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Distribution and abundance of endemic species Degenia velebitica (Degen) Hayek (Brassicaceae)

The area of occupancy and estimation number of individuals of threatened and narrow endemic species Degenia velebitica (Degen) Hayek (Velebit, Croatia) were measured. The area of occupancy was defined on all known localities by defining the edges of areal by using GPS devices and elaboration by GIS tools. Abundance (density) was estimated according to the full counting of individual plants on 38 standard plots each with surface of 25 m2, and with approximation to the total area of occupancy. The results show that D. velebitica is present on total area of 4.8 ha with the estimated 37 000 individuals. Locality on Velika Kapela with two sub-localities occupy the largest area (44 600 m2) and have the highest estimated number of individuals (24 175), but with the lowest abundance (0.53/m2). Small and spatially close localities on South Velebit occupy area of 2790 m2, they are second according to the estimated number of plants (6 897), but with higher abundance ( <4.36/m2). Locality on Central Velebit is the smallest in area, but with utmost density (5.33/m2). On the locus classicus, Plana, the species was not found. A trend to gorse with natural potential vegetation was detected on all localities. Results should serve as a background for tracking population trends and for conservation action plans developing.

Degenia velebitica; distribution; endemic plant; threatened species; abundance; conservation

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