Steindachner, 4 July 1894.
Sexual dimorphism. Though only few specimens were examined, we may report on pronounced sexual dimorphism: the pectoral fin is longer while the pectoral-pelvic distance is shorter in males and the pectoral fin reaches behind the origin of the pelvic fin (Fig. 3a, b). Also, the pectoral fin is markedly rounded with a slightly convex outer margin and the first two branched rays of about similar length forming the apex of the fin in males vs. a clearly pointed fin with a slightly concave outer margin and the first branched ray which is clearly longer than the second one forming the apex of the fin in females. The male NMW 87659:2 has prominent nuptial tuberculation: tubercles densely cover the entire dorsal and lateral head surface down to the lower margin of the interoperculum and the branchiostegal rays, anterior back along the scale margins and on the upper surface of the pectoral fin along all its rays.
Colouration (preserved). The dorsal part of the head and the body is dark grey. The flank and the abdomen are silvery. The fins are hyaline.

Discussion
As the knowledge of the biodiversity in general and of the fish fauna in particular within the Vjosa River system in Albania is very scarce (Rakaj andFlloko 1995, Shumka et al. 2018b), descriptions of fishes from this river system are commonly based on the study of Rakaj (1995). However, the Rakaj's data were mostly based on material from Prespa, Ohrid, and Skadar lakes and their tributaries. This author did not give data for specimens of the Vjosa just indicating the occurrence of a species in this river.
In the publication by Stierandová et al. (2016), the A. ohridanus lineage included the Ohrid Lake sample and some individuals from the Mat, Ishëm and Erzen Rivers -Adriatic drainages south of the Ohrid-Drin-Skadar basin. The range of the A. prespensis species complex embraces Prespa Lake and five Adriatic drainages in the south of Erzen -Shkumbin, Seman, Vjosa/Aoos, Dukati, and Borshi. The internal structure of the A. prespensis complex based on combined data (cytb, ß -actin and S7) (Stierandová et al. 2016: fig. 1) cannot be interpreted from either taxonomic or zoogeographic aspects. As any morphological diagnostic characters of the voucher samples used for the genetic research have not been published, a clear taxonomic assignment of the Aoos (Greek) Alburnoides as well as of the two Albanian species from the Seman River drainage (geographically closest to the Vjosa/Aoos) is still uncertain.
Our morphological data (Table 2, Fig. 2) is not congruent with the molecular data: A. ohridanus is located inside the A. prespensis complex and the whole set of samples that belong to the latter demonstrates a high degree of morphological divergence within the group in general and between some presumptive species, in particular. However, as it can be seen from Table 3 summarising our data for samples out of the A. prespensis complex, they are all different in key diagnostic characters indicating a considerably high morphological diversity of the complex. Our sample is similar to samples from the Aoos in Greece (Barbieri et al. 2017) in having a poorly developed ventral keel which is commonly almost or completely scaled, and 43-49, mean 45.8, lateral-line scales to posterior margin of hypurals (45-50, mean 46.3 in Barbieri et al. (2017). However, the number of branched anal-fin rays is lower, commonly 11½, mean 11.2[ ½] (vs. commonly 12½, mean 11.8[½] in Barbieri et al. (2017).
The entire A. prespensis complex needs a thorough revision, especially with regard to the southern river drainages of Albania (Bogutskaya et al. 2010, Stierandová et al. 2016, Barbieri et al. 2017. The data presented in this study are a first step towards resolving the phylogenetic and taxonomic position of the Vjosa/Aoos A. cf. devolli populations.
The Vjosa population of A. scoranza in Albania was documented as Alburnus alburnus (Linnaeus, 1758) by Ahnelt and Elvira (1994). The Aoos population of A. scoranza in Greece was also first reported as A. alburnus by Economou et al. (2007a) and then as A. cf. scoranza (Economou et al. 2007b). Alburnus scoranza is supposedly distributed in the western Balkans from the Drin drainage, including Skadar and Ohrid lakes, south to the Aoos in Greece where it is restricted to a short section of the middle section of the river within the Konitsa plateau downstream to the Albanian border (Barbieri et al. 2015). Based on COI barcodes, Geiger et al. (2014) showed that A. scoranza (material from Ohrid and Skadar lakes and the Aoos in Greece) is not included in the Adriatic Alburnus clade but is the closest neighbour to a wide group of Alburnus species spread from Portugal and France to Central Anatolia. Mangit and Yeril (2018) included some GenBank-available CO1 sequences of A. arborella (De Filippi, 1844), A. albidus (Costa, 1838, A. belvica Karaman, 1924, and A. scoranza in their analysis of mostly Turkish species and found the same pattern with A. scoranza as a closest sister clade to the three former species plus two from western Turkey. While A. arborella occurs in northern Adriatic basin, the distribution of A. belvica is restricted to Prespa Lake with its tributaries (Kottelat and Freyhof 2007). Alburnus neretvae Buj, Šanda et Perea, 2010 is an endemic species of the Neretva River drainage (Buj et al. 2010) and the distribution area of A. scoranza comprises the basins of lakes Prespa, Ohrid, and Skadar (Kottelat and Freyhof 2007). Economou et al. (2007b) and later Geiger et al. (2014) listed this species for the Greek part of the Vjosa/Aoos River drainage. Shumka et al. (2018a) mentioned A. scoranza in a checklist for the Albanian section of the Vjosa but no exact locality data were given. Therefore, the specimens presented in this study from Selenica are the first voucher-confirmed record of A. scoranza for the Vjosa River system in Albania.
We could only morphologically compare our sample with the limited published data of A. scoranza (Buj et al. 2010; material from the Zeta, Skadar basin; Black Drin, Ohrid basin; and the Mat River, which is the geographically closest drainage south of the Drin). The Vojsa specimens have more numerous anal-fin branched rays, 14½-15½ (vs. 13½-14½); similar number of total lateral-line scales, 45-51 (vs. 46-53); and, the most striking difference, gill rakers 22-25 (vs. 15-20). Interestingly, the Vojsa sample does not differ by the diagnostic counts from two specimens that had been considered syntypes of A. scoranza Heckel & Kner, 1857 from Skadar Lake (NMW 55700: 1 and 2) until it was supposed that the species' name was made available earlier by Bonaparte (1845) (see below). These two specimens have a sharp scaleless keel; total lateral line scales 48, 47; anal-fin branched rays 14½; gill rakers 21, 24; vertebrae 22+19 and 22+20 with predorsal abdominal vertebrae 15 and 16; for measurements see Table 2.
So far, clarification of the taxonomic status of A. scoranza from the Vjosa still needs additional morphological and genetic data, especially from the southern river basins in Albania.
Nomenclatural note on Alburnus scoranza. The most recent publications (e.g., Buj et al. 2010;Barbieri et al. 2015) follow Kottelat and Freyhof (2007: 598) in attributing the authorship to Bonaparte (1845). Bonaparte (1845: 12) lists A. scoranza (species No 122) with a reference to Heckel (no date) and the only morphological trait given in the description is the number of pharyngeal teeth (2.5-5.2). According to Art. 12.1 of the International Code of Zoological Nomenclature (the Code; International Commission on Zoological Nomenclature 1999) this indeed constitutes an available name as it is "accompanied by a description … of the taxon that it denotes". Heckel's publication is most probably dated 1843 where Alburnus scoranza is listed (on page 1036) as a name only (authorship attributed to Heckel) with the locality as Montenegro, among other species names under the description of the genus Alburnus. The pharyngeal teeth 2.5-5.2 are given as a characteristic feature of the genus. This may indicate that Bonaparte only referred to these data from Heckel (1843) and did not examine any A. scoranza specimens himself, so, Heckel's specimens may represent the type series of the species by bibliographic reference according to Art. 72.4.1 of the Code (International Commission on Zoological Nomenclature 1999).
Heckel had apparently examined specimens of A. scoranza as two specimens (as Aspius scoranza Heckel, acquisition number 1843.II.18b) were registered at the NMW from "Cettinje in Montenegro" collected by himself in his 1840 travels. Unfortunately, these specimens have not been found in NMW during recent searches. Cetinje is a city (the historic old capital of Montenegro) located in the Cetinje karst field 12 km from Skadar Lake and even closer to the Rijeka Cernojevića River, an inflow of Skadar Lake. Heckel received two more specimens (acquisition number 1856.VII.26) described by Heckel and Kner in 1857 (page 139 footnote) much later than 1843 from Belotti (sample NMW 55700). In case a designation of neotype to fix the species name A. scoranza is needed in the future, the information presented above on the Heckel's specimens from Cetinje should be taken into consideration to meet the conditions of Art. 75.3 of the Code (International Commission on Zoological Nomenclature 1999).
Recent studies provide evidence that species of Alburnoides and Alburnus Rafinesque were introduced into other river systems (e.g., Simić et al. 2012, Stierandová et al. 2016, Pofuk et al. 2017, Vukić et al. 2019. As intentional and unintentional introductions of non-native fish species are common in Adriatic lake and river systems (e.g., Shumka et al. 2008, Simić et al. 2012, Pofuk et al. 2017, Vukić et al. 2019, historic museum collections provide important information of natural fish distributions (e.g., Palandačić et al. 2017). If several phylogenetic lineages occur in one and the same river drainage, historic museum collections may be of a crucial importance to determine native populations and apply the nomenclaturally correct name.