DOI: 10.5061/dryad.hmgqnk9p3
title: Measures of equatorial and polar lengths of pollen grains in Sorbus, Aria and Hedlundia from Norway

description: The genus Sorbus s.l. consists of small to medium-sized trees primarily
 found in coastal areas, with three European hotspots of diversification:
 Fennoscandia, South-East Europe, and the British Isles. Taxonomic
 classification of Sorbus s.l. in Europe is still unresolved, and this
 study aims to address this issue by examining the pollen morphology of
 various Sorbus hybrids. Pollen morphology of 16 specimens from 13 species
 of Sorbus s.str., Aria and Hedlundia, some of them common, others are
 endemic and listed as threatened species, were studied. Measurements of
 the polar and equatorial axis of all pollen grains show that there are
 variations in pollen size and shape among different hybrids, with a
 correlation between ploidy levels and the equatorial diameter of the
 pollen. Surface structures of the pollen were observed using SEM.
 Principal Component Analysis (PCA) was performed to analyze the pollen
 characters, and the results show that it is possible to separate Aria from
 Sorbus and Hedlundia based on the length of the polar axis of the pollen
 grain, while the number of perforations is important for classification
 within Hedlundia. The study concludes that pollen morphology can be a
 useful tool for distinguishing between different Sorbus hybrids and can
 thus aid in understanding their past distributions.
description: Specimens were collected from various parts of Norway in 2019,
 either from native stands or from cultivated plants of known origin
 (Figure 1, Table1). Inflorescences were collected and dried of samples of
 Aria edulis (Wild.) M.J. Roemer, Aria obtusifolia (DC.) Sennikov &
 Kurtto, Aria rupicola (T.C.G. Rich) Sennikov & Kurtto, Hedlundia
 hybrida 1 (L.) Sennikov & Kurtto, Hedlundia hybrida 2 (L.)
 Sennikov & Kurtto, Hedlundia lancifolia (Hedl.) Sennikov &
 Kurtto, Hedlundia meinichii 1 (Lindeb. ex Hartman) Sennikov &
 Kurtto, Hedlundia meinichii 2 (Lindeb. ex Hartman) Sennikov &
 Kurtto, Hedlundia mougeotii (Soyer-Willemet & Godron) Sennikov
 & Kurtto, Hedlundia neglecta (Hedl.) Sennikov & Kurtto,
 Hedlundia sognensis (Hedl. ex Sennikov, Hjertson & Salvesen)
 Sennikov & Kurtto, Hedlundia subarranensis (Hyl. ex Sennikov,
 Hjertson & Salvesen) Sennikov & Kurtto, Hedlundia
 subpinnata 1 (Hedl.) Sennikov & Kurtto, Hedlundia subpinnata 2
 (Hedl.) Sennikov & Kurtto, Hedlundia subsimilis (Hedl.) Sennikov
 & Kurtto, and Sorbus aucuparia L. Anthers were
 treated with 10% KOH to remove cell contents, followed by acetolysis to
 remove cellulose (Fægri et al., 1989). The pollen was stained using
 fuchsine and mounted in glycerol. Using a light microscope (LM) the polar
 axis (P) and equatorial axis (E) of 100 pollen grains of each specimen
 were measured.
description: # Pollen grain measures of Sorbus, Aria and Hedlundia
 The dataset contain
 measures of the polar axis (P) and equatorial axis (E) of 100 pollen
 grains of each specimen. Anthers were treated with 10% KOH to remove cell
 contents, followed by acetolysis to remove cellulose (Fægri et al., 1989).
 The pollen was stained using fuchsine and mounted in glycerol. Using a
 light microscope (LM) the polar axis (P) and equatorial axis (E) of 100
 pollen grains of each specimen were measured. Measurements of the polar
 and equatorial axis of all pollen grains show that there are variations in
 pollen size and shape among different hybrids of Sorbus, with a
 correlation between ploidy levels and the equatorial diameter of the
 pollen. Taxonomic classification of Sorbus s.l. in Europe is still
 unresolved, and this study aims to address this issue by examining the
 pollen morphology of various *Sorbus* hybrids. Pollen morphology of 16
 specimens from 13 species of *Sorbus* s.str., *Aria* and *Hedlundia*, some
 of them common, others are endemic and listed as threatened species, were
 studied. The study concludes that pollen morphology can be a useful tool
 for distinguishing between different Sorbus hybrids. ## Description of the
 data and file structure The data is given in a excel sheet. All data are
 given in um.