Orchid diversity along an altitudinal gradient in the central Balkans

Abstract

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.

Biogeography of orchids and their pollination syndromes in small Mediterranean islands

“…Although their small seeds make them good dispersers, these islands may not provide the environmental conditions required for these species to stabilize permanently. Our findings are consistent with previous research indicating that elevation is a recognized predictor of orchid richness (Ackerman et al., 2007; Djordjević et al., 2022). This relation is particularly strong for both autogamous and rewarding groups indicating an altitudinal gradient on Mediterranean islands as well as supporting what has been found in both insular and continental contests (Djordjević et al., 2022; Jacquemyn et al., 2005).…”

“…Our findings are consistent with previous research indicating that elevation is a recognized predictor of orchid richness (Ackerman et al., 2007; Djordjević et al., 2022). This relation is particularly strong for both autogamous and rewarding groups indicating an altitudinal gradient on Mediterranean islands as well as supporting what has been found in both insular and continental contests (Djordjević et al., 2022; Jacquemyn et al., 2005). This pattern can be explained by the fact that these syndromes are very often associated with meadows and forests dominated by Quercus ilex which occur on the most elevated islands very often as remnant of an intense human impact at lower elevations.…”

“…Few studies deal with the geographic distribution of reproductive strategies. Both in tropical and temperate biomes, a greater diversity of species was found at intermediate altitudes, but deception is more often found on low mid‐altitudes, rewarding strategies on mid‐high altitudes and self‐pollinated on high elevation (Djordjević et al., 2022; Jacquemyn et al., 2005; Pellissier et al., 2010; Štípková et al., 2020). The area–species relationship in orchids has been positively tested (Ackerman et al., 2007; Schödelbauerová et al., 2009; Taylor et al., 2021) although attention to the Mediterranean region has only recently been addressed (Lussu et al., 2020; Tsiftsis, 2020).…”

Orchid Diversity at Three Elevations in the Mountain Sandstone Plateaus of the Cordillera del CóndorEcuador

“…Orchids (epiphytes and terrestrial) are important components of tropical forests [29,30] and have important roles in the total biomass, water balance, and nutrient cycling of ecosystems [30,31]. Due to their ecological significance, orchids have been used for several years as indicators of environmental changes related to land use [32,33], forest disturbance [23,34], or the effects of environmental factors, such as elevation [35][36][37][38]. In this context, the main findings suggest a bell-shaped distribution of species richness with elevation [30,[34][35][36][37][38].…”

“…Due to their ecological significance, orchids have been used for several years as indicators of environmental changes related to land use [32,33], forest disturbance [23,34], or the effects of environmental factors, such as elevation [35][36][37][38]. In this context, the main findings suggest a bell-shaped distribution of species richness with elevation [30,[34][35][36][37][38]. Following this pattern for Ecuador, Küper et al [39] showed a bell-shaped elevational pattern of orchid richness.…”