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Research Article
Croatian mayflies (Insecta, Ephemeroptera): species diversity and distribution patterns
expand article infoMarina Vilenica, Jean-Luc Gattolliat§, Zlatko Mihaljević|, Michel Sartori§
‡ University of Zagreb, Petrinja, Croatia
§ Museum of Zoology, Lausanne, Switzerland
| University of Zagreb, Zagreb, Croatia
Open Access

Abstract

Knowledge of the mayfly biodiversity in the Balkan Peninsula is still far from complete. Compared to the neighbouring countries, the mayfly fauna in Croatia is very poorly known. Situated at the crossroads of central and Mediterranean Europe and the Balkan Peninsula, Croatia is divided into two ecoregions: Dinaric western Balkan and Pannonian lowland. Mayflies were sampled between 2003 and 2013 at 171 sites, and a total of 66 species was recorded. Combined with the literature data, the Croatian mayfly fauna reached a total of 79 taxa. Of these, 29 species were recorded for the first time in Croatia while 15 species were not previously recorded in Dinaric western Balkan ecoregion. Based on the mayfly assemblage, sampling sites were first structured by ecoregion and then by habitat type. In comparison with the surrounding countries, the Croatian mayfly fauna is the most similar to the Hungarian and Bosnian fauna. Some morphologically interesting taxa such as Baetis cf. nubecularis Eaton, 1898 and Rhithrogena from the diaphana group were recorded. Ephemera cf. parnassiana Demoulin, 1958, the species previously recorded only from Greece, was also recorded.

Keywords

Ephemeroptera, species list, biodiversity, Balkan Peninsula

Introduction

Mayflies (Ephemeroptera) have a worldwide distribution, being absent only from Arctic region, Antarctica and some remote oceanic islands (Barber-James et al. 2008). According to the literature (Bauernfeind and Soldán 2012), 369 species are recorded for Europe and North Africa. Mayflies are a merolimnic insect order (i.e. with aquatic larval stages and terrestrial adults) that plays a critical role in running and standing waters where they hold an important position in secondary production, as an important food source for diverse freshwater and terrestrial predators. In recent decades, human impacts on the distribution and abundance of many aquatic insects, including mayflies, are becoming more and more evident. During the 20th century, increasing industrialisation, population growth, overexploitation of natural resources and different types of pollutions have greatly impacted many European freshwater ecosystems, and also endangering the species inhabiting them (Brittain and Sartori 2009). Highly sensitive, confronted with habitat alteration, mayfly species are among the first to disappear. Therefore they are important indicators of freshwater health and widely used in bio-monitoring programmes over the world (Elliott et al. 1988, Sartori and Brittain 2015). The knowledge of the mayfly biodiversity in the Balkan Peninsula is still far from complete. Moreover, many taxa lack appropriate morphological descriptions for the larval and/or adult stages. The mayfly fauna in Croatia is no exception. Published data on Croatian mayflies are generally part of diverse limnological studies (e.g. Matoničkin 1959, 1987, Matoničkin and Pavletić 1961, 1967, Filipović 1976, Habdija and Primc 1987, Habdija et al. 1994, 2004) in which mayflies were investigated only as part of the overall macroinvertebrate fauna. In most studies, identification tools are generally not cited, thus the accuracy of mayfly species identification is questionable. In summary, 50 mayfly species were recorded from Croatia (Bauernfeind and Soldán 2012, Kovács and Murányi 2013, Ćuk et al 2015). In comparison with the number of species recorded in the neighbouring countries, i.e. 68 in Slovenia, 106 in Italy, and 93 in Hungary (Bauernfeind and Soldán 2012), it can be assumed that the Croatian mayfly fauna has been underestimated to date.

Studies on distribution and biodiversity are of crucial importance in determining the conservation status of certain species and in investigating factors that influence that diversity (de Silva and Medellín 2001). Therefore, knowledge of the mayfly faunal composition, seasonal dynamics, distribution, ecology, biogeography and especially their sensitivity as bio-indicators can enable high-quality classification and protection of Croatian freshwater habitats.

Materials and methods

This research is based on recent mayfly studies conducted in the last decade (2003–2013). The results of field studies were then combined with the literature data given in Bauernfeind and Soldán (2012), Kovács and Murányi (2013) and Ćuk et al. (2015), for the purpose of obtaining a comprehensive checklist of the Croatian mayfly fauna.

Sampling and laboratory methods

Croatia is a relatively small country situated at the crossroads of Central and Mediterranean Europe and Balkan Peninsula, and is divided into two ecoregions: Dinaric western Balkan (ER5) and Pannonian lowland (ER11) (Illies 1978). Specimens were collected in lotic and lentic freshwater habitats throughout the Croatian territory (Fig. 1). Additionally, specimens housed in the collection of the Slovene National History Museum were identified.

Figure 1.

Map of the mayfly fauna sampling sites, Croatia (See Table 1 for codes).

The list of the 171 sampling site names with number codes (site ID), altitude, latitude and longitude is presented in Table 1 as well as on the map (Fig. 1). Larvae were sampled using a Surber sampler and hand net, adults using hand nets and pyramidal emergence traps.

The list of the sampling sites in Croatia. Ecoregions are taken from Illies (1978); Dinaric western Balkan (5) and Pannonian lowland (11). BS = Black Sea Basin; AS = Adriatic Sea Basin.

Site ID Sampling site Altitude Longitude Latitude Ecoregion Basin
1 Karašica River, Valpovo 85 N45°37'44" E18°27'28" 11 BS
2 Vučica River, Valpovo 85 N45°38'14" E18°25'09" 11 BS
3 Čarna channel, Tikveš, near Bilje 85 N45°40'23" E18°50'46" 11 BS
4 Veličanka River, Mihaljevci 155 N45°21'36" E17°40'54" 11 BS
5 Sava River, Slavonski Brod 85 N45°07'35" E18°02'18" 11 BS
6 Sava River, Štitar 80 N45°05'47" E18°37'38" 11 BS
7 Sutla River, Klanjec 160 N46°02'46" E15°43'49" 11 BS
8* Drava River, Varaždin 170 N46°19'50" E16°20'22" 11 BS
9 Drava River, Čakovec, left drainage ditch 165 N46°18'49" E16°27'49" 11 BS
10 Drava River, Dubrava, right drainage ditch 145 N46°18'54" E16°42'15" 11 BS
11 Stream, Trakošćan 275 N46°15'44" E15°56'30" 11 BS
12 Stiper stream, Ljubešćica, Kalnik Mountain 185 N46°09'04" E16°22'18" 11 BS
13 Bliznec stream, Medvednica Mountain 380 N45°52'38" E15°58'33" 11 BS
14 Veliki potok stream, Medvednica Mountain, Mikulići 300 N45°51'29" E15°56'08" 11 BS
15 Kraljevec stream, Medvednica Mountain 565 N45°52'48" E15°56'28" 11 BS
16 Sitnik spring, Žumberak-Samoborsko Gorje Mountain 745 N45°44'40" E15°32'39" 11 BS
17 Slapnica stream, Žumberak-Samoborsko Gorje Mountain 290 N45°44'12" E15°29'29" 11 BS
18* Kupa River, Sisak 90 N45°28'32" E16°22'37" 11 BS
19 Sava River, Rugvica 100 N45°44'01" E16°13'11" 11 BS
20 Sava River, Mlaka 90 N45°14'14" E17°01'11" 11 BS
21 Sava River, Zagreb, bridge 110 N45°47'03" E16°00'10" 11 BS
22 Bregana River, Jarušje 560 N45°46'21" E15°34'36" 11 BS
23 Stream, Mečenčani 180 N45°17'07" E16°25'53" 11 BS
24 Stream Zeleni dol, Hrastovica/Hrvatski Čuntić 160 N45°21'51" E16°16'15" 11 BS
25 Pond Zeleni dol, Hrastovica/Hrvatski Čuntić 160 N45°21'51" E16°16'18" 11
26 Petrinjčica River, Prnjavor Čuntićki 150 N45°21'05" E16°16'57" 11 BS
27 Petrinjčica River, Tješnjak, bridge 150 N45°22'52" E16°17'11" 11 BS
28 Utinja River, Križ Hrastovački 140 N45°25'15" E16°14'32" 11 BS
29 Žirovnica River, Donja Ljubina 135 N45°05'39" E16°17'39" 11 BS
30 Moštanica stream, Moštanica 155 N45°21'55" E16°21'06" 11 BS
31 Sunja River, Rakovac 120 N45°18'40" E16°32'33" 11 BS
32 Sunja River, Donji Kukuruzari 150 N45°16'01" E16°29'14" 11 BS
33 Kupa River, Brest 90 N45°26'56" E16°15'38" 11 BS
34 Kupa River, Bubnjarci 135 N45°38'42" E15°21'24" 5 BS
35 Una River, Hrvatska Kostajnica 105 N45°13'37" E16°32'22" 11 BS
36 Glina River, Marinbrod 100 N45°23'19" E16°08'20" 11 BS
37 Glina River, Cerjak 110 N45°21'27" E16°04'58" 11 BS
38 Čemernica stream, Topusko 125 N45°19'08" E15°57'30" 11 BS
39 Sava River oxbow, Mužilovčica 90 N45°23'23" E16°40'37" 11 BS
40* Sava River, Martinska Ves 95 N45°35'09" E16°22'14" 11 BS
41* Sava River, Desno Trebarjevo 95 N45°35'56" E16°20'43" 11 BS
42* Sava River, Krapje 90 N45°18'10" E16°49'23" 11 BS
43 Sava River, Lukavec Posavski 90 N45°24'36" E16°31'03" 11 BS
44 Sava River, Drenov bok 90 N45°15'58" E16°50'04" 11 BS
45 Mire Plavnica, Šatornja 125 N45°19'58 E16°00'26" 11
46 Javošnica stream, Donji Javoranj 140 N45°07'14" E16°21'44" 11 BS
47 Odra River, Sisak 95 N45°29'54" E16°21'04" 11 BS
48 Zrinčica River, Zrin 240 N45°11'41" E16°22'13" 11 BS
49 Čatlan River, Gornja Oraovica 170 N45°09'26" E16°25'03" 11 BS
50 Spring Izvor bijele stijene Križ, Župić 135 N45°25'44" E16°13'52" 11 BS
51 Šanja River, Gora 140 N45°25'08" E16°11'42" 11 BS
52 Radonja River, Vojnić 140 N45°19'26" E15°41'55" 11 BS
53 Lonja River, Brežnički Hum 200 N46°07'34" E16°17'18" 11 BS
54 Lonja River, Breznica 180 N46°04'11" E16°18'07" 11 BS
55 Mrežnica River, Generalski stol 140 N45°22'05" E15°24'55" 5 BS
56 Mrežnica River, Duga Resa 120 N45°27'31" E15°29'38" 5 BS
57 Dretulja River, Plaški, spring 390 N45°04'31" E15°20'32" 5 BS
58 Dretulja River, Plaški, middle reach 375 N45°05'06" E15°21'56" 5 BS
59 Trupinjska rijeka River, Keserov potok 150 N45°17'04" E15°37'28’ 5 BS
60* Gojačka Dobra River, Gorinci, downstream from the waterfall 160 N45°21'10" E15°20'44" 5 BS
61* Gojačka Dobra River, Gorinci, waterfall above the dam 160 N45°20'60" E15°20'45" 5 BS
62* Gojačka Dobra River, Tomašići 145 N45°22'33" E15°21'18" 5 BS
63 Bukovska Dobra River, Turkovići 340 N45°16'59" E15°10'49" 5 BS
64 Ribnjak stream, Trošmarija 195 N45°19'43" E15°16'25" 5 BS
65 Vitunjčica stream, Vitunj 340 N45°17'01" E15°09'48" 5 BS
66 Bistrica stream, Bistrac 230 N45°16'27" E15°17'28" 5 BS
67 Sušik stream, Drežnica 465 N45°08'44" E15°04'41" 5 BS
68 Bračana stream, Škuljari 45 N45°24'57" E13°55'36" 5 AS
69 Rečica stream, Pengari 90 N45°23'21" E13°59'13" 5 AS
70 Draga River, Selca 160 N45°23'36" E13°59'46" 5 AS
71 Račićki potok stream, Juradi 50 N45°20'17" E13°57'20" 5 AS
72 Mirna River, Kotli 155 N45°22'06" E14°01’ 5 AS
73 Jadova River, Gornja Ploča 610 N44°27'03" E15°38'58" 5 AS
74 Obsenica stream, near Lovinac 560 N44°21'09" E15°40'36" 5 AS
75 Ričica stream, Ričice 560 N44°20'23" E15°45'08" 5 AS
76 Lika River, Lički Ribnik 565 N44°29'13" E15°27'38" 5 AS
77 Gacka River, Ličko Lešće 450 N44°48'46" E15°19'18" 5 AS
78 Gacka River,Prozor 450 N44°50'23" E15°15'21" 5 AS
79* Bijela rijeka River, NP Plitvice Lakes, upper reach 715 N44°50'04" E15°33'33" 5 BS
80* Bijela rijeka River, NP Plitvice Lakes, spring 760 N44°49'56" E15°33'22" 5 BS
81* Crna rijeka River, NP Plitvice Lakes, spring 710 N44°49'43" E15°36'49" 5 BS
82* Crna rijeka River, NP Plitvice Lakes, upper reach 680 N44°50'10" E15°36'30" 5 BS
83* Crna rijeka River, NP Plitvice Lakes, lower reach 670 N44°50'22" E15°35'59" 5 BS
84* Korana River, NP Plitvice Lakes 390 N44°55'33" E15°37'09" 5 BS
85* Plitvica stream, NP Plitvice Lakes 555 N44°54'08" E15°36'27" 5 BS
86* Tufa barrier Novakovića Brod, NP Plitvice Lakes 510 N44°54'07" E15°36'38" 5 BS
87* Tufa barrier Labudovac, NP Plitvice Lakes 630 N44°52'17" E15°35'59" 5 BS
88* Tufa barrier Kozjak-Milanovac, NP Plitvice Lakes 545 N44°53'39" E15°36'32" 5 BS
89* Kozjak Lake, NP Plitvice Lakes 555 N44°53'18" E15°36'38" 5 BS
90* Prošće Lake, NP Plitvice Lakes 665 N44°51'51" E15°36'06" 5 BS
91* Ciginovac Lake, NP Plitvice Lakes 640 N44°52'22" E15°35'51" 5 BS
92* Kaluđerovac Lake, NP Plitvice Lakes 540 N44°54'05" E15°36'41" 5 BS
93 Suha Ričina stream, Jurandvor, Krk island 20 N44°58'38" E14°43'52" 5 AS
94 Zeleni vir, Skrad 540 N45°25'25" E14°53'53" 5 BS
95 Curak stream, Zeleni vir 330 N45°25'37" E14°53'33" 5 BS
96 Veli potok stream, Dobrinj, Krk island 35 N45°08'06" E14°35'43" 5 AS
97 Kupica River spring, Mala Lešnica, NP Risnjak 270 N45°25'48" E14°51'07" 5 BS
98 Mijića vrelo stream, Mijići 60 N44°09'37" E15°52'38" 5 AS
99 Krupa River, Krupa 130 N44°11'34" E15°54'34" 5 AS
100 Krupa River, Kudin bridge 90 N44°11'16" E15°50'44" 5 AS
101 Pond, Zvjerinac 245 N43°56'45" E16°12'56" 5
102 Jaruga stream, Jelavića bridge, Zmijavci 260 N43°24'46" E17°15'09" 5 AS
103 Otuča River, Deringaj, Kijani 615 N44°21'02" E15°52'34" 5 AS
104 Vransko Lake, main channel, Biograd 0 N43°56'20" E15°30'59" 5 AS
105 Vransko Lake, Biograd, Drage 5 N43°53'44" E15°33'07" 5 AS
106 Krka River, Roški slap waterfall, NP Krka 75 N43°54'23" E15°58'30" 5 AS
107 Visovac Lake, NP Krka 50 N43°51'38" E15°58'55" 5 AS
108 Brljan Lake, NP Krka 205 N44°00'30" E16°02'41" 5 AS
109* Kosovčica River, upper reach, Vučenovići 230 N43°58'30" E16°12'45" 5 AS
110* Kosovčica River, lower reach, Biskupija 220 N44°00'26" E16°12'52" 5 AS
111 Krka River, Knin 220 N44°01'56" E16°11'26" 5 AS
112 Krka River, upstream of Kosovčica river mouth, Knin 220 N44°02'24" E16°13'42" 5 AS
113 Krka River, downstream of Kosovčica river mouth, Knin 215 N44°01'41" E16°12'48" 5 AS
114 Orašnica River, Knin 225 N44°01'56" E16°12'04" 5 AS
115 Zrmanja River, Mokro polje, Prkos 200 N44°05'31" E16°02'00" 5 AS
116 Zrmanja River, Vekići 130 N44°06'06" E15°56'41" 5 AS
117 Zrmanja River, Palanka 270 N44°08'23" E16°04'25" 5 AS
118 Zrmanja River, Muškovci, Berberi buk 20 N44°11'50" E15°46'07" 5 AS
119 Zrmanja River, Kravlja Draga, bridge 240 N44°05'50" E16°04'30" 5 AS
120 Zrmanja River, Žegar, bridge 60 N44°09'10" E15°53'08" 5 AS
121 Zrmanja River, Draga 55 N44°09'50" E15°50'43" 5 AS
122 Lopuško vrelo stream, Lake 220 N44°01'11" E16°13'21" 5 AS
123 Krčić River, Kovačić 315 N44°02'19" E16°16'42" 5 AS
124 Krčić River, Mlinica 380 N44°01'38" E16°19'25" 5 AS
125 Šarena jezera lake, Biskupija 220 N44°01'36" E16°13'22" 5
126 Čikola River, near Rakići 100 N43°50'13" E16°04'25" 5 AS
127 Čikola River, Otavice 270 N43°50'36" E16°15'25" 5 AS
128 Vrba River, Vrba 425 N43°43'21" E16°23'58" 5 AS
129 Vrba River, Čavoglave 290 N43°47'28" E16°18'52" 5 AS
130 Butižnica River, Knin 220 N44°02'44" E16°11'39" 5 AS
131 Brodic stream, Markovac, Biskupija 250 N43°57'03" E16°15'00" 5 AS
132 Karakašica, Karakašica 320 N43°43'04" E16°38'19" 5 AS
133 Boggy seepages, Bruvno, Gračac 690 N44°23'15" E15°53'08" 5
134 Ričina stream, Proložac 400 N43°29'20" E17°09'11" 5 AS
135* Cetina River, Spring Glavaš 385 N43°58'36" E16°25'48" 5 AS
136 Grab River, Spring 330 N43°38'24" E16°46'20" 5 AS
137* Cetina River, Preočki most bridge 370 N43°57'59" E16°25'53" 5 AS
138* Cetina River, Crveni most bridge 365 N43°57'35" E16°25'46" 5 AS
139* Cetina River, Obrovac Sinjski 300 N43°43'58" E16°41'11" 5 AS
140* Cetina River, Trilj1 295 N43°36'54" E16°43'42" 5 AS
141* Cetina River, Čikotina lađa 250 N43°31'58" E16°44'42" 5 AS
142* Cetina River, Radmanove mlinice 15 N43°26'19" E16°45'06" 5 AS
143* Cetina River, Trilj2 295 N43°36'19" E16°43'28" 5 AS
144 Cetina River, Peruča Reservoir 360 N43°47'45" E16°35'32" 5 AS
145 Cetina River, Zadvarje 205 N43°26'02" E16°53'18" 5 AS
146* Ruda River, spring 295 N43°40'07" E16°47'39" 5 AS
147* Ruda River, upper reach 320 N43°40'06" E16°47'28" 5 AS
148 Cetina River tributary stream, Vukovići, Paško polje 370 N43°58'06" E16°25'07" 5 AS
149 Cetina River tributary stream, Kotluša, Paško polje 375 N43°56'54" E16°24'06" 5 AS
150 Jadro River 1, Solin 10 N43°32'23" E16°29'45" 5 AS
151 Matica River, Vrgorac 60 N43°12'21" E17°23'46" 5 AS
152 Matica River, Umčani 40 N43°10'28" E17°22'32" 5 AS
153 Stinjevac spring, Dusina 30 N43°10'29" E17°25'02" 5 AS
154 Cetina River, Čitluk 300 N43°44'48" E16°39'49" 5 AS
155 Vukovića vrilo spring, Bitelići, Hrvace 505 N43°49'12" E16°37'28" 5 AS
156 Ljuta River, spring 90 N42°32'20" E18°22'46" 5 AS
157 Ljuta River, upper reach, Donja Ljuta 60 N42°32'05" E18°22'39" 5 AS
158 Vodovađa stream, Palje Brdo 110 N42°30'29" E18°24'34" 5 AS
159 Konavočica River, near Karasovići 110 N42°30'19" E18°24'37" 5 AS
160 Stream, near Zastolje 75 N42°31'17" E18°23'31" 5 AS
161 Stream, near Brajkovići 90 N42°31'49" E18°23'14" 5 AS
162 Vrljika River, Kamenmost 265 N43°25'52" E17°11'42" 5 AS
163 Vrljika River, Kapuše 270 N43°26'33" E17°10'32" 5 AS
164 Jarun Lake, Zagreb 110 N45°46'47" E15°55'17" 11 BS
165 Stream under the village Beram 290 N45°15'10" E13°54'18" 5 AS
166 Spring by the church, Stajnica, Porkulabi 500 N45°02'31" E15°14'18" 5 AS
167 Danube River, Ilok 75 N45°13'49" E19°23'26" 11 BS
168 Ljubica stream, Baške Oštarije, Linići, Velebit Mountain 910 N44°31'37" E15°09'41" 5 AS
169 Spring by the church, Slano 15 N42°47'01" E17°53'26" 5 AS
170 Spring by the sea, Dubrovnik, Mali Zaton 5 N42°42'06" E18°02'40" 5 AS
171 Tounjčica stream,Tounj 220 N45°14'56" E15°20'04" 5 BS

Mayflies were sampled in every season at 34 sites, while at the remainder of sites, sampling was usually performed only once between April and September. Specimens were stored in 80% ethanol and identified in the lab using a stereomicroscope and microscope. A reference collection was made by preparing permanent slide mounts of identified species. Larvae were treated with 10% KOH and 99% acetic acid to remove all muscle parts. Mouth parts, legs, gills, thorax, abdomen, paraproct plate in Baetidae and cerci, necessary for the species identification, were fixed in Euparal and examined under a microscope. Adult specimens were mostly identified by the imaginal male genitalia. The collected material (larvae and adult specimens) was identified using Müller-Liebenau (1969), Elliott and Humpesch (1983), Malzacher (1984), Elliott et al. (1988), Studemann et al. (1992), Haybach (1999), Bauernfeind and Humpesch (2001), combined with numerous publications with species descriptions (e.g. Tomka and Rasch 1993).

Data analysis

All recorded specimens were included in the Croatian mayfly species list. Data for the sites with the same sampling effort were statistically analysed using the PRIMER 6 software package (Clarke and Warwick 2001). As such, only 34 sampling sites were compared out of the total 171 (Table 1). These sites were sampled in all seasons, at the available microhabitats and they represent habitats in each ecoregion and each sea basin. Species diversity, evenness, and similarity between sites with respect to the mayfly composition and abundance were determined by the Shannon-Weaver and Simpson indices. For estimation of similarity and differences in the mayfly community composition, cluster analysis was used. Similarity among sites was determined using the Bray-Curtis similarity index. SIMPER (Similarity Percentage) was used to assess which taxa are primarily responsible for the similarities between the sites of the same habitat type. The Croatian mayfly species richness was compared with the surrounding countries (Bosnia & Herzegovina, Hungary, Slovenia, Italy) by compiling species list for these countries taken from Bauernfeind and Soldán (2012) and the Sørensen Index of Similarity was calculated.

Results

Species richness

In total, 79 mayfly taxa (Table 2) were recorded for Croatia. Of the 171 sites (55 in ER11, 116 in ER5) investigated during this study (Table 1), 66 taxa were sampled, of which 29 were recorded for the first time (Table 2). The presence of 13 (16%) previously recorded species could not be confirmed (Table 2). The most diverse genera were Baetis Leach, 1815 and Ecdyonurus Eaton, 1868 both with 11 species. Baetis rhodani (Pictet, 1843) and Serratella ignita (Poda, 1761) were the most widely distributed species, present in 83 and 76 sampling sites, respectively. Fourteen species were recorded at only one sampling site: Cloeon simile Eaton, 1870, Procloeon nana (Bogoescu, 1951), Caenis pusilla Navàs, 1913, Ephemera cf. parnassiana Demoulin, 1958, Leptophlebia vespertina (Linnaeus, 1758), Ecdyonurus vitoshensis Jacob & Braasch, 1984, Ecdyonurus zelleri (Eaton, 1885), Electrogena mazedonica (Ikonomov, 1954), Heptagenia coerulans Rostock, 1878, H. flava Rostock, 1878, H. longicauda (Stephens, 1835), Rhithrogena iridina (Kolenati, 1839), Rh. gr. diaphana and Rh. semicolorata (Curtis, 1834).

Croatian mayfly fauna.

Mayfly taxa Ecoregion Habitat type Basin
Ametropodidae
Ametropus fragilis Albarda, 1878 11 3 BS
Ameletidae
Ameletus inopinatus Eaton, 1887 - - -
Metreletus balcanicus (Ulmer, 1920) - - -
Siphlonuridae
Siphlonurus armatus (Eaton, 1870) - - -
Siphlonurus croaticus Ulmer, 1920 11 2,3,4 AS
Siphlonurus lacustris (Eaton, 1870) 5, 11 2,3 BS, AS
Baetidae
Alainites muticus (Linnaeus, 1758) 5 2,3,4 BS, AS
Baetis alpinus (Pictet, 1843) 5, 11 1,2,3 BS
Baetis buceratus Eaton, 1870 11 3 BS
Baetis fuscatus (Linnaeus, 1761) 5, 11 3 BS
Baetis liebenauae Keffermüller, 1974 5, 11 1,2,3 BS, AS
Baetis lutheri Müller-Liebenau, 1967 5, 11 1,3 BS, AS
Baetis melanonyx (Pictet, 1843) 5 1,2,3 AS
Baetis cf. nubecularis (Eaton, 1898) 5 1,2,3,4 BS
Baetis rhodani (Pictet, 1843) 5, 11 1,2,3,4 BS, AS
Baetis scambus Eaton, 1870 11 3 BS
Baetis tricolor Tshernova, 1928 11 3 BS
Baetis vernus Curtis, 1834 5, 11 3 BS, AS
Baetopus tenellus (Albarda, 1878) 5, 11 2,3 BS
Nigrobaetis niger (Linnaeus, 1761) 5, 11 2,3 BS, AS
Centroptilum luteolum (Müller, 1776) 5, 11 2,3,4,5 BS, AS
Cloeon dipterum (Linnaeus, 1761) 5, 11 2,3,5 BS, AS
Cloeon simile Eaton, 1870 5 5 AS
Procloeon bifidum (Bengtsson, 1912) 5, 11 2,3 BS, AS
Procloeon nana (Bogoescu, 1951) 5 2 AS
Procloeon pennulatum (Eaton, 1870) 5, 11 3,4 BS, AS
Caenidae
Brachycercus harrisellus Curtis, 1834 11 3 BS
Caenis beskidensis Sowa, 1973 5 3 AS
Caenis horaria (Linnaeus, 1758) 5, 11 3,4,5 BS, AS
Caenis macrura Stephens, 1835 5, 11 3 BS, AS
Caenis pusilla Navàs, 1913 5 3 BS
Caenis rivulorum Eaton, 1884 11 3 BS
Caenis robusta Eaton, 1884 11 2,3,5 BS
Ephemerellidae
Ephemerella mucronata (Bengtsson, 1909) 5, 11 2,3 BS, AS
Serratella ignita (Poda, 1761) 5, 11 1,2,3,4 BS, AS
Torleya major (Klapalek, 1905) 5, 11 2,3,4 BS, AS
Ephemeridae
Ephemera danica Müller, 1764 5, 11 2,3,4,5 BS, AS
Ephemera glaucops Pictet, 1843 - - -
Ephemera lineata Eaton, 1870 5 2,3,5 AS
Ephemera cf. parnassiana Demoulin, 1958 5 2 AS
Ephemera vulgata Linnaeus, 1758 5, 11 2,3,5 BS, AS
Ephemera zettana Kimmins, 1937 5 2,3 AS
Palingeniidae
Palingenia longicauda (Olivier, 1791) - - -
Polymitarcyidae
Ephoron virgo (Olivier, 1791) - - -
Leptophlebiidae
Choroterpes picteti (Eaton, 1871) - - -
Habroleptoides confusa Sartori and Jacob, 1986 5, 11 2,3 BS, AS
Habrophlebia fusca (Curtis, 1834) 5, 11 1,2,3 BS, AS
Habrophlebia lauta Eaton, 1884 5, 11 2,3,5 BS, AS
Leptophlebia vespertina (Linnaeus, 1758) 5 2,5 BS, AS
Paraleptophlebia submarginata (Stephens, 1835) 5, 11 2,3,4 BS, AS
Paraleptophlebia werneri Ulmer, 1920 5 2,5 BS
Oligoneuriidae
Oligoneuriella rhenana (Imhoff, 1852) 11 3 BS
Potamanthidae
Potamanthus luteus (Linnaeus, 1767) 11 3 BS
Heptageniidae
Ecdyonurus aurantiacus (Burmeister, 1839) - - -
Ecdyonurus dispar (Curtis, 1834) 5 2,3 BS, AS
Ecdyonurus insignis (Eaton, 1870) 5, 11 3 BS, AS
Ecdyonurus macani Thomas & Sowa, 1970 5, 11 3 BS, AS
Ecdyonurus siveci Hefti, Tomka & Zurwerra, 1986 - - -
Ecdyonurus starmachi Sowa, 1971 5, 11 2,3 BS, AS
Ecdyonurus submontanus Landa, 1969 5 3 BS
Ecdyonurus torrentis Kimmins, 1942 5 2,3 BS, AS
Ecdyonurus venosus (Fabricius, 1775) 5 2,3 AS
Ecdyonurus vitoshensis Jacob & Braasch, 1984 11 2 BS
Ecdyonurus zelleri (Eaton, 1885) 11 2 BS
Electrogena affinis (Eaton, 1883) 5 2,3 AS
Electrogena lateralis (Curtis, 1834) 5, 11 2,3,4 BS, AS
Electrogena mazedonica (Ikonomov, 1954) 5 3 AS
Electrogena ujhelyii (Sowa, 1981) 5, 11 1,2 BS, AS
Epeorus assimilis Eaton, 1885 5, 11 1,2,3 BS, AS
Heptagenia coerulans Rostock, 1878 11 3 BS
Heptagenia flava Rostock, 1878 11 3 BS
Heptagenia longicauda (Stephens, 1835) 5 3 BS
Heptagenia sulphurea (Müller, 1776) 11 3 BS
Kageronia fuscogrisea (Retzius, 1783) - - -
Rhithrogena braaschi Jacob, 1974 5 1,2,3 BS, AS
Rhithrogena gr. diaphana 11 3 BS
Rhithrogena germanica Eaton, 1885 - - -
Rhithrogena iridina (Kolenati, 1839) 11 2 BS
Rhithrogena semicolorata (Curtis, 1834) 11 2 BS

Approximately half of the species (30) were present in both ecoregions. A total of 50 species was recorded as present only in the Dinaric western Balkan ecoregion (ER5) and 48 only in the Pannonian lowland ecoregion (ER11) (Table 2). Nearly half the species (32) were recorded in both the Black and Adriatic Sea Basins, while 25 species were recorded only for Black Sea basin and 11 species only for Adriatic Sea basin (Table 2).

The Sørensen Index of Similarity indicated the Croatian mayfly fauna had the greatest similarity with the Hungarian assemblage (Table 3).

Sørensen Index of Similarity between mayfly assemblages for surrounding countries in relation to Croatia. CRO = Croatia, B&H = Bosnia and Herzegovina, I = Italy, SLO = Slovenia, HUN = Hungary.

CRO B&H I SLO
CRO
B&H 64.62
I 55.44 51.89
SLO 61.64 56.67 51.72
HUN 74.85 60.69 54.27 52.17

Mayflies (Insecta, Ephemeroptera) of Croatia

For the distribution data, the following format was used: “Literature data” were mainly taken from Bauernfeind and Soldán (2012), which listed the presence of each species in Croatia but without reference to their exact localities. Two and one species and localities where they were recorded were mentioned in Kovács and Murányi (2013) and Ćuk et al., respectively. “Literature data with new records” corresponds to data obtained as a part of this study but were already published. “New records” are data obtained in this study but were not yet published. For every species, the site ID is listed. All sampling sites and their ID numbers are listed in Table 1.

● New records for the Croatian mayfly fauna

■ Only adults recorded

I. Ametropodidae Bengtsson, 1913

1. Ametropus fragilis Albarda, 1878

Literature data: Drava River, Donji Miholjac (Ćuk et al. 2015)

II. Ameletidae McCafferty, 1991

2. Ameletus inopinatus Eaton, 1887

Literature data: Bauernfeind and Soldán (2012)

3. Metreletus balcanicus (Ulmer, 1920)

Literature data: Bauernfeind and Soldán (2012)

III. Baetidae Leach, 1815

4. Alainites muticus (Linnaeus, 1758)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 79, 80■, 82, 84, 85, 86 (Vilenica et al. 2014)

New records: 68, 70, 115, 150, 158, 160, 161, 162, 163,165, 168

5. Baetis alpinus (Pictet, 1843)

Literature data: Bauernfeind and Soldán (2012)

New records: 13, 15, 57, 63

6. Baetis buceratus Eaton, 1870 ●

New records: 2, 36

7. Baetis fuscatus (Linnaeus, 1761)

Literature data: Bauernfeind and Soldán (2012)

New records: 5, 7, 8, 10, 18, 19, 26, 29, 31, 32, 35, 36, 40, 56, 60, 61, 62

8. Baetis liebenauae Keffermüller, 1974 ●

New records: 1, 2, 9, 10, 35, 36, 37, 62, 98, 109, 110, 111, 112, 113, 122, 128, 131, 134, 139, 140, 141, 143, 151, 152, 153, 162, 171

9. Baetis lutheri Müller-Liebenau, 1967

Literature data: Bauernfeind and Soldán (2012)

New records: 7, 18, 19, 35, 61, 62, 103, 116, 141, 142, 146, 147, 150, 157

10. Baetis melanonyx (Pictet, 1843) ●

New records: 115, 117, 120, 146, 147, 156, 157, 158, 159, 160, 161, 162, 163

11. Baetis cf. nubecularis Eaton, 1898 ●

Literature data with new records: 79, 80, 81, 82, 83, 84, 85, 86, 87 (Vilenica et al. 2014)

12. Baetis rhodani (Pictet, 1843)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 79, 80, 81, 82, 83, 84, 85, 87, 88 (Vilenica et al. 2014)

New records: 9, 10, 13, 15, 16, 23, 24, 26, 28, 29, 30, 31, 32, 34, 35, 48, 50, 51, 53, 59, 61, 62, 63, 64, 65, 66, 68, 70, 77, 78, 98, 99, 100, 103, 109, 110, 112, 113, 114, 115, 116, 117, 118, 120, 122, 123, 124, 128, 131, 132, 134, 135, 137, 138, 139, 140, 141, 142, 146, 147, 148, 149, 153, 157, 158, 159, 160, 161, 162, 163, 166, 169, 170, 171

13. Baetis scambus Eaton, 1870

Literature data: Bauernfeind and Soldán (2012)

New records: 7, 26

14. Baetis tricolor Tshernova, 1928 ●

New records: 20, 43, 44

15. Baetis vernus Curtis, 1834 ●

New records: 7, 9, 10, 36, 38, 53, 54, 76

16. Baetopus tenellus (Albarda, 1878) ●

New records: 19, 64, 94

17. Nigrobaetis niger (Linnaeus, 1761) ●

Literature data with new records: 138

New records: 15, 36, 38, 93, 103, 109, 110, 128, 131

18. Centroptilum luteolum (Müller, 1776)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 84, 85, 86, 87, 88, 89, 90, 91, 92 (Vilenica et al. 2014)

New records: 1, 12, 23, 27, 28, 31, 32, 35, 61, 62, 69, 74, 77, 78, 103, 107, 109, 110, 121, 127, 128, 141, 142, 143, 144, 159

19. Cloeon dipterum (Linnaeus, 1761)

Literature data: Bauernfeind and Soldán (2012)

New records: 1, 5, 20, 24, 35, 37, 39, 41, 43, 44, 45, 46, 47, 60, 67, 78, 101, 103, 104, 105, 121, 125, 127, 128, 129, 152

20. Cloeon simile Eaton, 1870

Literature data: Bauernfeind and Soldán (2012)

New records: 125

21. Procloeon bifidum (Bengtsson, 1912)

Literature data: Bauernfeind and Soldán (2012)

New records: 6, 19, 20, 28, 29, 31, 32, 40, 41, 42, 44, 47, 62, 68, 69, 71, 115, 121, 141

22. Procloeon nana (Bogoescu, 1951) ●

New records: 68

23. Procloeon pennulatum (Eaton, 1870)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 84, 85, 86 (Vilenica et al. 2014)

New records: 26, 27, 61, 127, 129

IV. Caenidae Newman, 1853

24. Brachycercus harrisellus Curtis, 1834

Literature data: Vojlovica River at the bridge of road No. 2, Vojlovica (Kovács and Murányi 2013)

25. Caenis beskidensis Sowa, 1973 ●

New records: 139, 140, 141, 143, 142

26. Caenis horaria (Linnaeus, 1758)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 86, 87, 89, 90, 91, 92 (Vilenica et al. 2014)

New records: 39, 73, 78, 101, 106, 107

27. Caenis macrura Stephens, 1835

Literature data: Bauernfeind and Soldán (2012)

New records: 8, 9, 10, 18, 26, 27, 28, 31, 32, 35, 40, 41, 54, 61, 68, 71, 115, 140, 141, 142, 143

28. Caenis pusilla Navàs, 1913 ●

New records: 62

29. Caenis rivulorum Eaton, 1884 ●

New records: 40, 41

30. Caenis robusta Eaton, 1884 ●

New records: 1, 24, 39, 47

V. Ephemerellidae Klapálek, 1909

31. Ephemerella mucronata (Bengtsson, 1909) ●

New records: 14, 134, 139, 163

32. Serratella ignita (Poda, 1761)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 83, 84, 85, 86, 88 (Vilenica et al. 2014))

New records: 1, 7, 8, 9, 10, 12, 17, 26, 27, 28, 29, 30, 31, 32, 34, 35, 36, 37, 48, 49, 53, 46, 58, 59, 60, 61, 62, 64, 65, 66, 68, 69, 73, 76, 98, 99, 100, 103, 108, 109, 110, 113, 114, 115, 116, 117, 118, 119, 121, 122, 129, 134, 137, 138, 139, 140, 141, 142, 143, 144, 146, 147, 148, 150, 153, 157, 158, 159, 162, 163, 171

33. Torleya major (Klapalek, 1905)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 84, 86 (Vilenica et al. 2014)

New records: 53, 66, 117, 118, 139, 141

VI. Ephemeridae Latreille, 1810

34. Ephemera danica Müller, 1764

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92 (Vilenica et al. 2014)

New records: 8, 14, 17, 23, 27, 28, 30, 33, 48, 49, 53, 59, 60, 61, 63, 64, 66, 68, 95, 100, 115,141, 142

35. Ephemera glaucops Pictet, 1843

Literature data: Bauernfeind and Soldán (2012)

36. Ephemera lineata Eaton, 1870

Literature data: Bauernfeind and Soldán (2012)

New records: 106, 107, 108, 109, 110, 118, 119, 122, 137, 138, 139, 140, 141, 142, 143, 147

37. Ephemera cf. parnassiana Demoulin, 1958 ●

New records: 98

38. Ephemera vulgata Linnaeus, 1758

Literature data: Bauernfeind and Soldán (2012)

New records: 11, 54, 55, 59, 100, 125, 128, 154, 164

39. Ephemera zettana Kimmins, 1937 ● ■

New records: 102, 118, 134, 136, 138, 141, 142, 154, 155

VII. Heptageniidae Needham, 1901

40. Ecdyonurus aurantiacus (Burmeister, 1839)

Literature data: Bauernfeind and Soldán (2012)

41. Ecdyonurus dispar (Curtis, 1834)

Literature data: Bauernfeind and Soldán (2012)

New records: 61, 63, 66, 68, 69

42. Ecdyonurus insignis (Eaton, 1870)

Literature data: Cetina River, between Podgrade and Slime (Kovács and Murányi 2013)

New records: 26, 27, 32, 116, 141, 145

43. Ecdyonurus macani Thomas & Sowa, 1970 ●

New records: 7, 26, 27, 137, 138, 139, 141, 147

44. Ecdyonurus siveci Hefti, Tomka & Zurwerra, 1986

Literature data: Bauernfeind and Soldán (2012)

45. Ecdyonurus starmachi Sowa, 1971 ●

New records: 13, 14, 26, 53, 103, 120

46. Ecdyonurus submontanus Landa, 1969 ●

Literature data with new records: 82, 83 (Vilenica et al. 2014)

47. Ecdyonurus torrentis Kimmins, 1942

Literature data: Bauernfeind and Soldán (2012)

New records: 95, 99, 118, 119, 120

48. Ecdyonurus venosus (Fabricius, 1775)

Literature data: Bauernfeind and Soldán (2012)

New records: 97■, 99, 100, 109, 110, 112, 118, 119, 120, 137, 138, 139, 141, 148, 150, 162

49. Ecdyonurus vitoshensis Jacob & Braasch, 1984

Literature data: Bauernfeind and Soldán (2012)

New records: 12

50. Ecdyonurus zelleri (Eaton, 1885) ●

New records: 53

51. Electrogena affinis (Eaton, 1883) ●

New records: 68, 69, 70

52. Electrogena lateralis (Curtis, 1834)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 86 (Vilenica et al. 2014)

New records: 12, 27, 61, 96, 165

53. Electrogena mazedonica (Ikonomov, 1954) ●

New records: 128

54. Electrogena ujhelyii (Sowa, 1981) ●

New records: 11, 13, 16, 24, 50, 93

55. Epeorus assimilis Eaton, 1885

Literature data: Bauernfeind and Soldán (2012)

New records: 4, 13, 94, 97■, 98, 99, 115, 116, 117, 120, 135■, 137, 138, 141, 142, 146, 147, 156

56. Heptagenia coerulans Rostock, 1878

Literature data: Bauernfeind and Soldán (2012)

New records: 18

57. Heptagenia flava Rostock, 1878

Literature data: Bauernfeind and Soldán (2012)

New records: 167

58. Heptagenia longicauda (Stephens, 1835) ●

New records: 63

59. Heptagenia sulphurea (Müller, 1776)

Literature data: Bauernfeind and Soldán (2012)

New records: 7, 8, 18, 21, 40, 42

60. Kageronia fuscogrisea (Retzius, 1783)

Literature data: Bauernfeind and Soldán (2012)

61. Rhithrogena braaschi Jacob, 1974 ●

Literature data with new records: 79, 80, 81, 82, 83, 85 (Vilenica et al. 2014)

New records: 57, 58, 109, 110, 112, 117, 120, 122, 124, 135, 137, 138, 139, 141, 142, 143, 146, 147, 162, 163

62. Rhithrogena gr. diaphana

New records: 32

63. Rhithrogena germanica Eaton, 1885

Literature data: Bauernfeind and Soldán (2012)

64. Rhithrogena iridina (Kolenati, 1839) ●

New records: 27

65. Rhithrogena semicolorata (Curtis, 1834)

Literature data: Bauernfeind and Soldán (2012)

New records: 53

VIII. Leptophlebiidae Banks, 1900

66. Choroterpes picteti (Eaton, 1871)

Literature data: Bauernfeind and Soldán (2012)

67. Habroleptoides confusa Sartori and Jacob, 1986

Literature data: Bauernfeind and Soldán (2012)

New records: 22, 120, 158

68. Habrophlebia fusca (Curtis, 1834)

Literature data: Bauernfeind and Soldán (2012)

New records: 27, 28, 30, 35, 38, 48, 59, 69, 70, 131, 168, 169

69. Habrophlebia lauta Eaton, 1884

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 82, 83, 85, 90 (Vilenica et al. 2014)

New records: 25, 26, 27, 29, 48, 49, 61, 65, 66, 68, 70, 109, 110

70. Leptophlebia vespertina (Linnaeus, 1758) ●

Literature data with new records: 90, 91 (Vilenica et al. 2014)

New records: 134

71. Paraleptophlebia submarginata (Stephens, 1835)

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 79, 83, 84, 85, 86, 87, 88 (Vilenica et al. 2014)

New records: 8, 14, 26, 53, 60, 61, 74, 77, 98, 109, 110, 118, 119, 120, 128, 134, 137, 138, 139, 141, 142, 162

72. Paraleptophlebia werneri Ulmer, 1920 ●

Literature data with new records: 85, 90 (Vilenica et al. 2014)

IX. Oligoneuriidae Ulmer, 1914

73. Oligoneuriella rhenana (Imhoff, 1852)

Literature data: Bauernfeind and Soldán (2012)

New records: 26, 27, 32

X. Palingeniidae Albarda, 1888

74. Palingenia longicauda (Olivier, 1791)

Literature data: Bauernfeind and Soldán (2012)

XI. Polymitarcyidae Banks, 1900

75. Ephoron virgo (Olivier, 1791)

Literature data: Bauernfeind and Soldán (2012)

XII. Potamanthidae Albarda, 1888

76. Potamanthus luteus (Linnaeus, 1767)

Literature data: Bauernfeind and Soldán (2012)

New records: 7, 8, 9, 10, 18, 35, 36, 37, 40

XIII. Siphlonuridae Ulmer, 1920 (1888)

77. Siphlonurus armatus (Eaton, 1870)

Literature data: Bauernfeind and Soldán (2012)

78. Siphlonurus croaticus Ulmer, 1920

Literature data: Bauernfeind and Soldán (2012)

Literature data with new records: 82, 83, 85, 87 (Vilenica et al. 2014)

New records: 55, 66, 111, 123, 128, 130, 135■, 137

79. Siphlonurus lacustris (Eaton, 1870)

Literature data: Bauernfeind and Soldán (2012)

New records: 26, 27, 30, 73, 76

Community composition

The majority of the Croatian mayfly species were found to be associated with rivers and streams (Table 2). Among these, larvae of ten species also occurred within the spring areas (Table 2). Eleven species recorded in lakes and/or ponds were also found to inhabit flowing-water habitats. Cluster analysis (Fig. 2) showed that based on the mayfly assemblage, sampling sites were mainly structured first by ecoregion and then by habitat type. Species richness at the sampling sites and diversity indices are presented in Table 4. Species richness ranged from 2 and 18 species, Shannon-Weaver index between 0.21 and 1.96 and Simpson index between 0.11 and 0.82. All sampling sites with the highest species richness and diversity indices were situated in the Dinaric western Balkan ecoregion (ER5).

Figure 2.

Cluster analysis of mayfly community composition, based on Bray-Curtis Similarity (See Table 1 for codes).

Species richness (S), Shannon-Weaver (H’) and Simpson (1-λ) indices of diversity, calculated for 34 sites. Sites with the highest H’ and 1-λ are in bold.

Sampling site S H’ 1-λ
8 7 1.38 0.65
18 6 1.05 0.54
40 6 1.19 0.62
41 5 1.09 0.55
42 2 0.56 0.4
60 5 0.31 0.12
61 11 0.76 0.31
62 8 0.85 0.44
79 5 0.95 0.56
80 4 1.01 0.61
81 3 0.98 0.59
82 7 0.77 0.39
83 10 1.70 0.75
84 9 1.43 0.69
85 12 1.67 0.75
86 10 1.51 0.71
87 7 1.41 0.67
88 5 1.06 0.59
89 3 0.86 0.56
90 6 0.52 0.24
91 4 0.86 0.43
92 3 1.06 0.66
109 10 1.77 0.75
110 9 1.42 0.69
135 2 0.21 0.11
137 9 1.30 0.66
138 9 1.26 0.65
139 11 1.35 0.61
140 6 1.31 0.65
141 18 1.96 0.81
142 11 1.83 0.82
143 7 1.09 0.52
146 4 1.09 0.59
147 8 1.08 0.56

The SIMPER analysis between sites within the same habitat type showed an average similarity ranging from 35.1% for the Pannonian lowland rivers to 57.3% for the springs (Table 5).

SIMPER analysis for similarities in mayfly community composition in different habitat types (Pannonian lowland river, Dinaric river, Spring, Tufa barrier, Lake). Average similarity reflects the percentage between samples within one habitat type.

Habitat type Average similarity Taxa Av.Abund Av.Sim Sim/SD Contrib% Cum.%
Pannonian lowland river 35.10 C. macrura 3.56 10.09 1.12 28.76 28.76
H. sulphurea 2.64 9.02 0.95 25.69 54.45
P. luteus 2.72 7.64 0.98 21.77 76.22
P. bifidum 0.98 3.74 0.58 10.66 86.88
C. rivulorum 1.46 2.32 0.32 6.61 93.49
Dinaric river 37.92 S. ignita 4.64 11.97 1.47 31.57 31.57
B. rhodani 4.46 10.05 1.49 26.49 58.06
Rh. braaschi 3.16 5.18 0.73 13.67 71.73
P. submarginata 1.85 2.41 0.69 6.35 78.08
E. lineata 1.62 1.68 0.59 4.43 82.51
B. liebenauae 1.1 0.99 0.4 2.6 85.11
B. lutheri 1.45 0.89 0.27 2.36 87.47
C. luteolum 1.04 0.64 0.45 1.7 89.16
E. danica 0.94 0.6 0.31 1.58 90.74
Spring 57.32 Rh. braaschi 5.21 33.1 3.43 57.75 57.75
B. rhodani 4.44 20.02 3.11 34.93 92.67
Tufa barrier 53.92 E. danica 4.66 18.86 12.75 34.98 34.98
P. submarginata 2.99 11.45 9.54 21.24 56.21
C. luteolum 2.85 8.47 2.05 15.7 71.92
B. rhodani 2.31 6.07 0.58 11.26 83.18
B. cf. nubecularis 2.94 5.71 0.58 10.59 93.77
Lake 54.64 C. horaria 4.44 21.65 2.46 39.63 39.63
E. danica 2.42 16.91 2.67 30.96 70.59
C. luteolum 3.08 13.41 1.9 24.55 95.14

Discussion

Due to the paucity of systematic studies, mayfly fauna and their habitat preferences in Croatia were very poorly known, with records of only 50 species (Bauernfeind and Soldán 2012, Kovács and Murányi 2013, Ćuk et al. 2015). As expected, this study showed a higher diversity: 66 taxa were recorded, of which 29 for the first time in Croatia (Table 2). Combined with the literature, the species list consists of 79 taxa. Croatia is a relatively small Balkan country divided into two Ecoregions: Dinaric western Balkan (ER5) and Pannonian lowland (ER11) (Illies 1978) due to its position on the crossroads of Central and Mediterranean Europe, which is why its mayfly fauna shows transitive characteristics.

As a result, species with wide (e.g. Baetis rhodani, Cloeon dipterum, Caenis horaria, Serratella ignita), patchy (e.g. Procloeon nana, Leptophlebia vespertina, Caenis beskidensis) central European (e.g. Baetis cf. nubecularis, Ecdyonurus zelleri, Electrogena ujhelyii) as well as southern (e.g. Ephemera zettana) and Balkan (e. g. Electrogena mazedonica, Rhithrogena braaschi, Ephemera cf. parnassiana) distribution were recorded in Croatia. Additionally, 15 taxa were found that were not previously recorded in the Dinaric western Balkan ecoregion: Baetis cf. nubecularis, Procloeon nana, Caenis beskidensis, Ephemera cf. parnassiana, Ecdyonurus macani, E. submontanus, E. torrentis, Electrogena affinis, E. mazedonica, E. ujhelyii, Heptagenia longicauda, Rhithrogena braaschi, Habroleptiodes confusa, Leptophlebia vespertina and Paraleptophlebia werneri (Buffagni et al. 2007, 2009, Bauernfeind and Soldán 2012).

The new records include several morphologically interesting taxa: Rhithrogena from the diaphana group, Baetis cf. nubecularis and Ephemera cf. parnassiana. The Rhithrogena species from the diaphana group is morphologically similar to Rhithrogena savoiensis Alba-Tercedor & Sowa, 1987. However, DNA analysis based on mitochondrial COI gene shows it to be more closely related to Rhithrogena beskidensis Alba-Tercedor & Sowa, 1987 (Vuataz unpubl. results). Thus, reliable identification cannot be distinguished at this time. Comparison with other Balkan Rhithrogena diaphana group species and further detailed studied are required. A similar case is recorded for the Baetis alpinus group (sensu Müller-Liebenau, 1969), which presents the morphological characteristics that are intermediate between Baetis alpinus and B. nubecularis. Interestingly, the species is only recorded in high numbers (Vilenica et al. 2014) in the mountain Dinaric karst streams and tufa barriers in the area of Plitvice Lakes National Park (Table 1, Fig. 1). One male imago of the genus Ephemera Linnaeus, 1758, was caught in the Lopoško vrelo stream in southern Croatia. Its morphological features correspond to Ephemera parnassiana, a species that has currently only been recorded from Greece; however due to the small sample size, additional specimens are necessary for accurate identification of the species.

As most sites were in running waters and often with a stony substrate, the most diverse genera were Baetis and Ecdyonurus, which are known to be very common in running waters of the Northern Hemisphere (Bauernfeind and Soldán 2012). The most widely distributed species were two eurytopic and eurythermic species: Baetis rhodani and Serratella ignita. Further study is required at new sampling sites to determine the distribution of eleven species recorded only at only a single sampling site (Cloeon simile, Procloeon nana, Caenis pusilla, Ephemera cf. parnassiana, Leptophlebia vespertina, Ecdyonurus vitoshensis, E. zelleri, Electrogena mazedonica, Heptagenia coerulans, H. flava, H. longicauda, Rhithrogena iridina, Rh. gr. diaphana and Rh. semicolorata), as well as to determine the presence of the thirteen species listed in the literature which were not confirmed in this study (Ametropus fragilis, Ameletus inopinatus, Metreletus balcanicus, Siphlonurus armatus, Brachycercus harrisellus, Ephemera glaucops, Palingenia longicauda, Ephoron virgo, Choroterpes picteti, Ecdyonurus aurantiacus, E. siveci, Kageronia fuscogrisea and Rhithrogena germanica). The rare or unconfirmed presence of most of these species is likely due to the lack of seasonal sampling. It is possible that they were present at some sampling sites included in this study, but at a very young instar or even egg stage, and as such were overlooked. Additionally, some species might have become extinct from the Croatian rivers, such as Palingenia longicauda, which at present likely only inhabits the Danube River and Tisza River in Hungary, Slovakia and Ukraine (Bauernfeind and Soldán 2012).

The Black Sea basin includes 62% of Croatian rivers (Jelić et al. 2008), which likely explains the higher number of mayfly species recorded in this basin than in the Adriatic Sea basin.

The Dinaric region is considered to be a biodiversity hotspot (Bãnãrescu 2004, Griffiths et al. 2004, Ivković and Plant 2015). Despite a similar number of taxa recorded in each ecoregion, the highest species diversity was recorded for the fast flowing streams and rivers in the Dinaric western Balkan ecoregion. Similar results were obtained in the study of aquatic dance flies in Croatia (Ivković et al. 2013). The lowest number of mayfly species was found in springs and lakes (Table 4). Various studies have shown that mayfly species diversity is generally low in spring areas (Berner and Pescador 1988, Bauernfeind and Moog 2000, Maiolini et al. 2011). The only spring with four species was the spring of the Ruda River (146) in southern Croatia (Fig. 1), which is largely fed with water from the Buško Blato reservoir (Štambuk-Giljanović 2001, Bonacci and Roje-Bonacci 2003) that is relatively rich in nutrients and organic matter (Štambuk-Giljanović 2001). Thus, mayfly communities in the Ruda River spring are more species diverse and have a high proportion of detritivores (Vilenica unpubl. results). Most mayfly species prefer lotic habitats with a larger array of microhabitats, and these are less diverse in spring areas and lentic habitats. The present study confirmed the results of many previous studies (Berner and Pescador 1988, Elliott et al. 1988, Bauernfeind and Humpesch 2001, Bauernfeind and Soldán 2012).

Mayfly larvae inhabit flowing and standing freshwater ecosystems where they occupy a range of microhabitats in correlation with different biotic and abiotic factors. Additionally, in running water habitats, due to the longitudinal gradient of the physico-chemical characteristics of the water, different parts of the watercourse are inhabited by different mayfly species (Elliott et al. 1988, Bauernfeind and Humpesch 2001). Cluster analysis (Fig. 2) based on mayfly assemblage generally showed that sampling sites are structured first by ecoregion and then by habitat type. For this reason, due to their morphology and water properties (Lucić et al. 2015), the large, slow Pannonian lowland rivers (Sava, Drava, Kupa) are separated from the other sampling sites situated in the Dinaric western Balkan ecoregion. SIMPER analysis (Table 5) showed that the Pannonian mayfly community consisted of species that prefer epipotamalic sections of rivers, such as Caenis macrura, Procloeon bifidum, Heptagenia sulphurea and Potamanthus luteus (Buffagni et al. 2007, 2009, Bauernfeind and Soldán 2012). Due to the two common mayfly species present in high numbers, Baetis rhodani and Rhithrogena braaschi (Vilenica et al. 2014, Vilenica unpubl. results), the investigated springs clustered together with the small mountain karst rivers. Larger karst rivers clustered together due to the presence of species with a wide ecological range as Baetis rhodani, Centroptilum luteolum, Serratella ignita and Paraleptophlebia submarginata, and species with a southern European distribution such as Rhithrogena braaschi. Another common species was Baetis liebenauae, previously recorded in smaller streams with a sandy or stony bottom as well as in large lowland rivers, where it can be found as a habitat specialist on macrophytes (Buffagni et al. 2007, 2009, Bauernfeind and Soldán 2012). The presence of a stony bottom and submerged vegetation may be a suitable habitat combination for the species. Further research is required to determine the more specific preferences at the microhabitat scale and physico-chemical properties of the water. The mayfly species diversity is generally quite poor in lentic habitats, though certain taxa can be very abundant. The main reason why lakes clustered together and apart from other sites was due to their species composition consisting of taxa from lentic (e.g. Caenis horaria) or a wide range of habitat type preferences (e.g. Centroptilum luteolum, Ephemera danica; Bauernfeind and Soldán 2012). Due to the presence and abundance of the species Baetis rhodani, B. cf. nubecularis, Centroptilum luteolum, Serratella ignita, Ephemera danica and Paraleptophlebia submarginata, the lower streams in the Plitvice Lakes National Park (sites 84 and 85) grouped together with the tufa-barriers (see also in Vilenica et al. 2014).

In comparison with the neighbouring countries and with consideration of their surface areas, the Ephemeroptera diversity in Croatia could be characterised as relatively high. Together with Croatia, Bosnia and Herzegovina is also situated in Dinaric western Balkan ecoregion (ER5) (Illies 1978). However, as its mayfly fauna is currently poorly known, with only 52 species recorded, and as a large part of Croatian territory belongs to the Pannonian lowland ecoregion, to which most of the Hungarian territory also belongs, the Croatian mayfly fauna was found to be most similar to the Hungarian fauna (75%, Table 3). This is due to the presence of widely distributed species and of the species inhabiting the larger rivers. Even though the mayfly fauna of Bosnia and Herzegovina is currently poorly known, 65% of the species were similar to the Croatian fauna. Thus, it is possible that a much greater similarity between these countries can be expected in the future. Italy is divided into two completely different ecoregions than Croatia: Italy (ER3) and Alps (ER4) (Illies 1978). It had a much higher mayfly diversity and the lowest similarity with the Croatian mayfly assemblage (55%, Table 3). This is possibly due to its geographical position and large surface area that includes a great variety of geographical features and diverse habitats. For example, the Alps, which are not present in Croatia, are well-known for their mayfly diversity and endemism, especially in the genus Rhithrogena Eaton, 1881 (Vuataz et al. 2011).

Conclusions

As expected, this study revealed a higher number of mayfly taxa inhabiting Croatian freshwater habitats than known from the previous literature. As two of the most similar mayfly assemblages of the neighbouring countries have several taxa that could also inhabit Croatian habitats (e. g. Baetis vardarensis Ikonomov, 1962, Rhithrogena picteti Sowa, 1971, Leptophlebia marginata (Linnaeus, 1767), Ephemerella notata Eaton, 1887, Caenis luctuosa (Burmeister, 1839)) but were not yet recorded, due to the lack of systematic sampling in all seasons, future studies should include seasonal sampling of a higher number of sites and habitat types. Additionally, the main focus should be on the eastern lowland part of the country, where a lower number of sites was visited during this study.

In the present study, some interesting taxa with restricted European and local distributions were recorded (e.g. Rhithrogena gr. diaphana, Baetis cf. nubecularis and Ephemera cf. parnassiana). Considering these species were recorded from a small number of sites in this study, they could be considered rare. Future studies on the taxonomic status, ecological features and detailed distribution of these species is necessary.

Additionally, as Baetis liebenauae was recorded on larger karstic rivers, a different habitat type than previously known, more detailed information on its preferences at the microhabitat scale and water physico-chemical properties should be investigated.

Acknowledgements

This study was conducted as a part of the following projects: “Arthropod biological diversity in protected karstic habitats in Croatia” (No. 119-1193080-1206) led by Prof. Dr. Mladen Kučinić and “Invertebrate taxonomy, ecology and biogeography of Croatian aquatic ecotones” (No. 119-1193080-3076) led by Prof. Dr. Mladen Kerovec. We would like to thank them for their support. We would also like to thank all our colleagues who greatly helped with field sampling and with the isolation of numerous macrozoobentos samples. Many thanks to: Anita Belančić, Matija Bučar, Klaas-Douwe B. Dijkstra, Marija Ivković, Miljenko Ivković, Mirjana Jelenčić, Andreja Komljenović, Martina Krbavčić, Ivančica Krulik, Petar Kružić, Jasna Lajtner, Andreja Lucić, Vlatka Mičetić-Stanković, Milorad Mrakovčić, Martina Pavlak, Bruna Polak, Aleksandar Popijač, Ana Previšić, Igor Stanković, Sanja Sviben, Matija Šimac, Ivan Vučković, Sanja Žalac, Krešimir Žganec. Many thanks to the curator of the Slovene Natural History Museum, Tomi Trilar, for his facility and hospitality. Many thanks to Igor Stanković and Miran Katar for help with artwork, and to Laurent Vuataz and Ana Previšić for help with DNA sequencing.

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