Diversity and distribution of stoneflies in the area of Plitvice Lakes National Park and along the Mediterranean river Cetina (Croatia)

Abstract

The stonefly fauna of Croatia is poorly known with only 28 species so far officially recorded. This number should be much higher because for some neighbouring countries about 100 stonefly species are known. The aim of this work was to investigate and to compare the diversity and distribution of stoneflies in the continental and the Mediterranean part of the Western Dinaric region in Croatia. The results are based on identification of adult insects and larvae. Adult Plecoptera were collected at the Plitvice Lakes National Park during two years using pyramid-type emergence traps and window traps with 28 stonefly species collected. The research of stonefly fauna of Cetina River was conducted during a one-year period and adults of 15 stonefly species were found. Among 37 stonefly species recorded for both study areas only six species are shared, and 19 species are new for the Croatian fauna as important new findings for the Croatian part of Dinaric region.

Keywords:

• Plecoptera
• diversity
• Western Dinarids
• Croatia
• Plitvice Lakes
• Cetina River

Introduction

The distribution and the zoogeography of European stoneflies are better known than for most insects (Zwick 1980). This is not true, however, of all parts of former Yugoslavia. For Slovenia (Sivec 2001), Bosnia and Herzegovina (Kaćanski 1976), and Macedonia (Ikonomov 1986) they are relatively well known, whereas only fragmentary data are available from other regions of former Yugoslavia and almost none from Croatia (Sivec 1980, 1985).

Due to lack of material, it is virtually impossible to evaluate several old records (Klapálek 1899, 1906a, 1906b; Pongrácz 1913, 1914). We have therefore ignored them together with recent data of ecological and limnological studies based only on unreliable determination of larval stages (Matoničkin 1959a, 1959b, 1987; Matoničkin and Pavletić 1959, 1961, 1965, 1967a, 1967b; Matoničkin et al. 1969, 1971; Pavletić and Matoničkin 1972; Habdija and Primc 1987; Habdija 1988; Habdija et al. 1994, 1997, 2000a, 2000b, 2002, 2004; Žganec 2005).

Therefore the stonefly fauna of Croatia is poorly known with only 28 species so far officially recorded (Sivec 1980, 1985), based on reliable determination of adult insects and eggs. Most likely, this number represents just a small part of the species present in Croatia, because about 100 stonefly species are known for the neighbouring Slovenia (Sivec 2001), making Slovenia one of the areas with the richest and most diverse stonefly fauna in Europe. Because Croatia borders several limno-geographical regions (Illies 1978), many additional stonefly species for Croatia should be found, including perhaps endemic species and some species new to science.

The aim of this work was to study and to compare the diversity and distribution of stoneflies in the continental and the Mediterranean part of the Western Dinaric region in Croatia. In addition, our goal was to find additional records of stonefly species for the poorly known stonefly fauna of Croatia.

Study area

One part of this study was carried out in the Plitvice Lakes National Park, located in the mountainous NW region of Croatia, in the Lika region, and presenting a part of Danube River drainage network. For details on the study area in the Plitvice Lakes National Park, see Previšić et al. (2007).

The second part of this study was carried out along the Mediterranean river Cetina, in the Dalmatinska Zagora region, southern Croatia. The Cetina River is the longest Mediterranean drainage area river in Croatia (about 105 km) that never dries out and belongs to the permanent hydrological systems. For details on the study area in the Cetina River system, see Ivković et al. (2007).

All sampling sites are located on permanent hydrological systems. Figures 1 –3 and Tables 1–2 show the sampling sites at both study areas.

Figure 1. Terrain and watercourses map of Croatia with study areas.

Figures 2–3. Maps of the study areas with sampling sites in the (2) Plitvice Lakes National Park and (3) Cetina River system.

Figure 4. Cluster analysis of similarity between sampling sites based on composition of adult stonefly fauna.

Table 2. Sampling sites in the Cetina River system.

Abbr.	Locations	Elevation (m)	Distance from source (km)
SS	Cemetery (Sveti Spas) spring	385	0
CS	Cetina spring	386	0
PS	Preočani spring	378	0
PB	Preočani bridge	373	1.5
RB	Red bridge	369	2.5
OS	Obrovac Sinjski	300	39
T1	Trilj 1	297	55
T2	Trilj 2	296	56
ČL	Čikotina lađa	253	65
RM	Radmanove mlinice	5	99
RS	Ruda spring	341	0
R2	Ruda 2	315	0.15
GS	Grab spring	332	0

Materials and methods

The results are based mostly on identification of adult insects and only in some cases are larvae taken into consideration.

Adult Plecoptera were observed at five sampling sites in the Plitvice Lakes National Park (Table 1, Figure 2) during two years (2000 and 2001) using pyramid-type emergence traps and window traps (Previšić et al. 2007). Qualitative samples of the adult Plecoptera were collected manually at these locations occasionally from 2002 until recently.

The study of stonefly larvae of Cetina River was conducted from August 2004 until August 2005. Quantitative samples of larvae were collected with Surber net and D-net at 11 different locations through the whole flow of the Cetina River and spring area of its main tributary, the Ruda River (Table 2, Figure 3). Qualitative samples of the adult Plecoptera and larvae were collected manually and with entomological nets at locations at the same time and occasionally until recently, and at additional springs of two tributaries, spring Sveti Spas and the spring of the stream Grab (tributary of Ruda River).

Table 1. Sampling sites in the Plitvice Lakes National Park.

Abbr.	Locations	Elevation (m)	Distance from source (km)
BR	Spring of Bijela rijeka (White River spring)	738	0
CR	Spring of Crna rijeka (Black River spring)	706	0
PLJ	Crna rijeka (Black River), middle reach	680	1
LA	Labudovac travertine barrier	630	5.9
KM	Kozjak-Milanovac travertine barrier	546	9.6

All samples were fixed in 80% ethyl alcohol. In the laboratory they were analysed under a stereomicroscope and stored in 80% ethyl alcohol. Stonefly species or genera were identified using available literature of the nearest regions of Europe (Illies 1955; Aubert 1959, 1963; Kaćanski and Zwick 1970; Sowa 1970; Tabacaru 1971; Kis 1974; Hynes 1977; Raušer 1980; Ravizza 2002; Ravizza and Vinçon 1998; Sivec and Stark 2002; Graf and Schmidt-Kloiber 2003; Zwick 2004).

Cluster analysis using presence/absence data with the Bray–Curtis similarity measure (for binary data it is equal to the Sorenson similarity index) and the group average clustering method were used to determine the faunistic similarity of Plecoptera between studied sites. The analysis was performed with PRIMER Version 5.2.9 for Windows (Clarke and Warwick 2001).

Results

A total of 1551 individuals (506 males and 1045 females) of 25 species in 155 emergence trap samples were collected in the area of Plitvice Lakes National Park. Furthermore, together with occasional manual sampling, a total of 28 species of adult Plecoptera were recorded (16 new species for Croatia). Ten different genera from four families were recorded, four of which belong to the family Nemouridae (Amphinemura, Nemoura, Nemurella, Protonemura), three to the family Perlodidae (Besdolus, Isoperla, Perlodes), two to the family Taeniopterygidae (Brachyptera, Taeniopteryx), and one to the family Leuctridae (Leuctra). The location with the highest diversity in the area of Plitvice Lakes National Park was the middle reach of Crna rijeka (Black River) with 18 stonefly species recorded (Table 3).

Table 3. Distribution of recorded stonefly species across sampling sites in the Plitvice Lakes National Park and in the Cetina River system (19 species new for stonefly fauna of Croatia are highlighted in bold).

		PLITVICE					CETINA
	Species	BR	CR	PLJ	LA	KM	RS	R2	GS	SS	CS	PS	PB	RB	OS	T1	T2	ČL	RM
1.	Siphonoperla sp. (female)						x
2.	Leuctra albida	x		x	x	x
3.	Leuctra cingulata			x
4.	Leuctra fusca			x	x	x									x			x	x
5.	Leuctra handlirschi		x	x
6.	Leuctra hippopus			x
7.	Leuctra inermis		x	x
8.	Leuctra major				x
9.	Leuctra mortoni										x	x	x	x
10.	Leuctra nigra	x	x	x	x	x
11.	Leuctra prima	x	x	x
	Leuctra sp. (larvae)							x			(x)	(x)	(x)	(x)	(x)			(x)	(x)
12.	Amphinemura triangularis	x			x	x	x	x	x
13.	Nemoura avicularis				x	x
14.	Nemoura cinerea	x		x	x	x		x		x	x	x	x	x
15.	Nemoura flexuosa				x	x
16.	Nemoura marginata gr.			x	x	x
17.	Nemoura minima	x	x	x
18.	Nemurella pictetii	x		x	x
19.	Protonemura auberti	x	x	x
20.	Protonemura autumnalis										x
21.	Protonemura cf. hrabei									x	x	x
22.	Protonemura intricata	x			x	x
23.	Protonemura nitida		x	x	x	x
24.	Protonemura praecox			x	x	x
	Protonemura sp. (larvae)										(x)								x
25.	Dinocras megacephala						x	x
26.	Perla pallida						x	x	x	x		x		x				x	x
27.	Besdolus imhoffi				x	x												x	x
28.	Isoperla illyrica						x	x	x		x	x	x	x	x
29.	Isoperla inermis	x	x	x			x	x	x	x	x	x	x	x	x		x
30.	Isoperla cf. lugens	x	x
31.	Isoperla oxylepis					x
32.	Isoperla rivulorum	x
33.	Isoperla tripartita									x	x	x		x
34.	Isoperla sp. (female)														x
	Isoperla sp. (larvae)																(x)	x	x
35.	Perlodes cf. intricatus	x	x	x
36.	Brachyptera tristis	x	x				x	x	x	x	x	x	x	x	x	x
37.	Taeniopteryx cf. hubaulti	x	x	x
	Number of species:	15	12	18	14	13	7	8	5	6	8	8	5	7	5	1	1	4	5

A total of 4654 larvae of 12 taxa were collected in 154 benthos samples (from a total of 366 samples taken) along the Cetina River. Manual sampling of adults included 15 stonefly species collected (five new species for Croatia). Ten different genera from six families were recorded, three of which belong to the family Nemouridae (Amphinemura, Nemoura, Protonemura), two to the family Perlidae (Perla, Dinocras), two to the family Perlodidae (Besdolus, Isoperla), one to the family Leuctridae (Leuctra), one to the family Chloroperlidae (Siphonoperla), and one to the family Taeniopterygidae (Brachyptera). Locations with the highest diversity in the Cetina River system (eight species recorded) were the main Cetina spring, small lateral Cetina spring at Preočani village (about 1.5 km downstream) and Ruda 2 station, about 150 m downstream the Ruda spring (Table 3).

For both studied areas a total of 37 species of Plecoptera were collected and 19 species are new for Croatian fauna (Table 3).

Among 37 stonefly species recorded, only six species are shared between the two investigated areas: Isoperla inermis Kaćanski and Zwick, 1970; Brachyptera tristis (Klapálek, 1901); Amphinemura triangularis (Ris, 1902); Nemoura cinerea (Retzius, 1783); Besdolus imhoffi (Pictet, 1841) and Leuctra fusca (Linnaeus, 1758) (Table 3).

These results give a similarity index of only 14% between Plitvice Lakes National Park and the Cetina River system. Cluster analysis results grouped the stonefly fauna into these two groups, representing the different study areas. Inside each study area, grouping of sampling sites from upper, middle and lower reaches of the catchment area can be noticed (Figure 4).

Discussion

The stonefly fauna of Croatia is poorly known with only 28 species so far officially recorded (Sivec 1980, 1985). With this research, the number of confirmed stonefly species for Croatia increased, but also some puzzling stonefly specimens appeared. Some specimens were found that could not be absolutely certainly identified to known species. Problematic cases are listed below:

Perlodes cf. intricatus from Plitvice – most probably a new species, very similar to individuals collected by Dávid Murányi in Albania (W. Graf, pers. comm., July 9, 2007).

Perla pallida Type 3 (Greece) eggs, but adults resemble a sister species, P. marginata, and larvae are intermediate between these two species.

Isoperla inermis – is it really a species or only a Balkan form of I. difformis? Some morphological differences between individuals from Plitvice and Cetina are noted; specifically, males and females from Plitvice are almost double the size of males and females from Cetina River.

Isoperla cf. lugens from Plitvice – is it really a light coloured and bigger form of the alpine species, I. lugens, which normally lives above 1000 m a.s.l. or is it a new species?

Protonemura cf. hrabei from Cetina River – is it really P. hrabei or a new species? Females from Cetina emerge from the beginning of summer and they have some morphological differences with individuals from Central Europe, which emerge during autumn.

Protonemura autumnalis from Cetina River – only one male was collected during autumn 2005, and a few females, with many females of sister species Protonemura cf. hrabei, were collected by the beginning of summer 2007.

Protonemura auberti from Plitvice – some males and females are very similar to the sister species P. aestiva – suggesting a mix (hybrids) of these two species.

Nemoura marginata group from Plitvice – is it N. marginata or some other species from N. marginata group, which are in need of revision?

Leuctra inermis group from Plitvice – some adults look more like L. handlirschi, and some more like L. inermis.

Siphonoperla sp. from Ruda spring – only one female was collected by Wolfram Graf on joint fieldwork by the beginning of summer 2007. Males still have not been found.

Taeniopteryx cf. hubaulti from Plitvice – some characteristics of adults are similar to adults of T. auberti, suggesting an intermediate, possibly new species.

A cluster analysis of similarity between sampling sites based on composition of stonefly fauna resulted with a similarity index of only 14% between Plitvice Lakes National Park and Cetina River system (Figure 4), because among 37 stonefly species recorded for both study areas only six species are shared. Furthermore, in the Plitvice Lakes National Park much more species of smaller and colder streams like species of Leuctra and Nemoura are present (Table 3).

The most probable reasons for marked differences in stonefly fauna between the two investigated areas are:

different climate – cold and humid mountainous continental climate (Plitvice) versus warm and dry submediterranean to mediterranean climate (Cetina),

different catchment characteristics – mostly forest shaded heterogeneous streams and small springs (Plitvice) versus open sunny main river and quite big spring areas (Cetina),

different longitudinal gradient – higher elevations from 738 m to 546 m a. s. l. (Plitvice) versus lower elevations from 386 m to 5 m a. s. l. (Cetina), and

different degree of human impact – lowly inhabited and highly protected area of largest and oldest National Park in Croatia (from 1949, and on UNESCO list from 1979) versus highly inhabited area on almost all reaches of Cetina River, with unsolved reception of wastewater and high flow regulations (springs used for water supply, three reservoirs with dams, five hydroelectric power plants).

As a result of this research an increase of 68% in number of confirmed stonefly species for Croatia was noted (from 28 to 47 species). From 37 stonefly species recorded during this study, 19 species are new for the Croatian fauna and represent important new findings for the Croatian part of the Western Dinaric region (Table 3).

Conclusions

Results of this research confirm the assumption that the stonefly fauna of Croatia is poorly known and more focused stonefly studies on the territory of Croatia will surely result in many more confirmed stonefly species and most probably in the description of some new species for science. Our most recent studies on stoneflies in different parts of Croatia tend to confirm these assumptions (Popijač and Sivec 2006a, 2006b; Popijač 2007).

Acknowledgements

We wish to express our gratitude to Prof. Dr Mladen Kučinić, Ana Previšić, Ivan Vučković, Ivona Zrinski, Ivana Božak, Mirjana Jelenčić, Romana Gračan, Marija Ivković, Igor Stanković, Krešimir Žganec, Martina Kiš, Nives Herceg, Tihana Petrić, Dr Bogdan Horvat, Matjaž Černila, and Dr Wolfram Graf for help in collecting and processing the samples. For financial support, we would like to thank Prof. Dr Mladen Kerovec as well as the institution Hrvatske vode (Croatian Waters). For permission to sample in the highly protected area, we thank the Plitvice Lakes National Park authorities. We would like to thank Prof. Dr Bill P. Stark for his corrections of the English language and help with the text. For their warm hospitality during our Cetina research, we would like to thank the family Majstrović from Donji Bitelić. This research was supported by Croatian Ministry of Science, Education and Sports as a part of the Project No. 119-1193080-3076: Invertebrate taxonomy, ecology and biogeography of Croatian aquatic ecotones.