Taxonomy of Baetis Leach in Israel (Ephemeroptera, Baetidae)

Abstract The taxonomy and systematics of the genus Baetis Leach (Ephemeroptera: Baetidae) in Israel is clarified for the first time as part of an ongoing comprehensive survey of the Israeli mayfly fauna. Six clearly defined species are currently recognized in Israel, four of which are described here as new to science. The validity of all species is supported by a molecular analysis of the mitochondrial COI gene. A key for the identification of the Israeli species based on the nymphal stage is provided, as well as data on their distribution patterns and ecology. The local fauna represents four Palearctic species groups, three of which reach their limit of distribution range in Israel. Baetis species typically inhabit lotic, pristine habitats in northern Israel, with few exceptions for some species that can be found in the Dead Sea area or in ephemeral ponds.


Introduction
Baetis Leach, 1815 is one of the richest mayfly genera with approximately 160 species worldwide (Barber-James et al. 2008) and more than 80 species in the Palearctic Region (Barber-James et al. 2013).The taxonomy of the genus is subject to ongoing study (Gattolliat and Nieto 2009) and many undescribed and cryptic species are con-tinuously being discovered (e.g., Williams et al. 2006, Leys et al. 2016).For practical reasons, the European species of the genus were divided into eleven species groups by Müller-Liebenau (1969) based on their morphological characters, and this classification is still widely used today.Some of these species groups are considered today as valid genera or subgenera (e.g., Waltz et al. 1994;Thomas and Dia 2000;Jacob 2003).
Some Baetis species are widely distributed whereas others are confined to very limited areas.All feed mainly on detritus and periphyton (Bauernfeind and Soldán 2012).In the Levant, nymphs usually occupy habitats of pristine running water, are considered to be sensitive to environmental conditions at least to some extent, and are therefore restricted to more protected habitats.Nevertheless, some species are more tolerant and can be found in more disturbed sites.These characteristics make Baetis species ideal candidates for use as bioindicators for water quality (Bauernfeind andMoog 2000, García et al. 2014).However, generating a mayfly-based index necessitates recognition of relevant species and their ecological requirements (Resh and Unzicker 1975), and such knowledge is lacking for the taxonomically difficult Baetidae in many regions.In Israel, the taxonomic knowledge on aquatic insects as a whole is limited (e.g., Botosaneanu and Gasith 1971, Bromley 1988, Wewalka 1989, Dumont 1991), although it is essential for the implementation of bioassessment tools for the local stream systems.
The knowledge about mayflies from the Levant varies with country.The Lebanese and Syrian faunas are relatively well known, mostly thanks to studies by Dia, Thomas and Koch (e.g., Koch 1981, 1988, Thomas and Dia 1983, 1984, 1985, Thomas et al. 1988).By contrast, less than ten species are currently known from Jordan (Gattolliat et al. 2012) and Egypt (Hassan and Abdel Fattah 2007), reflecting the more arid nature of these countries as well as insufficient research.
The Israeli mayfly fauna currently numbers 17 species in seven families (Baetidae, Caenidae, Ephemerellidae, Heptageniidae, Leptophlebiidae, Oligoneuriidae and Prosopistomatidae).Except for Baetidae, the fauna is considered to be well-known, and only limited new discoveries are expected.Samocha (1972) was the first to conduct a thorough investigation on the local mayflies in his MSc thesis, which has never been published.Demoulin (1973) studied the material collected by Samocha and published the first paper on Israeli mayflies, focusing on the Heptageniidae, and Malzacher (1992) and Sartori (1992) provided additional information on most of the remaining families.By contrast, mayflies have almost never been studied in the Palestinian Authority; Samocha (1972) sampled a handful of sites that yielded few records, followed by sporadic field surveys by Israeli ecologists, all suggesting that the fauna in this region is similar, yet poorer, than that of semi-arid regions in Israel.
The Baetidae, by far the richest and most common family in Israel, remain poorly studied.Samocha (1972) reported 20 morphospecies from the country (although the true number must be lower because he did not associate nymphs and adults), and included only one named species, "Cloeon dipterum" (Linnaeus, 1761).Baetis samochai Koch, 1981 andB. monnerati Gattolliat &Sartori, 2012 were subsequently described from Lebanon, Syria, or Jordan and are reported here from Israel for the first time.
In the present paper, we provide the first comprehensive taxonomic treatment of the genus Baetis in Israel, based on integrative study of nymphal morphology and molecular analysis.We include a key to nymphs of all species and a description of four new species.The present study contributes to a better understanding of the Israeli mayfly fauna and may promote the development of local biological indices for water quality.

Materials and methods
Collecting was done in over 400 sites around Israel and the Palestinian Authority (Figure 1; Supplementary File 1) between 2014-2018 throughout the year, and covered diverse types of aquatic habitats (Figure 2).Baetis nymphs were collected using a hand net or picked manually from rocks and pebbles and preserved in ethanol.Collected specimens were studied under a Leica M125 or M205 stereomicroscope.Microscope slides were prepared from body parts important for diagnosis, fixed in Canada Balsam, and drawn from a drawing tube mounted on a Leica DM1000 or Olympus BX51 compound microscopes.Morphological descriptions followed Hubbard (1995).Body surface of Baetis nymphs is usually covered by scales and setae on enlarged bases.These tend to be lost often during the mounting process, and therefore do not appear in most microscope slides and resulting figures (Kluge et al. 2018).Measurements in the following descriptions are based on 20-36 individuals for each species.The material examined included nymphs only.A small number of adults was collected in the field or reared in the lab, but not enough information is available to associate them with the nymphal stages, therefore they will be dealt with in a future study.Most of the material used in this study, whether preserved in ethanol or on microscope slides, is deposited in the Steinhardt Museum of Natural History at Tel Aviv University, Israel (SMNH-TAU), including all holotypes and most paratypes.Remaining paratypes are deposited in the Musée Cantonal de Zoologie at Lausanne, Switzerland.Museum personal identifiers are mentioned for holotypes.
For the phylogenetic reconstruction we used freshly collected nymphs from populations throughout the distribution range of each species in Israel.DNA was extracted using the DNAeasy blood and tissue kit and BioSprint 96 extraction robot (Qiagen Inc., Hilden, Germany), implementing the non-destructive protocol outlined by Vuataz et al. (2011), which enabled post-extraction morphological study of specimens.The 'barcoding section' of the mitochondrial cytochrome c oxidase subunit I (COI) was PCR-amplified with the primers HCO2198 and LCO1490 (Folmer et al. 1994).Polymerase Chain Reaction was conducted in a volume of 25-30µl, consisting of 2-6µl DNA template, 1µl of 10 pmol/µl of each primer, 2.5 µl 10 mM dNTP solution, 3-3.5 20 mM MgSO4, 2.5µl Taq buffer, and 1 unit Taq polymerase.Optimized PCR conditions included initial denaturation at 94°C for 5min, 35-40 cycles of denaturation at 94°C for 30-40 s, annealing at 47-54°C for 30-45 s, and extension at 72°C for 40-60 s, with final extension at 72°C for 7-10min.Automated sequencing was carried out in Hy Laboratories (Rehovot, Israel) or in Microsynth (Balgach, Switzerland).
Molecular reconstruction was conducted on 48 newly obtained sequences, as well as three B. monnerati specimens from Jordan (Gattolliat et al. 2012), and four reference sequences obtained from GenBank (http://www.ncbi.nlm.nih.gov/Genbank) and from Rutschmann et al. (in prep.), to represent the four species groups dealt with in this study.All GenBank accession numbers and collecting details of the specimens are given in Supplementary File 2. Sequence chromatograms were inspected and edited using Geneious v.7.1.5(Biomatters Ltd.).Alignment, reconstruction, and genetic distance calculations were conducted in MEGA v.7.0 (Kumar et al. 2015).We selected GTR+G+I with partial deletion as the most appropriate model for reconstruction (based on lowest AICc and BIC scores), and conducted a Maximum Likelihood analysis with 1000 bootstrap replicates.

Results and discussion
In the present study, two described and four new species of Baetis were found in Israel, all are well supported by the molecular phylogenetic analysis of mitochondrial COI sequences (Figure 3).Inter-and intraspecific genetic differences were found to be ≥11.9% and ≤3.5%, respectively (Table 1).The phylogenetic analysis also identified three independent and highly supported clusters, representing groups of individuals which could not be distinguished morphologically and did not differ in their distribution patterns from the six recognized species (cryptic species I with Baetis golanensis, cryptic species II with B. monnerati, and cryptic species III with B. noa).We consider them to be cryptic species but refrain from describing them until further morphological, molecular, and ecological studies.

Genus Baetis Leach, 1815
Diagnosis.The main diagnostic morphological characteristics of the genus pertain to nymphs and include the cylindrical body, two pairs of wing pads, absence of setae between prostheca and mola of both mandibles, simple stout prostheca on both mandibles, presence of femoral villopore, robust tarsal claws with a single row of denticles, gills consisting of a single lamella on abdominal segments I-VII, unmodified paraproct and three caudal filaments (Bauernfeind and Soldán 2012).The present study is focused only on Baetis s.s. and the following descriptions include only nymphs.Differential diagnosis.Baetis aureus is unique within its potential species groups in having a relatively short median caudal filament (half-length of cerci) and scale bases on the surface of the abdominal terga only slightly wider than seta bases.In Israel it is distinguishable by the long gills, elongate body, and wide, triangular spines along the distal margin of terga.Description.Length (mature nymphs).Female (n = 17): 4.2-4.5 mm (summer generation) to 5.3-7.2mm (winter generation); cerci 2.6-5.4 mm; median caudal filament 1.7-2.7 mm.Male (n = 8): 4.5-4.7 mm (summer) to 6.0-7.1 mm (winter); cerci 2.9-4.1 mm; median caudal filament 1.6-2.6 mm.
Colouration.General colour light brown to yellow (Figure 4A).Head light brown, antennae, clypeus and labrum ecru.Turbinate eyes in male nymph amber-orange.Thorax brown with a few pale marks but without clear pattern.All legs whitish, brownish hue sometimes on middle of trochanter and femur, brown shade on claw and distal 1/3 of tarsus.Abdominal terga yellowish brown, with pale narrow posteriomedial triangular spot forming dashed dorsal line along abdomen.Abdominal sterna ecru to pale yellow.Gills milky, semi-transparent, costal margins darker, tracheation brownish purple.Cerci and median caudal filament uniformly ecru without bands or pattern.
Head.No carina between antennae; pedicel almost bare (Figure 5A).Labrum (Figure 5B): dorsal surface with scattered, fine, short setae and seta bases, with one median pair of long setae; lateral margins each with distal arc of 5-6 long, simple, stout setae and 4-5 lateral setae; ventral surface with 5-6 small, stout setae laterodistally; distal margin with row of 30-40 fine, long, feathered setae.Hypopharynx (Figure 5D): lingua tri-lobed; surface covered with minute hair-like setae, denser and stouter apically; lingua and superlingua covered with minute, stout setae; base of superlingua laterally serrated.Right mandible (Figure 5C) with incisors composed of two sets of four and three denticles, outer denticles more prominent than others; prostheca with 6-7 denticles; mola apex with tuft of setae.Left mandible (Figure 5E) with incisors composed of six denticles, outer one broadest and most prominent; prostheca with six denticles and few long, soft setae; space between prostheca and mola slightly crenulate; mola apex without tuft of setae; base of mola with few spines.Maxillae (Figure 5F) with four broad teeth; lacinia with one row of small setae and long, serrated setae; row of 4-6 setae at base of lacinia; one seta perpendicular to lacinia margin; palpus 2-segmented, segments of similar length; segment II with small nipple, covered with sparse minute setae, apical scale absent.Labium (Figure 5G): glossa slightly shorter than paraglossa; glossa inner margin and apex with long, simple setae; paraglossa not curved; apex with apical stout, blunt seta and distal quarter with three rows of long setae; labial palpus 3-segmented; segment I as long as segments II and III combined; segment II with noticeable distolateral protuberance ("thumb") and dorsal row of 5-7 long, pointed setae.
Abdomen.Terga shagreened with few thin setae, seta bases and very small scale bases (only slightly wider than seta bases); distal margin of all terga with row of triangular spines as broad as long (spines longer and more pointed on terga VII to IX), with spaces between them no broader than spine length (Figure 6C).Gill I oval, reduced, without marginal spines and visible tracheation (Figure 6D); gills II to VII elongate, 1.7 times longer than following tergum; margins thicker with very fine serration in proximal half; branched tracheae clearly visible (Figure 6E).Paraproct (Figure 6F) with elongate scales, hair-like setae and seta bases; margin with 20-30 regular triangular spines; postero-lateral extension with few scales, margin with 14-20 triangular spines of similar size.
Affinities.Baetis aureus exhibits the main characters of the B. vernus and B. buceratus species groups sensu Müller-Liebenau (1969) and cannot be assigned to any of them with certainty.Therefore, it is compared here to species of both species groups.Characters typical to both groups include mandibles with bigger outer tooth, labrum with submarginal arc of less than eight setae, tarsal claws without subapical setae, distal margin of abdominal terga with triangular spines, relatively long gills, and generally inconspicuous pattern of the terga (Bauernfeind and Soldán 2012).Baetis aureus differs from all known species of these two species groups by the median caudal filament that is slightly longer than half the length of its cerci (whereas in other species the median caudal filament is almost as long as the cerci, except in B. zdenkae Soldán & Godunko, 2009), and by the small size of the scale bases on the surface of the abdominal terga.
In the B. vernus species group, seven species were reported from the West Palearctic region, and differ from B. aureus as follows: Baetis vernus Curtis, 1834 has a mola with two small auxiliary spines at the outer side of the subtriangular process (figure 91 in Eiseler 2005).In B. liebenauae Keffermüller, 1974 the outer sets of incisors in the mandibles are fused, and the spines on the distal margin of terga are blunt and rounded (Keffermüller 1974).In B. macrospinosus Koch, 1985 the setae on the dorsal margin of femora are longer and apically rounded, terga are covered with abundant scale bases, spines on distal margin of terga are blunt and rounded, and dorsal pattern of abdomen is well-marked (Koch 1985).In B. macani Kimmins, 1957 the distolateral protuberance on segment II of the labial palpus ("thumb") is considerably developed (Müller-Liebenau 1969).The gill tracheation of B. tracheatus Keffemüller & Machel, 1967 is conspicuous.The submarginal arc of setae on the labrum of B. tracheatus and B. subalpinus Bengtsson, 1917 is reduced to 2-3 setae (Müller-Liebenau 1969).Finally, B. samochai Koch, 1981 is characterized by long and sharp spines along the distal margin of terga, its maxillary palpus is longer than the galealacinia, and the dorsal pattern on its abdomen is different (Koch 1981).
Baetis aureus differs from all other known species of the B. buceratus species group (see Soldán and Godunko 2009) as follows: in B. buceratus Eaton, 1870, the submarginal distal arc on the labrum consists of only 3 setae, and spines on the distal margin of terga are narrow and blunt (Müller-Liebenau 1969).In B. spei Thomas & Dia, 1985, a geographically close relative from Lebanon, the shape of the labial palpus is different, teeth on the outer set of the left mandible incisor are wider, spines on the distal margin of terga are rounded and blunt, marginal spines on paraproct are irregular and of variable shapes (Thomas and Dia 1985).In B. pentaphlebodes Ujhelyi, 1966 segment III of the labial palpus is shorter (compared to segment II).In B. zdenkae from Rhodes, Greece, the incisors of the right mandible are not arranged in a decreasing size order, more setae are present on the paraglossa base, and less marginal spines are found on the paraproct (Soldán and Godunko 2009).Finally, in B. monnerati the setae on the dorsal margin of femora are long, and the gills are oval (Gattolliat et al. 2012).
Etymology.Aureus (Latin for golden) refers to the general colour of the nymph body.Distribution and ecology.This species is common in the northern regions of Israel: Lower and Upper Galilee, Hula Valley and Golan Heights, and rare in the Yarqon stream.It is found in habitats of running, pristine water, particularly in small creeks but also in larger streams such as the Keziv and Zippori (Figure 2C, E, F).The substrate is usually composed of stones of different sizes, and localities with dense submerged vegetation are preferred.Mature nymphs were collected mostly in spring (March-May) and fall (October-November).

Differential diagnosis.
Among the species with well-developed median caudal filaments in the B. lutheri species group, B. golanensis is the only one with a combination of the following characters: right mandibular incisors of similar size, irregular blunt quadrangular spines on the distal margin of terga, and non-sclerotized protuberances next to the coxae.This is the only species in Israel with a developed median caudal filament that also has ventral protuberances near coxa bases and subapical setae on the claws.
Colouration.General colour brown (Figure 4B).Head brown, antennae ecru, area around compound eyes and ocelli ecru.Turbinate eyes in male nymph amber.Thorax dark brown.Legs ivory to ecru, claws, apex of femora and tibiae brown.Abdominal terga uniformly brown, terga V, IX and X sometimes distally lighter.Abdominal sterna ivory to beige.Gills almost transparent, tracheation light brown.Cerci ecru to brown, without bands or pattern, median caudal filament sometimes lighter.
Head.No carina between antennae; antennae with few fine setae, pedicel without distal lobe (Figure 7A).Labrum (Figure 7B): dorsal surface with scattered, fine, short setae and seta bases, with one median pair of long setae (sometimes with one additional pair of shorter setae); lateral margin with distal arc of 3-4 long, simple, stout setae and 3-8 lateral setae; ventral surface with five small, stout setae laterodistally; distal margin with row of 30-40 fine, long, feathered setae.Hypopharynx (Figure 7D): lingua tri-lobed; surface of lingua and superlingua densely covered with thin setae; lateral margin of superlingua serrated proximally.Right mandible (Figure 7C) with incisors composed of two sets of four and three denticles, all denticles nearly of same size; prostheca with small pointed denticles; space between prostheca and mola without setae or crenulation, mola apex with tuft of setae; base of mandible with many short, thin setae and seta bases.Left mandible (Figure 7E) with incisors composed of six denticles; prostheca with four broad denticles and comb-shaped structure; space between prostheca and mola without setae or crenulation; base of mola without spines; base of mandible with many setae and seta bases.Maxillae (Figure 7F) with four broad teeth; lacinia with one row of small setae and long, serrated setae; base of lacinia with row of five long, stout setae; one seta perpendicular to lacinia margin; palpus 2-segmented, segments I and II subequal; segment II with few minute, thin setae apically, apical nipple with single scale.Labium (Figure 7G): glossa thin, slightly shorter than paraglossa; glossa inner margin and apex with long, stout setae; paraglossa thick, not curved, with 4-5 setae mediodorsally; paraglossa with apical stout, blunt seta and distal third with three rows of long, feathered setae; palpus 3-segmented; segment I same length as segments II and III combined; segment II with distolateral protuberance slightly developed and dorsal row of 4-6 long, pointed setae; segment III symmetrical, conical, with distinct nipple apically, covered with thick setae.Mentum and palpi covered with many short fine setae ventrally.
Abdomen.Terga shagreened, with few thin setae and many seta bases, without scales or scale bases; distal margin of all terga with irregular row of blunt, quadrangular spines, with occasional fine seta (Figure 8C), spines absent or rare on terga I and II, more abundant and developed on following terga.Gill I slightly reduced, without visible tracheation (Figure 8D); gills II to VII oval, without marginal spines, main tracheation branched and pigmented (Figure 8E).Paraproct (Figure 8F) surface with few hair-like setae and seta bases; margin with 13-15 short, regular, triangular spines; postero-lateral extension with few seta bases, margin with 18-21 small, triangular spines, sometimes with few submarginal, spatulated scales.
Affinities.The new species clearly belongs to the Baetis lutheri species group sensu Müller-Liebenau (1969) based on the reduction of the median caudal filament, blunt spines on distal margin of terga, two subapical setae on the claws, and single scale on the apical nipple of the maxillary palp (Bauernfeind and Soldán 2012).
Baetis lutheri Müller-Liebenau, 1967 appears to be the closest species to B. golanensis, based on its morphology, yet differs from it by the incisors of the right mandible, which is variable in size, the arrangement and shape of the setae along the dorsal margin of femur, and the more regular, blunt teeth along the distal margin of the terga (Müller-Liebenau 1967, 1969).In Baetis vardarensis Ikonomov, 1962 4E).Moreover, B. mirkae from Cyprus has many spatulas on body surface, and an additional row of long setae on the proximal part of the dorsal margin of femora, which distinguish it from B. golanensis.It also differs from B. golanensis and B. lutheri by lacking the brush scales on femora (Soldán and Godunko 2008).Baetis meridionalis Ikonomov, 1954, which was assigned to the Baetis lutheri species group by Müller-Liebenau (1969), differs from B. golanensis by the lack of scale at the apex of its maxillary palpus, short setae on margin of femora and shape of spines on the distal margin of terga.It is noteworthy that the description of B. meridionalis is superficial, it has no type material that could be examined, and its assignment to this species group is uncertain (Soldán and Godunko 2008;Bauernfeind and Soldán 2012).
Baetis lutheri has a wide distribution in the West Palearctic (Bauernfeind and Soldán 2012) but recent molecular analysis has shown that it may constitute a complex of closely related species (Tenchini et al. 2018).Koch (1988) reported it from Lebanon and Syria, but these reports may refer to B. golanensis.Baetis golanensis also corresponds to the undescribed "Baetis A12" mentioned by Samocha, also from Israel (1972: 44, pls XVIII-XIX).
Etymology.The species name reflects its presently known distribution range, the Golan Heights.
Distribution and ecology.Baetis golanensis is a rare species in Israel.It was reported by Samocha (as "Baetis A12") from springs and streams in the western Golan and a few localities along the upper Jordan River.This restricted distribution is confirmed in the present study.Two distinct habitats are typical for B. golanensis in Israel: streams with large water discharge and rapid currents (upper Jordan River; Figure 2D), and small tributaries with shallow, quiet water running over basaltic pebble substrate (small streams and spring-fed brooks in the Golan Heights; Figure 2E).In all cases, the water is pristine, well oxygenized (>85% dissolved oxygen) and contains aquatic vegetation.In all collecting events of the species, temperatures ranged between 19-25°C and salinity levels between 160-170 ppm.In Israel, mature nymphs were collected mainly in spring and early summer (May-July).Gattolliat et al. (2012).This is the only Israeli species that exhibits a combination of developed, blunt dorsal setae on the femora, a regular row of short spines on the distal margin of the abdominal terga, and body and gills that are not elongate.The colour pattern on the abdomen is usually clearly visible (Figure 4C), but a similar pattern may occasionally be seen in other species.Baetis monnerati populations in various parts of Israel, Jordan and the Palestinian Authority exhibit a wide morphological diversity compared that in congeners, e.g. in size, colour pattern and size of spines on tergite distal margins.
Affinities.Baetis monnerati belongs to the B. buceratus species group sensu Müller-Liebenau (1969) and exhibits 21 of the 22 characters of the group as defined by Soldán and Godunko (2009).It was discussed in detail and compared to related species by Gattolliat et al. (2012).
Distribution and ecology.Baetis monnerati is the most abundant and widespread Baetis species in the Israeli fauna.It is common in the Golan Heights, Hula Valley, Upper and Lower Galilee, Jordan Valley, eastern Judean Mountains, and the Dead Sea area.Outside of Israel it is found in Jordan (Gattolliat et al. 2012;Alhejoj et al. 2014;Ramadan and Katbeh-Bader 2018) and Iran (Bojková et al. 2018).Suitable habitats for B. monnerati in Israel vary greatly and include brooks and streams of various sizes

Differential diagnosis.
Baetis noa is distinguishable from all known species of Rhodobaetis by the following combination of characters: seven setae on labrum, three rows of setae on paraglossae, triangular spines along tergal margins (tergum III and onward), spines on gill margins, ca. 15 triangular teeth along paraproct margin, and 6-8 triangular spines of similar size along cercotractor margin.This is the only representative of Rhodobaetis in Israel, and therefore the only one to exhibit the group characteristics, namely body covered by spatulated scales (particularly along the distal margin of the abdominal terga) and stout spines along the gill margins.
Colouration.General colour brown (Figure 4D).Head brown with ecru spots on frons, around compound eyes and around antennal bases, labrum light brown.Antennae ecru.Turbinate eyes in male nymph amber-brown.Thorax brown with a few pale marks but with no clear pattern.Legs whitish, with light brown spot on dorsal femora, usually with proximal and distal brownish marks on femora and tibiae.Abdominal terga I-IV and VI-VIII brown with fade, pale triangular posteromedial and posterolateral spots.On terga V-IX pale spot larger, covering almost entire posterior half of tergum, with brown margins.Tergum X brown.On all terga a pair of median dark dots occasionally present.Abdominal sterna ecru to light brown.Gills milky, margins dark brown and tracheation violet.Cerci and median caudal filament ecru without bands or pattern.
Head.No carina between antennae; pedicel with elongate spatulated scales apically (Figure 12A).Dorsal surface of labrum (Figure 12B) with scattered fine, hair-like setae and seta bases, one median long seta and distolateral arc of setae composed of six long, simple setae; lateral margin with ca.ten small, fine setae; ventral surface with 2-5 small, stout setae laterodistally; distal margin with row of 30-40 fine, long, feathered setae.Hypopharynx (Figure 12D): lingua and superlingua apically covered with minute, stout setae; base of superlingua laterally serrated.Right mandible (Figure 12C) with incisors composed of seven denticles; prostheca with small denticles; space between prostheca and mola without setae or crenulation; mola apex with tuft of setae.Left mandible (Figure 12E) with incisors composed of six denticles; prostheca with four broad denticles and comb-shaped structure; space between prostheca and mola crenulate, without setae; mola apex with tuft of setae.Maxillae (Figure 12F) with four broad teeth; lacinia with row of abundant small setae ending with stouter, longer setae, second row with two serrated, stout dentisetae; base of lacinia with row of 5-6 long, stout setae; one seta perpendicular to lacinia margin; palpus 2-segmented; segment II almost as long as segment I; segment II with sparse thin setae, apical nipple carrying single short, stout scale.Labium (Figure 12G): glossa shorter than paraglossa; glossa inner margin and apex with long, fine setae; paraglossa slightly curved; apex with stout, blunt seta and distal quarter with three rows of long, simple setae; labial palpus 3-segmented; segment I as long as segments II and III combined; segment II with slightly developed distolateral protuberance, and dorsal row of five long, pointed setae; segment III apex with small, thin setae.
Thorax.Forelegs (Figure 13A): trochanters almost bare, with few short setae.Femora with dorsal row of ca. 30 mid-sized, apically rounded setae, sparser distally; one submarginal row of fewer, much shorter setae; dorsoapical setal patch composed of ca.seven stout setae and no thin setae; ventral margin with pointed, stout, short setae, distributed mostly on proximal half; surface almost bare.Tibiae with dorsal row of stout setae and few apical thin setae; ventral margin with evenly distributed row of small, pointed setae; tibiopatellar suture present.Tarsi with ca.ten pointed setae ventrally; dorsal row of ca.20 minute setae; one pointed seta at ventral tarsus-claw meeting point.Tarsal claws (Figure 13B) hooked with one row of 9-13 acute teeth.Mid-and hindlegs similar to forelegs.
Abdomen.Terga densely covered with numerous spatulated scales, scale bases and few thin hair-like setae; distal margin of all terga with numerous spatulas, terga I to IV without spines, terga V and VI with few broad, blunt triangular spines (Figure 13C), abundant on terga VII to IX. Gill I narrow and reduced, both margins serrated (Figure 13D); gills II to VII elliptic, costal margin with robust spines, tracheation branched and clearly visible (Figure 13E).Paraproct (Figure 13F) with abundant scale bases and almost no setae, margin with 13-16 broad, triangular spines and submarginal row of spatulas; postero-lateral extension with numerous scale bases, margin with 6-14 triangular spines of similar size, submarginal row of spatulas and lateral row of small setae.Affinities.Baetis noa belongs to the subgenus Rhodobaetis Jacob, 2003 (Baetis rhodani species group sensu Müller-Liebenau 1969) and exhibits the group characteristics, such as the presence of spatulas on the surface of terga, pedicel, paraproct and femora, and gills which generally bear spines along margin (Jacob 2003, Godunko et al. 2004).The morphological attributes of the 22 Palaearctic species in the group have been reviewed by Godunko et al. (2004Godunko et al. ( , 2015)), Soldán et al. (2005) and Gattolliat and Sartori (2008).
The Central European species B. rhodani rhodani (Pictet, 1843) (B.rhodani s.s.) differs from B. noa by having long setae on the dorsal margin of femora and not many tergal scales (Gattolliat and Sartori 2008).Baetis noa also differs in the shape of the labial palpus, number of teeth on the claws and spatula density on most of its body surface.The closest relative to B. noa geographically is B. bisri Thomas & Dia, 1983, which was originally described from Lebanon.Despite the geographical proximity, some important characters distinguish the two species: B. bisri has no spines on the gill margins, 5-6 rows of setae on the paraglossae, a different tergal pattern, and a paraproct with less marginal triangular spines and scales of a different shape (Thomas and Dia 1983).Baetis noa also has a wider labrum compared to these species.Other than B. bisri and B. rhodani, two more Rhodobaetis species were reported from Turkey: B. braaschi Zimmermann, 1980, and B. vadimi Godunko, Palatov & Martynov, 2015(Kazancı and Türkmen 2016;Salur et al. 2016).Baetis gemellus Eaton, 1885 and B. pseudogemellus Soldán, 1977 are excluded, as explained by Godunko et al. (2015).Unlike B. noa, no spines are present on the gill margins of B. braaschi (Bauernfeind and Soldán 2012) and B. vadimi (Godunko et al. 2015).Baetis milani Godunko, Prokopov & Soldán, 2004 from the Crimean Peninsula has no triangular spines on the posterior margin of terga and very abundant minute denticles on its cercotractor (Godunko et al. 2004).The North African B. sinespinosus differs from B. noa by having more submarginal setae on the labrum, four setal rows on the paraglossa, fewer tergal scales, and considerably less marginal teeth on the paraproct (Soldán et al. 2005).Rhodobaetis was also reported from Cyprus by Soldán and Godunko (2008), who described a new species, B. irenkae Soldán & Godunko, 2008, presumably endemic to the island.Baetis irenkae differs from B. noa by the shape of its labial palpus, shape and abundance of spatulas on the distal margin of terga, and number and shape of spines on the margin of cercotractor.The most similar species to B. noa morphologically is B. tauricus Godunko & Prokopov, 2003 which is found exclusively in the Crimean Peninsula.However, the two species differ by the number and size of the spines along the margin of the cercotractor.
Baetis noa matches the characters of the undescribed "Baetis L53" as outlined in Samocha (1972;p. 47 and plate XX therein).In his review of the Israeli mayfly fauna, this was the only species that had spines on its gill margins and a nipple on the apex of its maxillary palpus.It also matches in colour and distribution.
Etymology.The name is a noun in apposition.The species is dedicated to Noa Truskanov, the partner, source of inspiration, and closest friend of the senior author.
Distribution and ecology.This species is known from the tributaries of the Jordan River and from brooks and springs in the Golan Heights, where it inhabits streams of diverse sizes and current velocities (Figs 2A, E).Typical substrate in its habitats is composed mainly of pebbles and rocks of various sizes, as well as rich epilithic and submerged vegetation.Mature nymphs were collected mostly in spring (March-May), but also in fall (October-November). Material

Differential diagnosis.
Within the Baetis lutheri species group, B. pacis is distinguishable by the following combination of characters: greatly reduced median caudal filament, non-sclerotized protuberances next to coxae, and body not covered with spatulae.In Israel it is easily recognized by its very short median caudal filament.
Colouration.General colour brown (Figure 4E).Head brown with light vermiform mark, antennae ecru.Turbinate eyes in male nymph amber.Thorax brown.Legs ivory to whitish, claws, apex of femora and tibiae dark brown, dorsal face of femora with medium brown central mark.Abdominal terga light brown with two central dark brown spots more or less expanded, generally also darker laterally and distally, terga V, VI, IX and X brighter.Abdominal sterna ecru to pale brown.Gills milky, semi-transparent, almost no visible tracheation.Cerci ecru to light brown, without bands or pattern.
Head.No carina between antennae; pedicel almost bare, without distal lobe (Figure 14A).Labrum (Figure 14B): dorsal surface with scattered fine, short setae and seta bases, with one median pair of long setae; lateral margin with distal arc of five long, simple, stout setae and 6-8 lateral setae; ventral surface with 5-6 small, stout setae laterodistally; distal margin with a row of 30-50 fine, long, feathered setae.Hypopharynx (Figure 14D): lingua tri-lobed; surface of lingua and superlingua densely covered with medium thin setae; lateral margin of superlingua serrated proximally.Right mandible (Figure 14C) with incisors composed of two sets of four and three denticles, outer denticles of each set more prominent; prostheca with small, pointed denticles; space between prostheca and mola without setae or crenulation; mola apex with tuft of setae; base of mandible with many short, thin setae and seta bases.Left mandible (Figure 14E) with incisors composed of 6 denticles, inner denticle with additional minute teeth; prostheca with 4-5 broad denticles and comb-shaped structure; space between prostheca and mola without setae or crenulation; base of mola with no spines; base of mandible with many setae and seta bases.Maxillae (Figure 14F) with four broad teeth; lacinia with one row of small setae and long, serrated setae; base of lacinia with row of four long, stout setae; one seta perpendicular to lacinia margin; palpus 2-segmented, segments I and II subequal; segment II with few minute, thin setae apically, and apical nipple with single scale.Labium (Figure 14G): glossa shorter than paraglossa; inner margin and apex of glossa with medium, stout setae; paraglossa not curved, dorsal side with inner 4-6 setae; apical stout, blunt seta; paraglossa apex and distal third with four rows of long, simple setae; labial palpus 3-segmented; segment I similar in length to segments II and III combined; segment II with distolateral protuberance slightly developed, and dorsal row of 4-5 long pointed setae; conic segment III symmetrical, with apical distinct nipple, covered with needle-shaped blunt setae.
Thorax.Forelegs (Figure 15A): coxae almost bare.Trochanters with few ventral minute, stout setae.Femora with one or two dorsal rows with total of ca.40 stout setae, no longer than 1/4 of femur width, denser proximally; ventral row of ca.20 minute, stout setae; dorsoapical setal patch made of maximum five minute setae and few thin setae; surface almost bare.Tibiae with dorsal row of thin, short setae and few scales; ventral margin with minute, stout setae and apical brush of thin setae; tibiopatellar suture present.Tarsi with 6-13 ventral pointed setae; dorsal margin with row of short, thin setae; one pointed seta, shorter than most ventral setae, at ventral tarsus-claw meeting point.Tarsal claws (Figure 15B) hooked, with one row of 7-11 acute teeth and two subapical thin setae.Dorsal margin of femora, tibiae and tarsi with scattered feathery scales.Mid-and hindlegs similar to forelegs.Round, unsclerotized protuberances, sometimes hardly seen, adjacent to coxa bases (Figure 9).
Abdomen.Terga shagreened with few thin setae and many seta bases, without scales; distal margin with row of blunt quadrangular spines (Figure 15C).Gills I to VII oval, without marginal spines, main tracheation not pigmented and poorly branched (on gills II to VI main trachea sometimes slightly visible; Figures 15D, E); gills I and VII slightly reduced.Paraproct (Figure 15F) surface with few hair-like setae and seta bases; margin with 10-15 short triangular spines and short thin setae; postero-lateral extension with seta bases, margin with 15-20 small triangular spines.Median caudal filament extremely short, approximately ten segments long.
Affinities.The species belongs to the Baetis lutheri species group sensu Müller-Liebenau (1969) based on its morphological characteristics (see details under B. golanensis above).
Baetis lutheri differs from B. pacis by having longer setae on the dorsal margin of femora, densely shagreened terga surface and less reduced median caudal filament (Müller-Liebenau 1969).Baetis mirkae from Cyprus differs from B. pacis by having wider labrum with fewer dorsal long setae, only three rows of setae on the paraglossae, broader labial palpus, more setae on the femora and tibiae, terga not shagreened, rounded teeth on distal margin of terga, and generally more spatulas and setae on the body surface than in B. pacis (Soldán and Godunko 2008).The European species B. vardarensis is characterized by having unique sclerotized, pointed protuberances next to the coxae (Müller-Liebenau 1974: fig. 4i;Eiseler 2005: figs 76-77), which, in the case of B. pacis, are rounded and not sclerotized, exhibiting the more common situation in the group.Moreover, B. vardarensis has a hypopharynx with a uni-lobed lingua, and dorsal line of long setae on the femur margin (Ikonomov 1962).Within the lutheri species group, B. pacis, B. estrelensis, B. mirkae and B. nigrescens can be distinguished by their greatly reduced median caudal filament, only a few segments long, while other species have a medial caudal filament which is at least as long as 1/4 (B.vardarensis) or 1/2 (B.golanensis, B. lutheri, B. meridionalis) of the cerci.The number of rows of long setae on the proximal part of the dorsal margin of femora varies among species: one row in B. lutheri and B. golanensis, 2-3 rows in B. mirkae, and 4-5 rows in B. vardarensis (Müller-Liebenau 1974: fig. 5a, b;Soldán and Godunko 2008).
Baetis pacis generally has one or two rows of setae, with occasional additional setae that may appear as a third row.Variations can be observed between specimens and even between legs of the same individual.Baetis pacis clearly differs from B. estrelensis and B. nigrescens by the shape of the labial palp (much slenderer in B. estrelensis and B. nigrescens), and the much less shagreened surface of the abdominal terga (Müller-Liebenau 1971, 1974).
Etymology.This species occurs in Israel, the Palestinian Authority, and apparently also in Jordan.Its name reflects our yearning for regional peace.
Distribution and ecology.Baetis pacis is distributed mainly in the tributaries of the Jordan River (i.e., Senir, Dan and Iyyon; Figure 2A) but is occasionally encountered in small numbers in smaller Golan streams (Figure 2E) and in the vicinity of the Sea of Galilee (e.g., Arbel Stream).Based on details in Samocha (1972), it may also occur in the Hermon (Panyas) and Ammud streams.An isolated population is found in Perat Stream (Wadi Qelt; Figure 2G).Alhejoj et al. (2014) referred to "Baetis sp." from Wadi Hisban in Jordan, about 50km east of Perat Stream.Additional study may confirm that this population indeed belongs to B. pacis.The Israeli populations probably represent the southeastern limit of distribution for the B. lutheri species group.The distribution of B. pacis is limited to small-and medium-sized streams with moderate water flow and stony substrate.While water temperature in its habitats may vary, low salinity (< 300 ppm) and high oxygen concentration (>85%) are more important for the species.Mature nymphs were found mostly in spring (April-May) and fall (October-November).Koch, 1981Figures 4F, 16-17 "Baetis L34": Samocha 1972: 6, pl XX, figs 1-8. Baetis samochai: Koch 1981: 121-128, figs 1-14;Koch 1988: 94;Tanatmış 1999;Kazancı 2001;Salur et al. 2016: 74;Bojková et al. 2018: 95.Notes.As the original description (Koch 1981) was superficial, lacked important diagnostic characters, and some of the drawings were of poor quality, we provide a more detailed description below.

Differential diagnosis.
Baetis samochai is well distinguishable by the following combination of characters: canines of both mandibles with a very broad outer tooth; maxillary palp longer than galea-lacinia; dorsal margin of femora with abundant small, strong setae; elongate body; long gills (about twice the length of following abdominal segment); distal margin of terga with needle-like spines; abdominal colouration yellowish brown with whitish, central longitudinal stripe.
Head.Dorsal surface of labrum (Figure 16B; fig. 5 in Koch 1981) with scattered fine setae and seta bases, one median pair of long setae and distolateral arc of setae composed of 7-8 long, simple, stout setae; lateral margin with 4-6 small, fine setae; ventral surface with 4-5 small, stout setae laterodistally; distal margin with row of ca. 30 fine, long, feathered setae.Right and left mandibles with two sets of denticles relatively deeply cleft (Figure 16C, E; Koch 1981: figs 6, 7), outer denticle very broad, constituting most of outer set.Maxilla (Figure 16F; Koch 1981: fig.10) with four broad teeth; lacinia with two rows of setae, one row with abundant small setae ending with stouter and longer setae, second row with two serrated, stout dentisetae; base of lacinia with row of five stout setae; one seta perpendicular to lacinia margin; palpus 2-segmented, segment II longer than segment I, exceeding galea-lacinia in length; segment II with thin setae and apical nipple, apical scale absent.Labium (Figure 16G): palpus 3-segmented; segment II with slightly developed distolateral protuberance; segment III symmetrical, rounded.
Abdomen.Distal margin of terga with slender triangular spines, more than twice longer than broad (Figure 17C; space between spines wider than originally illustrated by Koch 1981: fig.10).Gills elongate with developed tracheation (Figure 17D, E; Koch 1981: fig.14); gill IV twice as long as following tergum.Paraproct (Figure 17F) with abundant seta bases, few hair-like setae and rarely pointed submarginal spatulas; margin with 16-19 long, triangular spines; postero-lateral extension with fewer seta bases, margin with 15-20 triangular spines almost as long as those of paraproct.
Distribution and ecology.Baetis samochai is known from Israel, Lebanon, Syria (Koch 1981(Koch , 1988)), Turkey (Tanatmış 1999;Kazancı 2001;Salur et al. 2016), and Iran (Bojková et al. 2018).In Israel it was recorded by Samocha (1972) exclusively from the northern Golan Heights, but we found numerous populations throughout the Golan Heights, Hula Valley, and the Upper Jordan River and its tributaries.This species may have been overlooked by Samocha or has become more abundant since his study.Unlike most Baetis species, B. samochai was reported from lotic as well as lentic habitats, with abundant aquatic vegetation (Koch 1981).Indeed, we found this species in Israel in diverse ecological niches, including ponds, marshes and streams with moderate or rapid currents (Figure 2A, B, D, E).It is most typically found in calm microhabitats with abundant vegetation along waterbody margins.

Concluding remarks
The present work is the first thorough taxonomic study on Israeli mayflies to have been conducted for more than two decades, and increases the Israeli mayfly fauna by 35%.(Koch 1981) and Jordan (Gattolliat et al. 2012), respectively, and the authors predicted that they will also be found in Israel based on their distribution patterns and on comments made in Samocha's unpublished thesis (1972).Species distribution patterns and the regional hydrography suggest that at least some of the Israeli species are also present in Lebanon and Syria.
Our study was based exclusively on recent collections (2014-2018) by us or by colleagues.Comparison of these newly collected specimens to old material collected by Samocha (early 1970s) and Ortal (1980s-1990s) was impossible due to its poor condition.The collecting details mentioned by Samocha (1972) suggest that our sampling efforts were comprehensive and accurately represent the Israeli fauna.Nevertheless, it is possible that additional Baetis species will be found when the old collections are sorted and fully identified.Moreover, our molecular analysis implies that cryptic Baetis species are yet to be discovered in Israel.
The highest diversity of Baetis species in Israel, as well as for Israeli mayflies in general, is found in the northern stream system (Figure 1), including the upper Jordan River, its tributaries (the Hermon, Senir, Dan, and Iyyon streams) and smaller streams and brooks in the Golan Heights.This pattern can be attributed to the combination of temperate climate, relatively high precipitation, and moderate human disturbance.
Except for the fairly abundant B. monnerati, most of the Israeli Baetis species face threats that result from the frail status of their habitats.Severe water shortage in recent years affects mainly the northern water courses of Israel, and loss of aquatic habitats due to development or pollution is evident throughout the country.Sensitive Baetis populations are likely to degrade accordingly, a trend that has probably already began.Isolated populations of B. pacis (Perat Stream) and B. aureus (Yarqon Stream) are probably relicts of a continuous distribution pattern in the past, rendering these populations and their habitats of high conservation value.

Figure 1 .
Figure 1.Sampling sites and Baetis species richness in Israel and the Palestinian Authority.

Figure 2 .
Figure 2. Typical Baetis habitats in Israel and the Palestinian Authority: A Senir Stream, a main source of the Jordan River B Hula nature reserve, a marshland habitat C Keziv Stream, a pristine stream in a forested area in the Upper Galilee D Ateret Fortress, a site in the Upper Jordan River system E Maymon Spring, a small spring-fed brook in the Upper Jordan River system, the Golan Heights F Zippori Stream, a lowland stream in the Lower Galilee G Perat Stream (Wadi Qelt) in the eastern Judean Mountains H Arugot Stream, a desert stream in the arid water system of the Dead Sea.

Figure 6 .
Figure 6.Baetis aureus sp.n., nymph.A foreleg B tarsal claw C abdominal tergum V, surface and distal margin D gill I E gill IV F paraproct plate.

Figure 8 .
Figure 8. Baetis golanensis sp.n., nymph.A foreleg B tarsal claw C abdominal tergum V, surface and distal margin D gill I E gill IV F paraproct plate.

Figure 13 .
Figure 13.Baetis noa sp.n., nymph.A foreleg B tarsal claw C abdominal tergum V, surface and distal margin D gill I E gill IV, costal margin, detail F paraproct plate.

Figure 15 .
Figure 15.Baetis pacis sp.n., nymph.A foreleg B tarsal claw C abdominal tergum V, surface and distal margin D gill I E gill IV F paraproct plate.

Figure 17 .
Figure 17.Baetis samochai, nymph.A foreleg B tarsal claw C abdominal tergum V, surface and distal margin D gill I E gill IV F paraproct plate.

Table 1 .
Intraspecific (bold)and interspecific genetic distances among sequences of the mitochondrial COI gene of the six Israeli Baetis species (mean, minimum-maximum).
13.5%-13.5%27.0%-27.1%15.2%-16.0%14.3%-15.2%14.3%-14.3%0.0%-0.0%Figure 3.A Maximum Likelihood phylogenetic reconstruction based on sequences of the mitochondrial COI gene obtained from Israeli and related species.The validity of six Israeli species is confirmed and strongly supported.Gray shaded clades represent cryptic species that are morphologically indistinguishable from the species described here.Bootstrap values above 70% are indicated next to the nodes.
The six Baetis species occurring in Israel represent four species groups sensu Müller-Liebenau (1969): the Baetis rhodani group (represented by B. noa), the B. lutheri group (B.golanensis and B. pacis), the B. buceratus group (B.monnerati), and the B. vernus group (B.samochai).Baetis aureus may belong in either of the latter two groups.Baetis samochai and B. monnerati were described from Syria