Abstract
Understanding the abundance and distribution patterns of species at large spatial scales is one of the goals of biogeography and macroecology, as it helps researchers and authorities in designing conservation measures for endangered species. Orchids, one of the most endangered groups of plants, have a complicated system of pollination mechanisms. Their survival strongly depends on pollination success, which then determines their presence and distribution in space. Here we concentrate on how pollination mechanisms (presence/absence of nectar) are associated with orchid species density and mean niche breadth along an altitudinal gradient in six different phytogeographical regions in the Czech Republic. We found differences between these regions in terms of orchid species numbers and density. The trend (hump-shaped curve) in species density of nectarless and nectariferous orchids were very similar in all phytogeographical regions, peaking between 300–900 m. The trend strongly depends on habitat cover and pollinator availability. In general, the most specialist species of orchids were found from low to middle altitudes. The association of altitude with the richness of orchid flora is much stronger than that with the biogeography. Climate change is a factor that should not be neglected, as it may affect the presence/absence of many species in the future.
Highlights
Orchids are disappearing worldwide[1], mostly due to habitat loss, but other factors are expected to increase in importance during the 21st century[2,3]
A step was taken in this direction by Tsiftsis et al.[9], who explored the associations between orchid species density, mean niche breadth and mean distribution on the one hand and selected predictors on the other hand, using regression techniques for all orchids, and for those with different root systems
Tsiftsis et al.[9] show that species density for the three below ground strategies is significantly associated with the predictors, whereas their mean niche breadth and mean distribution largely are associated with their evolutionary history represented by the corresponding root system
Summary
Orchids are disappearing worldwide[1], mostly due to habitat loss, but other factors (e.g. climate change and resulting shifts in species distributions) are expected to increase in importance during the 21st century[2,3]. Tsiftsis et al.[9] show that species density for the three below ground strategies is significantly associated with the predictors, whereas their mean niche breadth and mean distribution largely are associated with their evolutionary history represented by the corresponding root system. Most plants that are pollinated by animals produce and offer rewards to attract pollinators to visit their flowers (nectariferous species[14]). Some plants attract pollinators they do not offer them any reward in their flowers (nectarless species[17,18]). Nectariferous orchids are better competitors for pollinators than nectarless orchids[30] All this has consequences for fruit production and fitness of the plants. Nectariferous species have a higher fruit set than nectarless ones[26,29,31,33] in all geographical areas[29] due to pollination limitation[26,29]
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