Abstract
The genus Rubus L. (Rosaceae) not been investigated satisfactorily in terms of palynology. This genus is taxonomically very difficult due to the large number of species and problems with their delimitation, as well as very different distribution areas of particular species. The aim of this study was to investigate pollen morphology and for the first time the ranges of intrageneric and interspecific variability of Rubus species, as well as verify the taxonomic usefulness of these traits in distinguishing studied taxa from this genus. The selected species of the genus Rubus were analysed for 11 quantitative pollen characteristics and the following qualitative ones: exine ornamentation, pollen outline and shape, as well as bridge structure. Analyses were conducted on a total of 1740 pollen grains, which represent 58 blackberry species belonging to a majority of subgenera and all the sections and series found in Poland. The most important characters included exine ornamentation (exine ornamentation type, width and direction of grooves and striae, number and diameter of perforations) and length of the polar axis (P). The arrangement of the examined species on the dendrogram does not corroborate division of the genus Rubus into subgenera, sections and series currently adopted in taxonomy. This fact is not surprising because the taxonomy of the genus was not based on pollen characters. Pollen features should be treated in taxonomy as auxiliary, because they fail to differentiate several (10) individual species, while the other ones create groups with similar pollen traits.
Highlights
Rubus L. is a large and diverse genus in the Rosaceae family with a worldwide distribution, including hundreds or even thousand of published species names and infrageneric taxa [1, 2]
The study was conducted on 58 Polish and European Rubus species, which represent four out of five subgenera, all three sections and all 23 series of blackberries found in Poland, including all six Polish endemic species (R. capitulatus, R. chaerophylloides, R. ostroviensis, R. posnaniensis, R. seebergensis and R. spribillei)
To a majority of palynologists, the authors of this study maintain that exine ornamentation features were diagnostic, that means they allow for differentiate species within the genus Rubus [24, 25, 27,28,29,30,31, 33, 34, 38, 39, 42, 46, 59]
Summary
Rubus L. is a large and diverse genus in the Rosaceae family with a worldwide distribution, including hundreds or even thousand of published species names and infrageneric taxa [1, 2]. The genus Rubus L. belongs to the tribe Rubeae Dumort., subfamily Rosoideae, family Rosaceae Juss. The genus Rubus was traditionally divided into 12 subgenera [13, 14]. The current classification recognises 13 subgenera, with the largest subgenus Rubus in turn divided into 12 sections [10]. This classification is clearly arbitrary, as many of the subgenera have been shown to be poly- or paraphyletic [15]. Other subgenera were distinguished from it: Chamaerubus, Cylactis, Anoplobatus and Idaeobatus, which were represented by individual species [9, 16]
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