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The Q1 spread of alien crustaceans has significantly contributed to the homogenization of macroinvertebrate fauna of European freshwaters. However, little is known about alien Peracarida crustaceans of the Sava River, which represents the most important corridor for the spread of invasive species into Dinaric rivers with highly endemic fauna. In this study, we investigated Peracarida (Amphipoda, Isopoda and Mysida) collected during three years (2011, 2012 and 2015) from a total of 61 sites along the entire course of the Sava River. Besides describing the longitudinal pattern of Peracarida assemblages, we tested the hypothesis that bank reinforcement structures facilitate peracarid invasions by comparing densities and assemblages on natural and artificial substrate at 15 sites. In a total, 14 peracarid crustacean species (5 native and 9 alien) were recorded. The Upper third of Sava was inhabited by native peracarids only, while the Middle and Lower Sava were dominated by alien species. The invasive amphipods Dikerogammarus haemobaphes, Chelicorophium sowinskyi and Chelicorophium curvispinum, and invasive isopod, Jaera istri, were the most abundant species along the middle course. Densities of alien peracarids in the Middle Sava were the highest and their share in macroinvertebrate assemblages was very variable, while the Lower Sava had the highest number of alien species in low densities. The densities of alien amphipods and isopods were in most cases significantly higher on bank reinforcement structures than on natural substrate. Therefore, artificial stony substrates act as stepping stones of invasion for alien peracarids and largely contribute to their success in large lowland rivers.

Slatkovodne školjke iz familije Unionidae, predstavljaju jednu od najznačajnijih i široko rasprostranjenih komponenata vodenih ekosistema kopnenih voda. Ekološka uloga ove taksonomske grupe u vodenim ekosistemima je od velikog značaja, s obzirom da predstavlja bitan element strukture i funkcije bentosnih zajednica. Raznovrsnost i rasprostranjenje unionida, do sada, nije adekvatno proučeno u Srbiji, kako u pogledu broja vrsta, tako i u odnosu na opšte poznavanje rasprostranjenja pojedinih vrsta i faktora koji utiču na pojavu taksona i gustinu populacija. Ciljevi ovog istraživanja bili su: pregled ukupnog broja vrsta u Srbiji; analiza strukture i dinamike populacija unionida; definisanje odnosa vrsta i najznačajnijih parametara okruženja; analiza morfološke varijabilnosti različitih populacija, primenom metoda geometrijske i tradicionalne morfometrije i kao krajnji cilj, procena rizika od izumiranja akvatičnih vrsta na nacionalnom nivou i predlog strategije konzervacije. Materijal korišćen za analizu prikupljen je pri realizacije više nacionalnih i međunarodnih projekata u periodu 2001.-2013. godina. Osim savremenih istraživanja, analizom su obuhvaćeni i istorijski podaci, dobijene na osnovu pregleda dostupne zbirke Ante Tadića, Prirodnjačkog muzeja u Beogradu, iz perioda 1953.-1972. Sveobuhvatnom analizom materijala, na prostoru Srbije je utvrđeno prisustvo 7 vrsta slatkovodnih školjki iz familije Unionidae, svrstanih u četiri roda. Najveći diverzitet i brojnost populacije zabeleženi su u donjim tokovima velikih ravničarskih reka (zoni potamona). U radu je dat detaljan pregled sastava zajednica istraživanih slivova, sa prikazom taksonomskih i ekoloških karakteristika pojedinačnih vrsta. Poredeći istorijske podatke o nalazima vrsta i savremena istraživanja, uočene su promene u veličini areala i populacionoj dinamici pojedinih taksona. Značajno smanjenje areala, odnosno potpuno povlačenje sa prostora gde je nekada nalažena, utvrđeno je za vrstu A. cygnea, a kao njeni refugijumi mogu se označiti lentički ekosistemi kakve su akumulacije, jezera i barsko močvarna područja u Srbiji. Na osnovu istorijskih podataka utvrđeno je da je vrsta U. crassus nekada bila široko rasprostranjena i jedna od najprisutnijih vrsta na celom području Srbije do sredine 70-ih godina prošlog veka. Nakon tog perioda, istraživanjima izvršenim u poslednjih nekoliko dekada, uočen je pad brojnosti populacije ove vrste i samo sporadični nalazi na ograničenom prostoru. Najnovija istraživanja ukazuju na pozitivan populacioni trend ove vrste, pri čemu se naročito izdvaja sliv Save. Ispitivanje odnosa prisutnih vrsta prema fizičko-hemijskim karakteristikama vode na analiziranim lokalitetima, pokazalo je da su najvažniji fizičko-hemijski parametri: koncentracija kalcijuma, ukupna tvrdoća vode, BPK, HPK, koncentracija nitrata i amonijum jona. Rezultati kanonijske korespondentne analize ukazuju na očekivano veću osetljivost vrste U. crassus na BPK5, HPK, koncentraciju nitrata i amonijum jona, odnosno veću toleranciju vrste A. anatina na pomenute faktore. Kao najznačajniji parametri uticaja na zajednicu slatkovodnih školjki, iz grupe teških metala, izdvajaju se koncentracije bakra, olova i kadmijuma u vodi. Rezultati kanonijske korespondentne analize ukazuju na povećanu osetljivost vrste U. crassus na ove faktore, dok je veća tolerancija utvrđena za A. anatina. Primenom metoda geometrijske morfometrije, analizirana je varijabilnost veličine i oblika levog kapka ljušture različitih populacija savremenih uzoraka školjki i analiza jedinki koje su pripadale muzejskim uzorcima. Geometrijsko morfometrijskom analizom recentnih uzoraka potvrđeno je postojanje statistički značajnih međupopulacionih razlika u varijabilnosti veličine i oblika morfoloških struktura. Analizom varijavilnosti morfoloških struktura uzoraka iz muzejske zbirke, primenom metoda geometrijske morfometrije, nije potvrđeno postojanje značajnih razlika u varijabilnosti veličine i oblika različitih podvrsta, izuzev u slučaju U. tumidus. Analizom varijabilnosti ljuštura na osnovu devet dužinskih karaktera, primenom tradicionalnog morfometrijskog pristupa, utvrđeno je postojanje međupopulacionih razlika i sličan trend odstupanja kao i pri geometrijsko morfometrijskoj analizi. Primenom modifikovanog modela ESHIPPO-PD, utvrđen je rizik od izumiranja i prioritet konzervacije na lokalnom nivou za analizirane vrste. Za U. crassus, P. complanata i A. cygnea određen je prvi stepen prioriteta zaštite, odnosno visok nivo rizika od izumiranja na nacionalnom nivou. Umereni rizika od izumiranja (II stepen prioriteta konzervacije) ocenjen je za vrste U. pictorum i A. anatina, dok se za U. tumidus uočava da je rizik od izumiranja manji (III stepen prioriteta zaštite). Analizom elemenata modela (ES+HIPPO+PD), izdvajaju se faktori koji najviše utiču na ugroženost datih vrsta i na taj način omogućavaju definisanje adekvatnih mere konzervacije na nacionalnom nivou. Freshwater mussels from the family Unionidae, represent one of the most significant and widespread components of inland water ecosystems. Ecological role of this taxonomic group within water ecosystems is of great significance being an important structural and functional element of benthic communities. The diversity and distribution of Unionidae have not been researched adequately so far in Serbia, neither the species richness, nor general distribution of individual species and factors affecting the emergence of the taxon and populations density. The aims of this research were: review of total number of species in Serbia; analysis of structure and dynamics of Unionidae populations; definition of relations between species and most significant environment parameters; morphological variability analysis of different populations applying the method of geometric and traditional morphometrics and, as the final aim, risk evalulation regarding aquatic species extinction on national level and a conservation strategy recommendation. Material used for analysis was collected during the realization of several national and international projects during the period 2001-2013. Besides contemporary researches, the analysis also includes historical data obtained from available collection of Ante Tadić from the Natural History Museum in Belgrade, period 1953-1972. A thorough material analysis in the region of Serbia led to the determination of presence of 7 fresh water mussels species from family Unionidae, classified into 3 genera. The highest diversity and population abundance were recorded in lower parts large lowland rivers (potamon zone). The detailed overview of communities composition found in the investigated river basins with a review of taxonomic and ecological traits of individual species was presented. The comparison of historical data and contemporary investigations shows there are changes in habitat size and population dynamics of individual taxons. Significant reduction in the habitat size, i.e. complete retreat from the area where it used to be found earlier was determined for the species A. cygnea and lentic ecosystems can be marked as their refugium, such as accumulations, lakes, marsh and swamp regions in Serbia. Based on historical data, it was determined that U. crassus species used to be widespread and one of the most represented species in whole region of Serbia until mid-1970's. After that period, in the investigations carried out during last several decades, the decrease in the number of this population was observed, as well as only sporadic findings in a limited area. The latest investigations indicate to a positive population trend of this species, especially in the Sava river basin. The invastigation of relations among present species based on physical and chemical characteristics of water in analyzed localities has shown that the most important physical and chemical parameters are as follows: Calcium concentration, total water hardness, BPK5, HPK, nitrate concentration and ammonium ion concentration. The results of canonical correspondence analysis indicate to an expectedly higher sensitivity of species U. crassus to BPK, HPK, nitrates and ammonium ion concentration, i.e. greater tolerance of species A. anatina to the above listed factors. The parameters with the most significant influence on freshwater mussels community among the group of heavy metals are the concentrations of copper, lead and cadmium in water. The results of canonical correspondence analysis indicate to an increased sensitivity of species U. crassus to these factors, while a greater tolerance of species A. anatina to these factors was recorded. Using geometric morphometrics method, the size and shape variability of shell left valva of different contemporary shell populations samples were analized, as well as the specimens belonging to museum samples. Geometric morphometrics analysis of recent samples confirms the existence of statistically significant ntrapopulation differences in size and shape variability of morphological structures. Morphological structures variability analysis of museum samples, applying the geometric morphometrics method, does not confirm the existence of significant differences within variability of size and shape of various varieties, except in the case of U. tumidus. Using shell variability analysis based on nine linear characters, applying the traditional morphometric approach, the existence of intrapopulation differences was determined, as well as a similar trend of deviations like in geometric morphometrics analysis. Applying the modified model ESHIPPO-PD, the risk of extinction and the priority of conservation on a local level were determined for the analized species. The first level of protection priority was determined for U. crassus, P. comlanata and A. cygnea, i.e. high extinction risk at local level. A moderate risk (the second level of conservation priority) was estimated for species U. pictorum and A. anatina, while the extiction risk is lower for U. tumidus (the third level of protection priority). The analysis of element included in model ES+HIPPO+PD, singles out the factor of greatest influence on endangeredness of given species.

The Asian clam, Corbicula fluminea (Müller, 1774) is a native species of fresh and brackish water in Southeast Asia. The species was introduced in North America in the early 20th century and from there it was brought to Europe, first in Portugal and France, by ballast water in the 1980s. The successful invasion of this species can be explained by specific life history strategy: good dispersion abilities, high fecundity and growth rates, high ecological tolerance, short lifespan, and some particular reproductive features, as well as by human assistance. The species competes with native bivalves, reducing their abundance and population density, and may be responsible for the extinction of some species. The first record of C. fluminea in Croatia dated from 2001 when the species was recorded in the Danube River. In the meantime, C. fluminea was found in the downstream part of the Sava and Drava Rivers. Our research confirmed upstream spreading of the species in both rivers and their tributaries (e.g. rivers Kupa and Una). Density was the highest in coarse sand and sand with gravel (e.g. 4400 ind./m2 in the Sava River at site Krapje, which accounted for 96 % of the total number of bivalves). We assume that C. fluminea in the inland waters of Croatia spreads by natural mechanisms (passive upstream and downstream movement), which are probably facilitated by some human activities, such as boating, fishing, fish stocking and aquaculture, recreational activities, and sand and gravel extraction.

Slatkovodne školjke iz familije Unionidae, predstavljaju jednu od najznačajnijih i široko rasprostranjenih komponenata vodenih ekosistema kopnenih voda. Ekološka uloga ove taksonomske grupe u vodenim ekosistemima je od velikog značaja, s obzirom da predstavlja bitan element strukture i funkcije bentosnih zajednica. Raznovrsnost i rasprostranjenje unionida, do sada, nije adekvatno proučeno u Srbiji, kako u pogledu broja vrsta, tako i u odnosu na opšte poznavanje rasprostranjenja pojedinih vrsta i faktora koji utiču na pojavu taksona i gustinu populacija. Ciljevi ovog istraživanja bili su: pregled ukupnog broja vrsta u Srbiji; analiza strukture i dinamike populacija unionida; definisanje odnosa vrsta i najznačajnijih parametara okruženja; analiza morfološke varijabilnosti različitih populacija, primenom metoda geometrijske i tradicionalne morfometrije i kao krajnji cilj, procena rizika od izumiranja akvatičnih vrsta na nacionalnom nivou i predlog strategije konzervacije. Materijal korišćen za analizu prikupljen je pri realizacije više nacionalnih i međunarodnih projekata u periodu 2001.-2013. godina. Osim savremenih istraživanja, analizom su obuhvaćeni i istorijski podaci, dobijene na osnovu pregleda dostupne zbirke Ante Tadića, Prirodnjačkog muzeja u Beogradu, iz perioda 1953.-1972. Sveobuhvatnom analizom materijala, na prostoru Srbije je utvrđeno prisustvo 7 vrsta slatkovodnih školjki iz familije Unionidae, svrstanih u četiri roda. Najveći diverzitet i brojnost populacije zabeleženi su u donjim tokovima velikih ravničarskih reka (zoni potamona). U radu je dat detaljan pregled sastava zajednica istraživanih slivova, sa prikazom taksonomskih i ekoloških karakteristika pojedinačnih vrsta. Poredeći istorijske podatke o nalazima vrsta i savremena istraživanja, uočene su promene u veličini areala i populacionoj dinamici pojedinih taksona. Značajno smanjenje areala, odnosno potpuno povlačenje sa prostora gde je nekada nalažena, utvrđeno je za vrstu A. cygnea, a kao njeni refugijumi mogu se označiti lentički ekosistemi kakve su akumulacije, jezera i barsko močvarna područja u Srbiji. Na osnovu istorijskih podataka utvrđeno je da je vrsta U. crassus nekada bila široko rasprostranjena i jedna od najprisutnijih vrsta na celom području Srbije do sredine 70-ih godina prošlog veka. Nakon tog perioda, istraživanjima izvršenim u poslednjih nekoliko dekada, uočen je pad brojnosti populacije ove vrste i samo sporadični nalazi na ograničenom prostoru. Najnovija istraživanja ukazuju na pozitivan populacioni trend ove vrste, pri čemu se naročito izdvaja sliv Save. Ispitivanje odnosa prisutnih vrsta prema fizičko-hemijskim karakteristikama vode na analiziranim lokalitetima, pokazalo je da su najvažniji fizičko-hemijski parametri: koncentracija kalcijuma, ukupna tvrdoća vode, BPK, HPK, koncentracija nitrata i amonijum jona. Rezultati kanonijske korespondentne analize ukazuju na očekivano veću osetljivost vrste U. crassus na BPK5, HPK, koncentraciju nitrata i amonijum jona, odnosno veću toleranciju vrste A. anatina na pomenute faktore. Kao najznačajniji parametri uticaja na zajednicu slatkovodnih školjki, iz grupe teških metala, izdvajaju se koncentracije bakra, olova i kadmijuma u vodi. Rezultati kanonijske korespondentne analize ukazuju na povećanu osetljivost vrste U. crassus na ove faktore, dok je veća tolerancija utvrđena za A. anatina. Primenom metoda geometrijske morfometrije, analizirana je varijabilnost veličine i oblika levog kapka ljušture različitih populacija savremenih uzoraka školjki i analiza jedinki koje su pripadale muzejskim uzorcima. Geometrijsko morfometrijskom analizom recentnih uzoraka potvrđeno je postojanje statistički značajnih međupopulacionih razlika u varijabilnosti veličine i oblika morfoloških struktura. Analizom varijavilnosti morfoloških struktura uzoraka iz muzejske zbirke, primenom metoda geometrijske morfometrije, nije potvrđeno postojanje značajnih razlika u varijabilnosti veličine i oblika različitih podvrsta, izuzev u slučaju U. tumidus. Analizom varijabilnosti ljuštura na osnovu devet dužinskih karaktera, primenom tradicionalnog morfometrijskog pristupa, utvrđeno je postojanje međupopulacionih razlika i sličan trend odstupanja kao i pri geometrijsko morfometrijskoj analizi. Primenom modifikovanog modela ESHIPPO-PD, utvrđen je rizik od izumiranja i prioritet konzervacije na lokalnom nivou za analizirane vrste. Za U. crassus, P. complanata i A. cygnea određen je prvi stepen prioriteta zaštite, odnosno visok nivo rizika od izumiranja na nacionalnom nivou. Umereni rizika od izumiranja (II stepen prioriteta konzervacije) ocenjen je za vrste U. pictorum i A. anatina, dok se za U. tumidus uočava da je rizik od izumiranja manji (III stepen prioriteta zaštite). Analizom elemenata modela (ES+HIPPO+PD), izdvajaju se faktori koji najviše utiču na ugroženost datih vrsta i na taj način omogućavaju definisanje adekvatnih mere konzervacije na nacionalnom nivou. Freshwater mussels from the family Unionidae, represent one of the most significant and widespread components of inland water ecosystems. Ecological role of this taxonomic group within water ecosystems is of great significance being an important structural and functional element of benthic communities. The diversity and distribution of Unionidae have not been researched adequately so far in Serbia, neither the species richness, nor general distribution of individual species and factors affecting the emergence of the taxon and populations density. The aims of this research were: review of total number of species in Serbia; analysis of structure and dynamics of Unionidae populations; definition of relations between species and most significant environment parameters; morphological variability analysis of different populations applying the method of geometric and traditional morphometrics and, as the final aim, risk evalulation regarding aquatic species extinction on national level and a conservation strategy recommendation. Material used for analysis was collected during the realization of several national and international projects during the period 2001-2013. Besides contemporary researches, the analysis also includes historical data obtained from available collection of Ante Tadić from the Natural History Museum in Belgrade, period 1953-1972. A thorough material analysis in the region of Serbia led to the determination of presence of 7 fresh water mussels species from family Unionidae, classified into 3 genera. The highest diversity and population abundance were recorded in lower parts large lowland rivers (potamon zone). The detailed overview of communities composition found in the investigated river basins with a review of taxonomic and ecological traits of individual species was presented. The comparison of historical data and contemporary investigations shows there are changes in habitat size and population dynamics of individual taxons. Significant reduction in the habitat size, i.e. complete retreat from the area where it used to be found earlier was determined for the species A. cygnea and lentic ecosystems can be marked as their refugium, such as accumulations, lakes, marsh and swamp regions in Serbia. Based on historical data, it was determined that U. crassus species used to be widespread and one of the most represented species in whole region of Serbia until mid-1970's. After that period, in the investigations carried out during last several decades, the decrease in the number of this population was observed, as well as only sporadic findings in a limited area. The latest investigations indicate to a positive population trend of this species, especially in the Sava river basin. The invastigation of relations among present species based on physical and chemical characteristics of water in analyzed localities has shown that the most important physical and chemical parameters are as follows: Calcium concentration, total water hardness, BPK5, HPK, nitrate concentration and ammonium ion concentration. The results of canonical correspondence analysis indicate to an expectedly higher sensitivity of species U. crassus to BPK, HPK, nitrates and ammonium ion concentration, i.e. greater tolerance of species A. anatina to the above listed factors. The parameters with the most significant influence on freshwater mussels community among the group of heavy metals are the concentrations of copper, lead and cadmium in water. The results of canonical correspondence analysis indicate to an increased sensitivity of species U. crassus to these factors, while a greater tolerance of species A. anatina to these factors was recorded. Using geometric morphometrics method, the size and shape variability of shell left valva of different contemporary shell populations samples were analized, as well as the specimens belonging to museum samples. Geometric morphometrics analysis of recent samples confirms the existence of statistically significant ntrapopulation differences in size and shape variability of morphological structures. Morphological structures variability analysis of museum samples, applying the geometric morphometrics method, does not confirm the existence of significant differences within variability of size and shape of various varieties, except in the case of U. tumidus. Using shell variability analysis based on nine linear characters, applying the traditional morphometric approach, the existence of intrapopulation differences was determined, as well as a similar trend of deviations like in geometric morphometrics analysis. Applying the modified model ESHIPPO-PD, the risk of extinction and the priority of conservation on a local level were determined for the analized species. The first level of protection priority was determined for U. crassus, P. comlanata and A. cygnea, i.e. high extinction risk at local level. A moderate risk (the second level of conservation priority) was estimated for species U. pictorum and A. anatina, while the extiction risk is lower for U. tumidus (the third level of protection priority). The analysis of element included in model ES+HIPPO+PD, singles out the factor of greatest influence on endangeredness of given species.

Lowland rivers are exposed to severe anthropogenic degradation, which leads to the alteration of natural substrates. Such degradation in river morphology can significantly influence the community structure of aquatic macroinvertebrates by increasing the quantity of manmade substrates (e.g. riprap). Due to the preferences of specific taxa, a survey of the community found on artificial substrates can significantly bias the result of a community structure analysis, characteristic for a particular habitat. Chironomidae larvae are the dominant group among aquatic macroinvertebrates, and yet their sensitivity to substrate composition changes has only been considered in a few studies. In this work, we wanted to test whether the community structure in the Sava River (Balkan Peninsula) differed significantly on natural and artificial substrate. Also, the intention was to detect which taxa group contributed to the changes in the community structure. The distribution and separation of the sampling sites on a Non Metric Dimensional Scaling (NMDS) plot were mostly influenced by the substrate type. NMDS analysis presented two groups of sites assigned with specific community structure. The indicator value analysis (IndVal) revealed important chironomid representatives for both groups of sites (natural and artificial substrates). The significance of substrate specificity, as an important factor influencing the chironomid community structure, was confirmed by a distance-based permutational multivariate analysis of variance (PERMANOVA), as well as IndVal, since different indicator taxa inhabited different microhabitats in the same sampling sites. This information stresses the importance of the substrate type, pointing out that in determining the representative community for a certain habitat, artificial substrates should be avoided in sampling design. This is especially true for bioassessment and river typology methods where the community structure is used as a multivariate indicator.

The objective of this study is to present the comparable data on macroinvertebrate communities from the natural bottom substrate along the middle and lower stretch of the Sava River. The study was carried out in September 2011 at eight sites of the sector between Zagreb - Martinska Ves and Belgrade – at the confluence into the Danube. The data presented could be used as baseline information for any future management of the main course of the Sava River.

Research on the community of aquatic macroinvertebrates was carried out during 2005 and 2006 at four sampling sites along the Jablanica River, a right-hand tributary of the Kolubara River. Fifty-seven taxa were recorded in the course of the investigation. The most diverse group was Ephemeroptera, followed by Trichoptera and Plecoptera. Members of the Rhitrogena semicolorata group were the most abundant. Our results could be the basis for evaluation of the influence of damming of the Jablanica River on the status of its water and can serve as a model for studying the influ­ence of hydromorphological degradation of aquatic ecosystems. Istraživanja zajednice akvatičnih makrobeskičmenjaka vršena su tokom 2005. i 2006. godine na četiri lokaliteta reke Jablanice, desnog sastavka Kolubare. Ukupno je zabeleženo 57 taksona. Najraznovrsnije grupe su bile Ephemeroptera, Trichoptera i Plecoptera. Najbrojniji takson je Rhitrogena semicolorata Gr. Dobijeni rezultati predstavljaju osnovu za procenu uticaja izgradnje brane na status vode reke Jablanice i mogu biti korišćeni kao model za ispitivanje uticaja hidromorfoloških promena na vodene ekosisteme uopšte. Projekat ministarstva br. 143023