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Pollen morphology and variability of native and alien, including invasive, species of the genus Spiraea L. (Rosaceae) in Poland
The pollen morphology was studied in 25 taxa of the genusSpiraeaL. The aims of this study were to describe the pollen morphology and variability and to determine whether the pollen features of alien, expansive or invasiveSpiraeaspecies differ from those of other taxa. The species ofSpiraeawere analysed for nine quantitative pollen traits as well as the following qualitative traits: the outline, shape and exine ornamentation. In total, 750 pollen grains were measured. Based on the pollen key exine ornamentation features, then individualSpiraeaspecies were distinguished, while the other species formed groups of usually 2–3, up to 8 species. The most important pollen features included length, width and course of grooves and striae, presence or absence of perforations, as well as their number and diameter. The most variable taxa for all the nine biometric traits jointly wereS.×billardii,S.veitchii,S.nipponicaandS.cana. The pollen of the invasiveS.tomentosadiffered from the other taxa studied, unlike the other invasive species (S.douglasiiandS.japonica).
Intra- and interspecific pollen morphology variation of invasive Reynoutria taxa (Polygonaceae) in their response to different habitat conditions
Although understanding the relationship between the reproductive mode and mass-dispersal potential of plants is crucial for studying invasion phenomena, the morphological features of invasive species’ pollen are not well understood. This study examined the pollen morphology and variability of three Reynoutria (knotweed) taxa (R. japonica, R. sachalinensis, R. × bohemica) invasive in Europe, and their reaction to different habitat conditions within seven distinguished habitat types. The pollen was sourced from 95 sites from the taxa’s invasive range in Central Europe. In total, 2850 pollen grains were measured and analysed for 11 quantitative and qualitative features. The pollen of R. sachalinensis was distinguished from that of the other two taxa (reticulate perforate) based on its rugulate and fossulate perforate exine ornamentation. The pollen’s response to various habitat conditions, which was most marked in R. × bohemica, was reflected by pollen size and exine thickness. Our research indicates that pollen availability is not a limiting factor for the sexual reproduction of knotweeds in Central Europe, including Reynoutria japonica, long considered male sterile. The observed presence of male-fertile specimens of R. japonica may enhance the efficiency of generative reproduction in this species throughout its invaded ranges. This finding should be considered when planning actions to control the population of these transformer plant species.
Pollen Morphological Inter- and Intraspecific Variability in Selected Species of Rubus L. (Rosaceae)
Pollen morphology is one of the important vehicles in resolving some taxonomic problems on the family, genera or species level and has become part of the many disciplines and collaborative approaches in plant systematics and evolution. Palynological studies on the large and taxonomically highly complex genus Rubus L. have been limited, particularly concerning pollen variability. The aim of current study was to investigate the scope of inter- and intraspecific variability of the studied species based on pollen morphology, as well as verify taxonomic usefulness of pollen traits in distinguishing the studied taxa. The sixteen native Poland and Europe Rubus species were studied. Over a dozen quantitative and qualitative features of 2100 pollen (70 samples of 30 pollen each) were analyzed. Exine ornamentation and pollen size proved to be most useful pollen traits in the assessment of variability in the studied Rubus species. Pollen traits did not confirm the currently adopted taxonomical division of the genus Rubus into subgenera, sections and series. The greatest interspecific variability was found for traits P, E, Le and d, while variability was lowest in the case of Exp, Exe, P/E, Le/P, d/E, Exp/P and Exe/E. Intraspecific variability was determined by the following features ordered from those least to most variable: P, E, d, Le, d/E, Exp/P, Exp, P/E and Le/P.
How Do Pollen Grains of Convallaria majalis L. Respond to Different Habitat Conditions?
To date, the effect of habitat conditions on the characteristics of pollen has not been extensively investigated; however, it needs to be remembered that it may be highly significant for the quality of their generative reproduction success. It was decided to conduct the analyses on Convallaria majalis as a common species, naturally found in many different forest habitats. Moreover, the investigations covered pollen morphology and for the first time also the variability of pollen grains in this species. The plant material came from 98 natural sites located in Poland, in nine differing forest habitats. In total, 2940 pollen grains were analyzed in terms of five quantitative features (i.e., the length of the longest and shortest polar axes–LA and SA, exine thickness–Ex, the LA/SA and Ex/LA ratios) as well as the following qualitative ones: pollen outline and shape, sulcus type and exine ornamentation. Our studies revealed that the most important pollen characteristics in C. majalis included sulcus type, exine ornamentation, distribution and size of perforations, LA and pollen shape. The study showed the response of pollen to different habitat conditions found in the nine investigated habitats. The Ex/LA ratio and Ex were these pollen characteristics, which exhibited the most marked response to the different habitat conditions. Pollen from two habitats, moist mixed coniferous forest and upland mesic broadleaved forest, exhibited the most distinct characteristics.