Pollen morphology of Norwegian hybrids of Sorbus L.
Abstract
The genus Sorbus consists of small to medium-sized trees primarily found
in coastal areas, with three European hotspots for diversification:
Fennoscandia, South-East Europe, and Britain. Taxonomic classification
of Sorbus in Europe is still unresolved, and this study aims to address
this issue by examining the pollen morphology of different Sorbus
hybrids. Pollen morphology of 16 specimens from 13 species of Sorbus,
Aria and Hedlundia, some of which are common, while others are endemic
and listed as threatened species, were studied. Measurements of the
polar and equatorial axis of all pollen show that there are variations
in pollen size and shape among different hybrids, with correlation
between polyploidy levels and the width of the pollen. Surface
structures of 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 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.