The Effect of Population Density on Morpho-Ecological Characteristics of the Rare Species Pontechium maculatum (Boraginaceae) in “Iron Gates” Natural Park (Romania)

Pontechium maculatum (Boraginaceae) is a species of high conservation concern in the Romanian flora. It is assigned the national IUCN category “vulnerable”, legally protected according to the national Biological Diversity Act, and listed in Annex II of the Habitats Directive (Council Directive 92/43/EEC). P. maculatum, formerly known as Echium russicum, is a biennial herbaceous plant, rare in many parts of its range and even critically endangered in some countries. In Romania, populations of this species are found in several areas of Transylvania, Moldova, Dobrogea, and Oltenia, mostly within protected areas, with the number of individuals reaching over 1500, and the populations being stable with a favorable conservation status. In the present study, ten populations of P. maculatum from the “Iron Gates” Natural Park in SW Romania were analyzed. For each density, the composition of the plant community was assessed, as well as some morphological and physiological parameters of the plants. The results indicated the phytocoenotic variability of the species, with a different dominant abundance in the floristic composition of several plant communities. Statistical analysis of quantitative traits revealed variability depending on density (at lower densities, plants have a higher number of leaves and photosynthetic rate). Also, the photosynthetic rate was mainly temperature-dependent, rising with this factor. This research found that in some areas, there are insufficient numbers of individuals due to invasive species. The identified variability of Pontechium maculatum in the “Iron Gates” Natural Park is demonstrated by the interplay of ecological factors, human influence, and conservation efforts. Our findings suggest that effective conservation strategies should focus on managing invasive species and enhancing habitat conditions to support P. maculatum populations.