No abstract

Vegetative dormancy, that is the temporary absence of aboveground growth for ≥ 1 year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life-history costs of sprouting, and of dormancy. Short-lived and mycoheterotrophic species have higher proportions of dormant plants than long-lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.

Despite their low frequency, minority cytotypes substantially increase intraspecific and intrapopulation ploidy diversity estimates for fragrant orchids. The cytogenetic structure of Gymnadenia populations is remarkably dynamic and shaped by multiple evolutionary mechanisms, including both the ongoing production of unreduced gametes and heteroploid hybridization. Overall, it is likely that the level of ploidy heterogeneity experienced by most plant species/populations is currently underestimated; intensive sampling is necessary to obtain a holistic picture.

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.