Representation of the Hyrcanian forest (northern Iran) in modern pollen rain revealed by palynological and DNA-metabarcoding data

Abstract

We studied the modern pollen rain in two different landscapes from Hyrcanian lowland forests up to the slopes of the Alborz Mountains in Gilan province for the first time. Pollen traps were installed for one year and moss samples were collected along two altitudinal transects from 100 to 1800 m and from 100 to 2300 m elevations. The results of pollen counting and environmental DNA barcoding (metabarcoding) of the collected pollen and moss samples were compared from 32 locations. In total, 81 vascular plant species from 36 families were identified by metabarcoding, and 68 taxa belonging to 39 families were identified by pollen counting. The pollen counting results reflect mainly wind-pollinated families, such as Betulaceae and Fagaceae while results from metabarcoding of the rbcL and ITS2 loci were more in line with the vegetation around the pollen traps and the moss samples. Furthermore, this study showed that the rbcL region is able to identify more taxa than the ITS2 region, while applying both markers provides higher confidence. Also using both metabarcoding and pollen data provides a better local and regional vegetation representation.