Vladimir Stevanović’s research while affiliated with Serbian Academy of Sciences and Arts and other places

The Balkan Peninsula is considered one of the most important centres of orchid diversity in Europe. However, the patterns of orchid species richness in the Central Balkans have not been sufficiently studied so far. The aim of this study was, therefore, to identify the centres of orchid diversity and the factors that influence the spatial variation in orchid species richness in the Central Balkans. For the analyses, the area of the Central Balkans was divided into 10 × 10 km grid cells. The environmental variables determined for each grid cell and used in the analyses were altitude, bioclimatic variables, geological substrates and habitat types. A random forest (RF) analysis was used to identify the environmental predictors most strongly associated with species richness. In addition to the total number of taxa, orchids with three belowground organ types were analysed separately: (a) rhizomatous orchids, (b) orchids with palmately lobed and fusiform tubers ("palmate tuberous orchids") and (c) orchids with spherical or ovoid tubers ("ovoid tuberous orchids"). In the Central Balkans, 54 orchid species and subspecies have been recorded, and the most important centres of diversity are the Tara, Zvijezda, Jadovnik and Zlatar Mountains and the Ovčar-Kablar Gorge. In general, two groups of grid cells with the largest number of orchid taxa, i.e., hotspots, stood out: (1) grid cells with a large altitudinal range and (2) grid cells occupied by gorges and ravines. The most important gradients influencing orchid species richness are specific habitat types and altitudinal ranges, while climatic factors and geological substrates are less important. The most important factors affecting the richness of total and rhizomatous orchids are altitudinal range and habitat types (Abieti-Fagenion, Ostryo-Carpinion orientalis and Pinion nigrae forests), highlighting the important role of habitat heterogeneity. The maximum altitude, percentage of Abieti-Fagenion and Vaccinio-Picetea forests and the minimum value of the mean temperature of the driest quarter are the most important factors for determining the richness of palmate tuberous orchids, whereas the percentage of xero-thermophilous habitat types (Ostryo-Carpinion orientalis, Asplenietea trichomanis and Pinion nigrae) has the greatest influence on the richness of ovoid tuberous orchids. These results confirm the hypothesis concerning the origin and development of underground organs in orchids, emphasising that palmate tuberous orchids are best adapted to cold and humid habitat conditions, whereas ovoid tuberous orchids have the ability to grow in habitats with very warm and dry conditions. This study provides a good basis for better orchid conservation planning and underlines the importance of belowground strategies as a feature of orchid life history that should be considered when studying patterns of orchid diversity.

Ferns are a plant group that has been neglected in terms of research on their distribution, ecology and conservation in Serbia. This study reports the first findings of Athyrium distentifolium (Athyriaceae) in Serbia and presents the distribution of three other ferns of the Serbian flora (Thelypteris limbosperma, Thelypteris palustris and Phegopteris connectilis) from the family Thelypteridaceae. The distribution data were obtained on the basis of field investigations, checking and revision of herbarium material and published sources. The distribution maps of these taxa in Serbia were created on a 10×10 km UTM grid system. Data on their habitat and ecological preferences, conservation status and threat factors within the study area are provided.

In this paper we suggest three new nomenclatural combinations and specify two new synonyms. There are five taxa (species and subspecies) of the vascular plants that are new for the flora of Serbia, and four species that have been confirmed for the flora of our country. Five plant taxa are a novelty for proper Serbia, Vojvodina, or Kosovo and Metohija, of which four are autochthonous and one is an allochthonous and invasive plant. There are twelve taxa whose presence in Serbia or in its territorial units has been refuted. the name Viola ×foliosa Čelak., which was proposed in the previous issue of this scientific journal, has been corrected to the currently accepted V. ×kerneri Wiesb.

This paper represents the fourth part of the inventory of the flora of Serbia (Niketić et al. 2018, 2020, 2021), which contains nomenclatural, taxonomic and floristic notes related to taxa from the Magnoliopsida group. At the same time, this contribution is the basis for publication of subsequent volumes of the An annotated checklist of vascular flora of Serbia in order to supplement the data on vascular plants in our country.

Understanding patterns of species diversity along an altitudinal gradient is the major topic of much biogeographical and ecological research. The aim of this study was to explore how richness and density of orchid species and subspecies in terms of different categories of underground organ systems and pollination systems vary along an altitudinal gradient in the central Balkans. The altitudinal gradient of the study area was divided into 21 100-m vertical intervals. Data were analyzed using both non-linear and linear regressions with three data sets (total orchids, orchids of forest habitats, orchids of non-forest habitats) in the case of species richness and three data sets (total orchids—total area, forest orchids—forest area, and orchids of non-forest habitats—non-forest area) in the case of species density. The results showed a hump-shaped pattern of orchid richness and density, peaking at 900–1,000 m. The richness and density of orchids of forest habitats are generally slightly greater than the richness and density of orchids of non-forest habitats in lowland areas, whereas the orchids of herbaceous vegetation types dominating at high altitudes. Tuberous orchids dominate in low and mid-altitude areas, orchids with palmately lobed and fusiform tubers (“intermediate orchids”) dominate at high altitudes, while rhizomatous orchids are predominate in mid-altitude forest stands. Both deceptive and self-pollinated orchids show a unimodal trend with a peak at mid-altitude areas. This study underlines the importance of low and mid-altitude areas for the survival of deceptive orchids and the importance of mid- and high-altitude areas for the survival of rewarding orchids. In addition, forest habitats at mid-altitudes have been shown to be crucial for the survival of self-pollinated orchids. The results suggest that the altitudinal patterns of orchid richness and density in the central Balkans are determined by mechanisms related to land area size and habitat cover, partially confirming the species-area relationship (SAR) hypothesis. This study contributes significantly to a better understanding of the potential impacts of habitat changes on orchid diversity, thereby facilitating more effective conservation planning.

The genus Ramonda includes three Paleoendemic and Tertiary relict species that survived in refugial habitats of the Balkan Peninsula (R. nathaliae and R. serbica) and the Iberian Peninsula (R. myconi). They are all “resurrection plants,” a rare phenomenon among flowering plants in Europe. Ramonda myconi and R. nathaliae are diploids (2n = 2x = 48), while R. serbica is a hexaploid (2n = 6x = 144). The two Balkan species occur in sympatry in only two localities in eastern Serbia, where tetraploid potential hybrids (2n = 4x = 96) were found. This observation raised questions about the existence of gene flow between the two species and, more generally, about the evolutionary processes shaping their genetic diversity. To address this question, genetic markers (AFLP) and an estimate of genome size variation were used in a much larger sample and at a larger geographic scale than previously. The combination of AFLP markers and genome size results suggested ongoing processes of interspecific and interploidy hybridization in the two sites of sympatry. The data also showed that interspecific gene flow was strictly confined to sympatry. Elsewhere, both Ramonda species were characterized by low genetic diversity within populations and high population differentiation. This is consistent with the fact that the two species are highly fragmented into small and isolated populations, likely a consequence of their postglacial history. Within sympatry, enormous variability in cytotypes was observed, exceeding most reported cases of mixed ploidy in complex plant species (from 2x to >8x). The AFLP profiles of non-canonical ploidy levels indicated a diversity of origin pathways and that backcrosses probably occur between tetraploid interspecific hybrids and parental species. The question arises whether this diversity of cytotypes corresponds to a transient situation. If not, the question arises as to the genetic and ecological mechanisms that allow this diversity to be maintained over time.

The paper proposes eight new nomenclatural combinations and indicates two new synonyms. There are 11 taxa (species and subspecies) of the vascular flora that are new for the flora of Serbia (of which nine are autochthonous and two allochthonous plants). Two autochthonous species were confirmed for the flora of Serbia. Six plant taxa are a novelty for proper Serbia, Vojvodina, or Kosovo and Metohija. There are eight taxa whose presence in Serbia or in its territorial units has been refuted.

The Balkan Peninsula is one of the most important centers of orchid diversity in Europe. However, the orchid flora in the central Balkans and southern part of the Pannonian Plain is still not sufficiently known. Therefore, this chapter reviews the orchid flora of Serbia, considering its taxonomic structure, life forms, and pollination systems. Moreover, detailed insight into the chorological groups of individual taxa is provided. Long-term personal field investigations, checking and revision of herbarium material, and relevant published sources were used to complete the overview of orchid taxa present in Serbia. In total, 72 orchid species and subspecies belonging to 22 genera have been recorded in Serbia, whereas the presence of three taxa is doubtful. Taxonomic analysis shows that the most species-rich genera are Epipactis and Dactylorhiza (10 taxa each), followed by Anacamptis (nine taxa), then Orchis (eight taxa) and Ophrys (seven taxa). Examination of the life form spectrum indicates that orchids with ovoid tubers are the most numerous, followed by rhizomatous orchids, whereas there are slightly fewer taxa belonging to the group of orchids with palmately lobed and fusiform tubers. As far as pollination systems are concerned, the deceptive system is present in the greatest number of orchids, the rewarding system is the second largest system, whereas self-pollinating orchids are less numerous. Phytogeographical analysis shows domination of Central European and Mediterranean-Submediterranean taxa, followed by taxa from the Eurasian and boreal chorological groups. The importance of the Balkan endemics Himantoglossum calcaratum subsp. calcaratum and Dactylorhiza cordigera subsp. bosniaca and that of three subendemics of the Carpathians and the Balkans (Gymnadenia frivaldii, Dactylorhiza maculata subsp. transsilvanica, and Dactylorhiza cordigera subsp. cordigera) are especially emphasized. In addition, this synthesis underlines the fact that the study area provides suitable conditions for the survival of some orchid species that have southern or northern limits of their distribution in this part of southeastern Europe. Bearing in mind the great diversity of relief, vegetation, climatic conditions, geological substrates, and soil characteristics, as well as the action of historical factors, we assume that the number of orchid species in Serbia could be higher and expect that new taxa will eventually be recorded. The chapter highlights the importance of the role played by orchid life history strategies in studies of diversity patterns, as well as the need for detailed future research on the taxonomy, chorology, ecology, and conservation of orchids in Serbia.

Terrestrial orchids in Europe inhabit a variety of vegetation types, both the forest and scrub types and herbaceous vegetation. The richness and composition of orchid species and subspecies in relation to vegetation types in the central Balkans (western Serbia) were investigated in the present study. In total, the phytocoenological affiliation of 55 orchid species and subspecies were analysed. Based on presence/absence data, similarity of the orchid flora among different vegetation types (orders and alliances) was analysed using the clustering method. Orchids were recorded in plant communities from 17 classes, 31 orders and 41 alliances. The greatest number of orchid species grow in communities of the classes Festuco-Brometea, Molinio-Arrhenatheretea and Quercetea pubescentis, the orders Quercetalia pubescenti-petraeae, Brachypodietalia pinnati, Fagetalia sylvaticae as well as the alliances Fagion sylvaticae, Fraxino orni-Ostryion, Nardo-Agrostion tenuis and Arrhenatherion elatioris. The results show that the vegetation types richest in orchid taxa are those that occur over a wide range of altitudes, mainly on carbonate substrates and on various bedrock types, indicating the cumulative effect of environmental factors in determining the patterns of orchid species richness. Furthermore, Gymnadenia conopsea, Anacamptis morio, Dactylorhiza saccifera, Platanthera bifolia, Neottia ovata and Dactylorhiza sambucina were found to grow in the largest number of vegetation types, suggesting their great ecological plasticity. In total, 12 statistically significant groups of vegetation orders and 11 statistically significant groups of vegetation alliances are distinguished. The study highlights the importance of certain vegetation types in defining priorities of orchid conservation.

In the original publication of the article, there were two minor errors identified. They are as follows: